Interciew Questions of Windows DHCP Interview

What is dhcp? 

Dynamic Host Configuration Protocol (DHCP) is a network protocol that enables a server to automatically assign an IP address to a computer from a defined range of numbers (i.e., a scope) configured for a given network.

What is the dhcp process for client machine?
 

1. A user turns on a computer with a DHCP client.
2. The client computer sends a broadcast request (called a DISCOVER or DHCPDISCOVER), looking for a DHCP server to answer.
3. The router directs the DISCOVER packet to the correct DHCP server.
4. The server receives the DISCOVER packet. Based on availability and usage policies set on the server, the server determines an appropriate address (if any) to give to the client. The server then temporarily reserves that address for the client and sends back to the client an OFFER (or DHCPOFFER) packet, with that address information. The server also configures the client's DNS servers, WINS servers, NTP servers, and sometimes other services as well.
5. The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know that it intends to use the address.
6. The server sends an ACK (or DHCPACK) packet, confirming that the client has been given a lease on the address for a server-specified period of time.

What is dhcp scope?
 

DHCP scopes are used to define ranges of addresses from which a DHCP server can assign IP addresses to clients.

Types of scopes in windows dhcp ?
 

Normal Scope - Allows A, B and C Class IP address ranges to be specified including subnet masks, exclusions and reservations. Each normal scope defined must exist within its own subnet.
Multicast Scope - Used to assign IP address ranges for Class D networks. Multicast scopes do not have subnet masks, reservation or other TCP/IP options.
Multicast scope address ranges require that a Time To Live (TTL) value be specified (essentially the number of routers a packet can pass through on the way to its destination).
Superscope - Essentially a collection of scopes grouped together such that they can be enabled and disabled as a single entity.

What is Authorizing DHCP Servers in Active Directory?
 

If a DHCP server is to operate within an Active Directory domain (and is not running on a domain controller) it must first be authorized.
This can be achieved either as part of the DHCP Server role installation, or subsequently using either DHCP console or at the command prompt using the netsh tool.
If the DHCP server was not authorized during installation, invoke the DHCP console (Start - All Programs - Administrative Tools - DHCP),
right click on the DHCP to be authorized and select Authorize. To achieve the same result from the command prompt, enter the following command:
netsh dhcp server serverID initiate auth
In the above command syntax, serverID is replaced by the IP address or full UNC name of system on which the DHCP server is installed.

What ports are used by DHCP and the DHCP clients ?
 

Requests are on UDP port 68, Server replies on UDP 67 .

Benefits of using DHCP
 

DHCP provides the following benefits for administering your TCP/IP-based network:
Safe and reliable configuration. DHCP avoids configuration errors caused by the need to manually type in values at each computer. Also, DHCP helps prevent address conflicts caused by a previously assigned IP address being reused to configure a new computer on the network.
Reduces configuration management.

Using DHCP servers can greatly decrease time spent to configuring and reconfiguring computers on your network. Servers can be configured to supply a full range of additional configuration values when assigning address leases. These values are assigned using DHCP options. Also, the DHCP lease renewal process helps assure that where client configurations need to be updated often (such as users with mobile or portable computers who change locations frequently), these changes can be made efficiently and automatically by clients communicating directly with DHCP servers.

The following section covers issues that affect the use of the DHCP Server service with other services or network configurations. Using DNS servers with DHCP Using Routing and Remote Access servers with DHCP Multihomed DHCP servers.

Describe the process of installing a DHCP server in an AD infrastructure?
 

Open Windows Components Wizard. Under Components , scroll to and click Networking Services. Click Details . Under Subcomponents of Networking Services , click Dynamic Host Configuration Protocol (DHCP) and then click OK .

Click Next . If prompted, type the full path to the Windows Server 2003 distribution files, and then click Next. Required files are copied to your hard disk.

How to authorize a DHCP server in Active Directory Open DHCP?
 

In the console tree, click DHCP
. On the Action menu, click Manage authorized servers.
. The Manage Authorized Servers dialog box appears. Click Authorize.
. When prompted, type the name or IP address of the DHCP server to be authorized, and then click OK.

What is DHCPINFORM?
 

DHCPInform is a DHCP message used by DHCP clients to obtain DHCP options. While PPP remote access clients do not use DHCP to obtain IP addresses for the remote access connection, Windows 2000 and Windows 98 remote access clients use the DHCPInform message to obtain DNS server IP addresses, WINS server IP addresses, and a DNS domain name.

The DHCPInform message is sent after the IPCP negotiation is concluded. The DHCPInform message received by the remote access server is then forwarded to a DHCP server. The remote access server forwards DHCPInform messages only if it has been configured with the DHCP Relay Agent.

Describe the integration between DHCP and DNS?
 

Traditionally, DNS and DHCP servers have been configured and managed one at a time. Similarly, changing authorization rights for a particular user on a group of devices has meant visiting each one and making configuration changes.

