1) Enable EIGRP and define the autonomous system with the router eigrp {as-num} global configuration command. The as-num value must be matched on all EIGRP routers within an autonomous system or an EIGRP routing domain.
2) Specify the networks that belong to the EIGRP autonomous system with the network {ip-addr} [wildcast-mask] router subcommand. The ip-addr can be either the network address, the subnet, or the address of an interface. It determines which links to advertise routing updates, which links to listen and process routing updates, and which networks to be advertised in routing updates. The wildcard-mask is an optional inverse mask used to determine how to interpret the ip-addr. It contains wildcard bits, where 0 is a match and 1 is don’t care. Ex: 0.0.0.255 indicates an exact match in the first 3 bytes.
Note: If the optional wildcard-mask is not being specified, the EIGRP process assumes that all directly connected networks that are part of the major network will participate in the EIGRP routing process, and EIGRP will attempt to establish EIGRP neighbor relationship for each interface that is part of the Class A, B, or C network. Use the wildcard-mask to identify an IP address, a subnet, or a network. Ex: Use the mask 0.0.0.0 if specifying an interface to be participated in the EIGRP routing process. The combination of 0.0.0.0 255.255.255.255 matches all interfaces on a router.
Note: The network 0.0.0.0 EIGRP router subcommand is equivalent to the network 0.0.0.0 255.255.255.255 EIGRP router subcommand. However, configuring the combination of 0.0.0.0 0.0.0.0 will be automatically changed to 0.0.0.0 255.255.255.255.
3) When configuring EIGRP on WAN links, remember to define the appropriate bandwidth value for the links for EIGRP to perform metric and route computations precisely. For serials interfaces (eg: PPP and HDLC), set the bandwidth to match the line speed. For Frame Relay point-to-point interfaces, set the bandwidth of the subinterfaces to their corresponding provisioned CIRs. For Frame Relay multipoint interfaces, set the bandwidth to the sum of all CIRs. The bandwidth {kbps} interface subcommand defines the bandwidth of a particular interface. The bandwidth and delay interface subcommands only configures informational parameters for EIGRP to make better metric calculation, they are unable to adjust the actual bandwidth and delay of an interface to achieve better performance. It is recommended to use the bandwidth command over the delay command whenever possible, because it is must easier to get the desired result.
Sample EIGRP Network
EIGRP configuration on RT1, RT2, and RT3:
RT1(config)#router eigrp 100 RT1(config-router)#network 10.1.0.0 RT1(config-router)#network 10.2.0.0 RT1(config-router)#network 172.16.1.0 RT1(config-router)#network 172.16.2.0 RT1(config-router)#no auto-summary RT1(config-router)#end RT1#sh run | b router eigrp router eigrp 100 network 10.0.0.0 network 172.16.0.0 no auto-summary ! ---------------------------------------------------------------------- RT2(config)#router eigrp 100 RT2(config-router)#network 172.16.1.0 0.0.0.255 RT2(config-router)#network 172.16.3.0 0.0.0.255 RT2(config-router)#network 192.168.1.0 RT1(config-router)#no auto-summary RT2(config-router)#end RT2#sh run | b router eigrp router eigrp 100 network 172.16.1.0 0.0.0.255 network 172.16.3.0 0.0.0.255 network 192.168.1.0 no auto-summary ! ---------------------------------------------------------------------- RT3#sh run | b router eigrp router eigrp 100 network 172.16.2.0 0.0.0.255 network 172.16.3.0 0.0.0.255 no auto-summary !Note: The network {classful-network-addr} router subcommand is a classful command, it will change the network number entered along with the command to its classful entry or major network number. Ex: 10.1.1.0 > 10.0.0.0; 172.16.1.0 > 172.16.0.0.
Wildcard mask is not used in RT1 EIGRP configuration. All RT1 interfaces that are part of network 10.0.0.0/8 and network 172.16.0.0/16 are participating in the EIGRP routing process.
Note: Network 192.168.1.0/24, a RT2’s directly connected network, is not configured in RT1, as RT1 does not have any interface resides in that network.
RT2 EIGRP configuration uses wildcard mask to determine which directly connected interfaces to participate in the EIGRP routing process. In this case, all the 3 RT2 interfaces are participating in the EIGRP routing process.
RT3 EIGRP configuration also uses the wildcard masks, as it connects to an external router, and EIGRP should not run over there. RT3 has 3 interfaces of 172.16.0.0 Class B network. Without using wildcard mask, RT3 would send EIGRP to the external network, which would waste bandwidth and CPU resources as well as provide unnecessary information to the network. With the configuration above, RT3 would only establish a relationship with EIGRP routers from interfaces that are part of network 172.16.2.0/24 and 172.16.3.0/24.
No