DHCP integration with DNS allows the aggregation of these tasks across devices, enabling a company's network services to scale in step with the growth of network users, devices, and policies, while reducing administrative operations and costs. This integration provides practical operational efficiencies that lower total cost of ownership.

Creating a DHCP network automatically creates an associated DNS zone, for example, reducing the number of tasks required of network administrators. And integration of DNS and DHCP in the same database instance provides unmatched consistency between service and management views of IP address-centric network services data.

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Access Control Lists (ACLs)

 

Access Control List (ACL) are filters that enable you to control which routing updates or packets are permitted or denied in or out of a network. They are specifically used by network administrators to filter traffic and to provide extra security for their networks. This can be applied on routers (Cisco).

ACLs provide a powerful way to control traffic into and out of your network; this control can be as simple as permitting or denying network hosts or addresses.  You can configure ACLs for all routed network protocols.

The most important reason to configure ACLs is to provide security for your network. However, ACLs can also be configured to control network traffic based on the TCP port being used.

 How ACLs work

A router acts as a packet filter when it forwards or denies packets according to filtering rules. As a Layer 3 device, a packet-filtering router uses rules to determine whether to permit or deny traffic based on source and destination IP addresses, source port and destination port, and the protocol of the packet. These rules are defined using access control lists or ACLs.

 To simplify how ACL or a router uses packet filtering work, imagine  a guard stationed at a locked door. The guard's instruction is to allow only people whose names appear on a quest list to pass through the door. The guard is filtering people based on the condition of having their names on the authorized list.

When a packet arrives at the router, the router extracts certain information from the packet header and makes decisions according to the filter rules as to whether the packet can pass through or be dropped. Packet filtering process works at the Network layer of the Open Systems Interconnection (OSI) model, or the Internet layer of TCP/IP.

Books on Cisco Networking, Certifications and Exam Resources

 Why use ACLs

*   Limits network traffic to increase network performance.

*   ACLs provides traffic flow control by restricting the delivery of routing updates.

*   It can be used as additional security.

*   Controls which type of traffic are forwarded or blocked by the router.

*   Ability to control which areas a client access.

Types of Access Control Lists

Standard access-list

Standard access lists create filters based on source addresses and are used for server based filtering. Address based access lists distinguish routes on a network you want to control by using network address number (IP). Address-based access lists consist of a list of addresses or address ranges and a statement as to whether access to or from that address is permitted or denied.

Example of the command syntax for configuring a standard numbered IP ACL:

R1(config)# access-list {1-99} {permit | deny} source-addr [source-wildcard]

i.         The first value {1-99} specifies the standard ACL number range.
ii.       The second value specifies whether to permit or deny the configured source IP address traffic.
iii.      The third value is the source IP address that must be matched.
iv.     The fourth value is the wildcard mask to be applied to the previously configured IP address to indicate the range.
 

Extended access lists

Extended access lists create filters based on source addresses, destination addresses, protocol, port number and other features and are used for packet based filtering for packets that traverse the network.

Example of the command syntax for configuring an extended numbered IP ACL:
 Router(config)# access-list {100-199} {permit | deny} protocol source-addr [source-wildcard] [operator operand] destination-addr [destination-wildcard] [operator operand] [established]

i.   Like the standard ACLs, the first value {100-199 or 2000 - 2699} specifies the ACL number range.
ii.  The next value specifies whether to permit or deny according to the criteria that follows.
iii. The third value specifies protocol type ( IP, TCP, UDP, or other specific IP sub-protocols). The source IP address and wildcard mask determine traffic source. The destination IP address and its wildcard mask are used to indicate the final destination of the network traffic. When the destination IP address and mask are configured, the port number  must be specified to match, either by number or by a well-known port name, otherwise all traffic to that destination will be dropped.

Standard and Extended access lists can be applied base on the use of ip access-list command.
Access lists use the deny or permit statement to define which packet is allowed or denied entry into a server or network.

Masks

Masks are used with IP addresses in IP ACLs to specify what should be permitted and denied. Masks in order to configure IP addresses on interfaces start with 255 and have the large values on the left side, for example, IP address 172.16.2.14 with a 255.255.255.0 mask. Masks for IP ACLs are the reverse, for example, mask 0.0.0.255. This is sometimes called an inverse mask or a wildcard mask. When the value of the mask is broken down into binary (0s and 1s), the results determine which address bits are to be considered in processing the traffic. A 0 indicates that the address bits must be considered (exact match); a 1 in the mask is a "no".
Note these ACL equivalents.
· The source/source-wildcard of 0.0.0.0/255.255.255.255 means "any".
· The source/wildcard of 10.1.1.2/0.0.0.0 is the same as "host 10.1.1.2".
If you subtract 255.255.255.0 (normal mask) from 255.255.255.255, it yields 0.0.0.255.
Read about Wildcards
The command below defines an ACL that permits this network 192.168.1.0 0.0.0.255.
access-list acl_permit permit ip 192.168.1.0 0.0.0.255
Inbound traffic to the router is compared to access lists entries based on the order that the entries occur in the router. The router looks through the entries until it has a match. If the router found no match when it reaches the end of the list, the traffic is denied. For this reason, you should have the frequently hit entries at the top of the list. There is an implied deny for traffic that is not permitted. Single-entry access lists with only one deny entry has the effect of denying all traffic. You must have at least one permit statement in an ACL or all traffic is blocked.
Access lists implicitly deny all access that is not expressly permitted. The following line is auto-appended to all access-lists:

deny ip any any

If it is desirable to over-ride this implicit denial statement, enter a permit ip any any statement as the last entry in the access-list.

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Troubleshooting Frame Relay Configuration

After configuring your network, it’s considered a good idea to verify that your configuration is working. This can be accomplished by using the ping and other troubleshooting methods.

If your verification procedure indicates that your Frame Relay configuration is not working properly, you need to troubleshoot the configuration.
The following Troubleshooting methods can very helpful:

i.                     Debug frame-relay lmi
ii.                   Show Interfaces
iii.                  Show frame-relay pvc
iv.                 Show frame-relay map
v.                  Show frame-relay lmi

i. Debug frame-relay lmi:  Use the debug frame-relay lmi command to verify the operational status of the router and the Frame Relay switch. This will show you if the LMI packets are being sent and received properly.
Example of an output from an LMI exchange.

• "out" is an LMI status message sent by the router.
• "in" is a message received from the Frame Relay switch.
• A full LMI status message is a "type 0".
• An LMI exchange is a "type 1".
• "dlci 102, status 0x2" means that the status of DLCI 102 is active.

When an Inverse ARP request is made, the router (DTE) updates its map table with three possible LMI connection states. These are active state, inactive state, and deleted state

• ACTIVE States shows a successful end-to-end (DTE to DTE) circuit.
• INACTIVE State shows a successful connection to the frame Relay switch (DTE to DCE) without the remote DTE detected on the other end of the PVC. This can occur due to incorrect configuration on the switch.
• DELETED State means that the router (DTE) is configured for a DLCI the frame relay switch does not recognize as valid for that interface.

The values of the status field are as follows:

• 0x0 - The switch has this DLCI computed, but for some reason it is unusable. The reason could be that the other end of the PVC is down.
• 0x2 – this indicates that the Frame Relay switch has the DLCI and everything is working properly.
• 0x4 – this means that the Frame Relay switch does not have this DLCI configured for the router, but that it was programmed at some point in the past. This could also be caused by the DLCIs being reversed on the router, or by the PVC being deleted by the service provider in the Frame Relay cloud.

ii.  Frame Relay Interfaces
After configuring Frame Relay PVC and you are troubleshooting network issue, verify that Frame Relay is operating correctly on that interface using the show interfaces {interface number} command.
The show interfaces command displays how the encapsulation is set up, along with useful Layer 1 and Layer 2 status information, including:
LMI type
LMI DLCI

Frame Relay DTE/DCE type

iii. Show frame-relay lmi: This command is used to verify some LMI statistics in the output, look for any non-zero "Invalid" items. This helps isolate the problem to a Frame Relay connectivity issue between the carrier's frame relay switch and your router (DTE).
The figure below displays a sample output that shows the number of status messages exchanged between the local router and the local Frame Relay switch.

Router1#sho frame-relay lmi

LMI Statistics for interface Serial0/0/0 (Frame Relay DTE) LMI TYPE = ANSI

 Invalid Unnumbered info 0      Invalid Prot Disc 0

Invalid dummy Call Ref 0       Invalid Msg Type 0

 Invalid Status Message 0       Invalid Lock Shift 0

 Invalid Information ID 0       Invalid Report IE Len 0

 Invalid Report Request 0       Invalid Keep IE Len 0

 Num Status Enq. Sent 36        Num Status msgs Rcvd 36

Num Update Status Rcvd 0       Num Status Timeouts 16

iv. Show frame-relay pvc: This command is used to verify the PVC status. The show frame-relay pvc command displays the status of all the PVCs configured on the router You can also use the show frame-relay pvc [interfaceinterface] [dlci] command to view a particular PVC and traffic statistics. This command is also useful for viewing the number of BECN and FECN packets received by the router. The PVC status can be active, inactive, or deleted.

Router1#sho frame-relay pvc

PVC Statistics for interface Serial0/0/0 (Frame Relay DTE)

DLCI = 102, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0/0/0

input pkts 14055       output pkts 32795        in bytes 1096228

out bytes 6216155      dropped pkts 0           in FECN pkts 0

in BECN pkts 0         out FECN pkts 0          out BECN pkts 0

in DE pkts 0           out DE pkts 0

out bcast pkts 32795   out bcast bytes 6216155

v. Show frame-relay map: This command is used to verify whether the frame-relay inverse-arp command resolved a remote IP address to a local DLCI. Use the show frame-relay map command to display the current map entries and information about the connections.

Router1#show frame-relay map
Serial0/0/0 (up): ip 10.1.1.2 dlci 102 (0x66, 0x1860), static, broadcast, CISCO, status defined, active

The output below explains the following information:

10.1.1.2 is the IP address of the remote router, dynamically learned via the Inverse ARP process.

102 is the decimal value of the local DLCI number.

0x66 is the hex conversion of the DLCI number, 0x66 = 102 decimal.

0x1860 is the value, as it would appear on the wire because of the way the DLCI bits are spread out in the address field of the Frame Relay frame.

Broadcast/multicast is enabled on the PVC.

PVC status is active.

Use the clear frame-relay-inarp command to clear dynamically created Frame Relay maps that are created using Inverse ARP.

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IP Routing

IP routing is the process use by a router to forward packets towards destination network as found in the routing table, which is created by routing algorithms or routing protocols.
A router makes decisions based upon the destination IP address of a packet. Routers don’t care about hosts in a network, but networks and the best possible way to reach them. All network devices along the way use the destination IP address to send the packet in the right direction to reach its destination. To make the correct decisions, routers must learn how to reach remote networks. Routers use either dynamic routing - this information is learned from other routers, or static routing - a network administrator configures information about remote networks manually.
Although it’s deemed necessary for every device in the network to be assigned a unique IP address, but this is not sufficient for them to communicate. It’s the work of a router to acts as a sort of traffic director to all packet destined to a destination.
In summary, routers route traffic to all networks in your internetwork. For a router to be able to do this, it must know the following:

i.    Destination address

ii.   Possible routes to all networks

 iii. Neighboring routers from which it will learn about remote networks

iv. The best route to reach a network

v. How to maintain and verify routing information.

 

Example below shows how a router uses information in its routine table to make decisions:

 

 

 

R2#show IP route
[Output omitted]
Gateway of last resort is not set
C   192.168.1.32/27 is directly connected, fastEthernet0/1
C   192.168.1.0/27 is directly connected, fastEthernet0/2
C   10.10.1.0/30 is directly connected, serial 0/0/0
The C in the routing table means the networks are directly connected. The remote networks are not found and displayed in the routine table because, we have not added a routing protocol – such as RIP, EIGRP, OSPF etc. etc or configured Static routes.
Looking at the output above, when the network router receive a packet with the destination address of 192.168.1.10, the router will send the packet to interface fastEthernet0/2, and this interface will frame the packet and then send it out on the network segment to Network B.

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Configuring PPP with Authentication

PAP and CHAP

One of the many features of PPP is that it performs Layer 2 authentication in addition to other layers of authentication, encryption, access control, and general security procedures.
Before Network Layer protocols are allowed to transmit over a link, PPP will spell out an extensible link control protocol that will make room for negotiation of an authentication protocol. This is defined in the RFC 1134.
The authentication phase of a PPP session is optional. If used, you can authenticate the peer after the LCP establishes the link and choose the authentication protocol. If it is used, authentication takes place before the Network layer protocol configuration phase begins.

The authentication options require that the calling side of the link enter authentication information. This helps to ensure that the user has the permission of the network administrator to make the call. Peer routers exchange authentication messages

 

SUMMARY
After enabling CHAP or PAP authentication, or both, the local or HQ router requires the remote device to prove its identity before allowing data traffic to flow.
i.  PAP authentication requires the remote device to send a username and password to be checked against a matching entry in the local username database or in the remote TACACS/TACACS+ database.

ii.  CHAP authentication sends a challenge to the remote device. The remote device must encrypt the challenge value with a shared secret and return the encrypted value and its name to the local router in a response message. The local router uses the name of the remote device to look up the appropriate secret in the local username or remote TACACS/TACACS+ database. It uses the looked-up secret to encrypt the original challenge and verify that the encrypted values match.

 

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How to configure PPP on Cisco Router

You can configure point-to-point encapsulation, software compression, link quality monitoring, load balancing across links (multilinks) on R1, R2 and R3 serial interface below.

Before you actually configure PPP on a serial interface, we will look at the commands and the syntax of these commands as shown below. This series of examples shows you how to configure PPP and some of the options.

 

 

 

1: How to enable PPP on an Interface

To set PPP as the encapsulation method used by a serial or ISDN interface, use the encapsulation ppp interface configuration command.
The following example enables PPP encapsulation on serial interface 0/0/0:

R1#config t

R1(config)#interface se 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#end

 The encapsulation ppp command has no arguments, however, you must first configure the router with an IP routing protocol (RIP, EIGRP or OSPF) to use PPP encapsulation. You should recall that if you do not configure PPP on a Cisco router, the default encapsulation for serial interfaces is HLDC.

 2: How to configure Compression

You can configure point-to-point software compression on serial interfaces after you have enabled PPP encapsulation. Because this option invokes a software compression process, it can affect system performance. If the traffic already consists of compressed files (.zip, .tar, or .mpeg, for example), do not use this option.
To configure compression over PPP, enter the following commands:

R1(config)#interface serial 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#compress [predictor | stac]

R1(config-if)#end

 

3: How to configure Link Quality Monitoring

One of the primary functions of LCP when establishing a PPP session includes testing of a link to determine whether the link quality is sufficient to use Layer 3 protocols. The command ppp quality {percentage} ensures that the link meets the quality requirement you set; otherwise, the link closes down.

 

 

 

 

 

How Link Percentage is calculated

The percentages are calculated for both incoming and outgoing directions. The outgoing quality is calculated by comparing the total number of packets and bytes sent to the total number of packets and bytes received by the destination node. The incoming quality is calculated by comparing the total number of packets and bytes received to the total number of packets and bytes sent by the destination node.
If the link quality percentage is not maintained, the link is deemed to be of poor quality and is taken down. Link Quality Monitoring (LQM) implements a time lag so that the link does not bounce up and down.
Use the configuration commands below to monitor the data traffic on the link and avoids frame looping:

R1(config)#interface serial 0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#ppp quality 80

R1(config-if)#end

Use the no ppp quality command to disable LQM.

 

4:How to Configure Load Balancing Across Links (MultiLinks)
Multilink PPP (also referred to as MP, MPPP, MLP, or Multilink) provides a method for spreading traffic across multiple physical WAN links while providing packet fragmentation and reassembly, proper sequencing, multivendor interoperability, and load balancing on inbound and outbound traffic.
MPPP allows packets to be fragmented and sends these fragments simultaneously over multiple point-to-point links to the same remote address. The multiple physical links come up in response to a user-defined load threshold. MPPP can measure the load on just traffic into the network, or on just traffic going out, but not on the combined load of both inbound and outbound traffic.
Use the following commands to perform load balancing across multiple links:

R1#config t

R1(config)#interface se0/0/0

R1(config-if)#encapsulation ppp

R1(config-if)#ppp multilink

R1(config-if)#end

The multilink command has no arguments. To disable PPP multilink, use the no ppp multilink command

Configuring PPP with Authentication (PAP and CHAP)

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  PPP Configuration Options

PPP can be configured to support various functions including:
Authentication
you can configure PPP authentication using either PAP or CHAP. Peer routers exchange authentication messages. Two authentication choices are Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).
Compression
Compression in a way of using either Stacker or Predictor, this increases the effective throughput on PPP connections by reducing the amount of data in the frame that must travel across the link. The protocol decompresses the frame at its destination. Two compression protocols available in Cisco routers are Stacker and Predictor. see how to configure your network links with compression here.
PPP Callback
To enhance security, Cisco IOS Release 11.1 and later offers callback over PPP. With this LCP option, a Cisco router can act as a callback client or a callback server. The client makes the initial call, requests that the server call it back, and terminates its initial call. The callback router answers the initial call and makes the return call to the client based on its configuration statements. The command is ppp callback [accept | request].

Multilink

Multilink combines two or more channels to increase the WAN bandwidth: Cisco IOS Release 11.1 and later supports multilink PPP. This alternative provides load balancing over the router interfaces that PPP uses. Multilink PPP (also referred to as MP, MPPP, MLP, or Multilink) provides a method for spreading traffic across multiple physical WAN links while providing packet fragmentation and reassembly, proper sequencing, multivendor interoperability, and load balancing on inbound and outbound traffic.

Error detection

Error detection identifies fault conditions. The Quality and Magic Number options help ensure a reliable, loop-free data link. The Magic Number field helps in detecting links that are in a looped-back condition. Until the Magic-Number Configuration Option has been successfully negotiated, the Magic Number must be transmitted as zero. Magic numbers are generated randomly at each end of the connection.

How to Configure PPP on Cisco router

How to Configure PAP and CHAP Authentication

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Point-to-Point (PPP)

What is PPP?
Point-to-Point connection is one of the most common types of WAN connection. PPP connections are used to connect LANs to service provider WANs, and to connect LAN segments within an organisation network. A LAN-to-WAN point-to-point connection is also referred to as a serial connection or leased-line connection, because the lines are leased from a carrier (usually a telephone company) and are dedicated for use by the company leasing the lines.
Simply, when you establish a connection to your ISP (Internet Service Provider) through a modem. The connection between the ISP and you make up two points on the network. Therefore, the protocol that is used for establishing this connectivity between the two of you is the Point-to-Point Protocol or the PPP.
Note: The default serial encapsulation method when you connect two Cisco routers is HDLC. This means, Cisco HDLC can only work with other Cisco devices. However, when you need to connect to a non-Cisco router, you should use PPP encapsulation. This is one of many advantages to using PPP it is not proprietary.
PPP can be used over twisted pair, fibre-optic lines, and satellite transmission. PPP provides transport over ATM, Frame Relay, ISDN and optical links. For security, PPP allows you to authenticate or secure connections using either Password Authentication Protocol (PAP) or the more effective Challenge Handshake Authentication Protocol (CHAP).
PPP is used to carry out the following functions

• Data Encapsulations: this is a method used to encapsulate multi-protocol datagrams. Different network-layer protocols are simultaneously transported and encapsulated over the same link, the flexibility of the PPP design enables it to be compatible to most supporting network devices.
• Link Control Protocol: The LCP is used to establish, configure, and test the data link connection. It’s flexible in handling different sizes of packets, detect a looped-back link, configuration errors, and terminate the link.
• Network Control Protocol: NCP is used for establishing and configuring different Network layer protocols. PPP enables the simultaneous use of multiple Network layer protocols.  Some of the more familiar NCPs are:

i.        Internet Protocol Control Protocol
ii.       AppleTalk Control Protocol
iii.     Novell IPX Control Protocol
iv.     Cisco Systems Control Protocol
v.      SNA Control Protocol
vi.     Compression Control Protocol.

PPP Configuration Options

How to Configure PPP on Cisco router

How to Configure PPP with Authentication (PAP and CHAP)

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Crossover UTP Cables

Crossover UTP Cables

Use a crossover cable when connecting the same type of network device.

For two devices to communicate through a cable that is directly connected between the two, the transmit terminal of one device needs to be connected to the receive terminal of the other device.

The cable must be terminated so the transmit pin, Tx, taking the signal from device A at one end, is wired to the receive pin, Rx, on device B. Similarly, device B's Tx pin must be connected to device A's Rx pin. If the Tx pin on a device is numbered 1, and the Rx pin is numbered 2, the cable connects pin 1 at one end with pin 2 at the other end. These "crossed over" pin connections give this type of cable its name, crossover

 

To achieve this type of connection with a UTP cable, one end must be terminated as EIA/TIA T568A pinout, and the other end terminated with T568B pinout.

Note:

Use crossover cables to directly connect the following devices on a LAN:

a.  Switch to Switch

b.  Switch to Hub

c.  Hub to Hub

d.  Router to Router Ethernet port connection

e.  Computer to Computer

f.  Computer to a Router Ethernet port

Crossover cables have a T568A Termination at one end ans a T568B at the other end.

 

 

 

 

 

Straight through Cables

 Cabling Network Devices

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Straight-through UTP Cables

Use a straight-through cable when connecting different types of network devices.

A straight-through cable has connectors on each end that are terminated the same in accordance with either the T568A or T568B standards.

Identifying the cable standard used allows you to determine if you have the right cable for the job. More importantly, it is a common practice to use the same color codes throughout the LAN for consistency in documentation.

Note:

Use straight-through cables for the following connections:

a.  Switch to a router Ethernet port

b.  Computer to switch

c.  Computer to hub

Cross-Over Cable

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Cabling Network Devices

Types of Cables (Media)

Choosing the right cable necessary to make a successful Local Area Network (LAN) or Wide Area Networking (WAN) connection requires deliberation of the different media or cable types. For the benefit of beginners, there are many different Physical layer implementations that support multiple cable types:
UTP (Category 5, 5e, 6, and 7)
Fibre-optics
Wireless
Each cable type has its advantages and disadvantages. Some of the factors to consider are:
Cable length – how far will the cables have to go around the room or building?
Cost - Does the budget allow for using a more expensive media type?
Bandwidth – this is one of the criteria to focus your thoughts on. Does the technology used with the Cable provide adequate bandwidth?
Susceptible to Electromagnetic interference also called radio frequency interference (EMI/RFI) - Is the local environment going to interfere with the signal?
UTP cabling connections are specified by the Electronics Industry Alliance/Telecommunications Industry Association (EIA/TIA).

RJ-45

The RJ-45 connector is the male part crimped on the end of the cable. When viewed from the front, the pins are numbered from 8 to 1. When viewed from above with the opening gate facing you, the pins are numbered 1 through 8, from left to right. The standard lengths for this cable are 1.83m (6ft) and 3.05m(10ft). This orientation is important to remember when identifying a cable.

RJ45

RJ45 Top View 

                                                A                                       B          

                                                                 RJ45 Cable Orientation

                                                                                

                                                                                     A

Pin	Pin	Function	Wire Color
1	3	Transmit	White/Green
2	3	Transmit	Green
3	2	Receive	White/Orange
4	1	No used	Blue
5	1	Not used	White/Blue
6	2	Received	Orange
7	4	Not used	White/Brown
8	4	No used	Brown

                                                                B

Pin	Pin	Function	Wire Color
1	2	Transmit	White/Orange
2	2	Transmit	Orange
3	3	Receive	White/Green
4	1	Not used	Blue
5	1	Not used	White/Blue
6	3	Receive	Green
7	4	Not used	White/Brown
8	4	Not used	Brown

      

      

       MDI & MDIX Cables

 

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The Internet - A Network of Networks

Although there are benefits to using a LAN or WAN, most of us need to communicate with a resource on another network, outside of our local office or organization. Examples of this type of communication include:
*  Sending an e-mail to a friend in another country
*  Accessing news or products on a website
*  Getting a file from a neighbour’s computer
*  Sending Instant messaging with a relative in another city
*  Looking up sports news on a cell phone

Internetwork

To meets these human communication needs. Internetwork had to be created, Internetworks is created by the interconnection of networks belonging to Internet Service Providers (ISPs). Some of these interconnected networks are owned by large public and private organizations, such as government agencies or industrial enterprises. The most well-known and widely used publicly accessible Internetwork is the Internet.
The Internet is These ISP networks connect to each other to provide access for millions of users all over the world. Ensuring effective communication across this diverse infrastructure requires the application of consistent and commonly recognized technologies and protocols as well as the cooperation of many network administration agencies.

Intranet

The term intranet is often used to refer to a private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization.

Note: A connection of two or more data networks forms an Internetwork - a network of networks The following terms can be used interchangeably: Internetwork, data network, and network. It is also common to refer to an internetwork as a data network - or simply as a network - when considering communications at a high level. The usage of terms depends on the context at the time and terms may often be interchanged.

 

                                                         Interconnection of Networks

 

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How to Filtering Access by MAC Address

Filtering Access by MAC Address

Wireless routers like the Linksys by Cisco wireless range can be used not only for routing traffic between networks and computer in your home or office;it can also be used as a Firewall. As you must know; every network device is identified by a physical address also known as MAC address. You can use your wireless router to filter or control access to the internet or programs by listing and preventing the MAC addresses of devices connected to the wireless router.

To filter MAC addresses, follow this step:

 

1. Click the Wireless tab
2. Click Wireless MAC Address filter
3. Click Enable
4. Click Permit Only PCs listed to access the wireless network
5. Click wireless Client or Edit MAC Filter List
When MAC address filter list window appears,enter the address of each network adapter in your home or office you want to prevent from accessing the network

Click SaveSetting at the bottom of the window.

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How To Configure The Basic Wireless Settings (Linksys Wireless B, G, N)

 When you access the web-based utility, the first screen you see is the Basic Setup screen.

Click the Wireless tab and then select the Basic Wireless Settings tab.To configure the basic Wireless Settings, click on each tab to perform your configuration:
i.    Network Mode

When you click the network mode bar, a drop down menu will be display all devices in your wireless LAN.

*  If you have the Linksys Wireless-N, Wireless-G, and 802.11b devices in your network, select Mixed, the   default setting.

*  If you have Wireless-G and 802.11b devices, select BG-Mixed.

*  If you have only Wireless-N devices, select Wireless-N Only. If you have only Wireless-G devices, select Wireless-G Only. If you have only Wireless-B devices, select Wireless-B Only.

*  Select Disable to disable your wireless networking mode.

ii. Network Name (SSID)

The SSID is the network name shared among all points in a wireless network. The SSID must be the same for all devices in the wireless network. The SSID is case-sensitive and must not be more than 32 characters in length (use any of the characters on the keyboard). It is recommended that you change the default SSID to a your own unique name to enhance security.

iii.  Radio Band

 *  If you are using Wireless-N, Wireless-G, and Wireless-B devices in your network, select Auto (default).     This is recommended for best performance in your network.

*  If you are using Wireless-N devices only, select Wide - 40MHz Channel.

For Wireless-G and Wireless-B networking only, select Standard - 20MHz Channel.

iv. Wide Channel

 If you selected Wide - 40MHz Channel for the Radio Band setting, this setting is available for your primary Wireless-N channel. Select any channel from the drop-down menu.

v.  Standard Channel
 Select the channel for Wireless-N, Wireless-G, and Wireless-B networking. If you selected Wide - 40MHz Channel for the Radio Band setting, the standard channel is a secondary channel for Wireless-N.

  vi.   SSID Broadcast

 When you are scanning your local area for wireless networks to connect with, you can detect the SSID broadcast by the access point. To broadcast the SSID, select Enabled (default). Select Disabled If you do not want to broadcast the SSID. When you have finished making changes to this screen, click the Save Settings button.

Click the Cancel Changes button to undo your changes. Click Help for more information

How to Filter Network Access by MAC Address

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How to Install and Configure your Wireless Router or Access Points

On the following pages, you will learn how to configure a wireless router or access point. This includes:

i.  How to set the SSID

ii. Enable security

iii. Configure the channel

iv.  Adjust the power settings of a wireless access point.

We will also look at how to back up and restore your configuration settings on a wireless access point.
Most access points have been designed to function with the default or factory settings. It is recommended to change the default configurations.
After confirming your wired network connectivity, and the access point installed, you will now configure it.

In the following examples we will be using the Linksys WRT300N multifunction device, it also an access point.

 

Use these steps for configuring the Linksys WRT300N and most linksys wireless access points:
Make your PC is connected to the access point via a wired connection, and access the web utility with a web browser. To access the web-based utility of the access point, launch Internet Explorer, and enter the WRT300N default IP address, 192.168.1.1, in the address field.
 Press the Enter key.

1.      A screen display prompting you for your username and password. Leave the Username field blank.

 

2. Enter admin in the Password field (default settings for a Linksys WRT300N). If the device has already been configured, the username and password may have been changed.

 

3.      Click OK to continue.

For a basic network setup, we will be learning how to use the following screens

Setup, Management, and Wireless buttons:

i.  Setup – on this screen you will enter your basic network settings (IP address).

ii. Management –start by clicking the Administration tab and then select the Management screen. The default password is admin. To secure the access point, change the password from its default.

 

iii.  Wireless – This is where you make changes of the default SSID. Select the level of security in the Wireless Security tab and complete the options for the selected security mode.

 

When you have finished making changes to a screen, click the Save Settings button, or click the Cancel Changes button to undo your changes. For information on a tab, click Help. We will go through these steps one after the other.

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Wireless LAN (WLAN)

There are different network infrastructures (wired LAN, Service Provider Networks) that allows mobility, but in a business environment, the most important is the wireless LAN (WLAN). Most modern business networks rely on switch-based LANs for day-to-day operation inside the office.

Productivity is no longer restricted to a fixed work location or a defined time period. People now expect to be connected at any time and place, (you are in when you are out) from the office to the airport or even the home. Traveling employees used to be restricted to pay phones for checking messages and returning a few phone calls between flights. Now employees can check e-mail, voice mail, and the status of products on personal digital assistants (PDAs) while at many temporary locations.

Wireless LAN  and Wired (Ethernet) LAN

Wireless LANs share a similar origin with Ethernet LANs. The IEEE has adopted the 802 LAN/MAN portfolio of computer network architecture standards. The two dominant 802 working groups are 802.3 Ethernet and 802.11 wireless LAN. However, there are important differences between the two.
WLANs use radio frequencies (RF) instead of cables at the Physical layer and MAC sub-layer of the Data Link layer. In comparison to cable, RF has the following characteristics:
i.          RF does not have boundaries, such as the limits of a wire in a sheath. The lack of such a boundary allows data frames traveling over the RF media to be available to anyone that can receive the RF signal.
ii.         RF is unprotected from outside signals, whereas cable is in an insulating sheath. Radios operating independently in the same geographic area but using the same or a similar RF can interfere with each other.
iii.        RF transmission is subject to the same challenges inherent in any wave-based technology, such as consumer radio. For example, as you get further away from the source, you may hear stations playing over each other or hear static in the transmission. Eventually you may lose the signal all together. Wired LANs have cables that are of an appropriate length to maintain signal strength.
iv.        RF bands are regulated differently in various countries. The use of WLANs is subject to additional regulations and sets of standards that are not applied to wired LANs.
WLANs connect clients to the network through a wireless access point (AP) instead of an Ethernet switch.
WLANs connect mobile devices that are often battery powered, as opposed to plugged-in LAN devices. Wireless network interface cards (NICs) tend to reduce the battery life of a mobile device.
WLANs support hosts that contend for access on the RF media (frequency bands). 802.11 prescribes collision-avoidance instead of collision-detection for media access to proactively avoid collisions within the media.
WLANs use a different frame format than wired Ethernet LANs. WLANs require additional information in the Layer 2 header of the frame.
WLANs raise more privacy issues because radio frequencies can reach outside the facility.
802.11 wireless LANs extend the 802.3 Ethernet LAN infrastructures to provide additional connectivity options. However, additional components and protocols are used to complete wireless connections.
In an 802.3 Ethernet LAN, each client has a cable that connects the client NIC to a switch. The switch is the point where the client gains access to the network.

In a wireless LAN, each client uses a wireless adapter to gain access to the network through a wireless device such as a wireless router or access point.

 How to Install and Configure your Wireless Router or Access Points

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LAN Design.

When designing a LAN that satisfies the needs of a small- or medium-sized business, your plan is more likely to be successful if a hierarchical design model is used. Compared to other network designs, a hierarchical network is easier to manage and expand, and problems are solved more quickly.

Hierarchical network design involves dividing the network into discrete layers. Each layer provides specific functions that define its role within the overall network. By separating the various functions that exist on a network, the network design becomes modular, which facilitates scalability and performance. The typical hierarchical design model is broken up in to three layers: access, distribution, and core. An example of a three-layer hierarchical network design is displayed in the figure below.

                                                     Hierarchical Network Design

                                         

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LAN (Local Area Network)

A LAN (Local Area Network) is an individual network that covers a single geographical area, providing networking services and applications to people within a common managerial structure, such as a single business, campus or region.

A LAN is usually administered by a single organization. The administrative control that governs the security and access control policies are enforced on the network level. LANs and WANs are very useful to individual organizations. They connect the users within the organization. They allow many forms of communication including exchange e-mails, corporate training, and other resource sharing.

Cisco Networking Books and Exam Resources

Forum Discussion

Communication with data, voice, and video is critical to business survival. Consequently, a properly designed LAN is a fundamental requirement for doing business today. You must be able to recognize a well-designed LAN and select the appropriate devices to support the network specifications of a small- or medium-sized business.

                   

 LAN Design

 Wireless LAN

 The Internet - A Network of Networks

 Cabling Network Devices

  Straight Through Cables

  Cross Over Cables

 Point-to-Point (PPP)

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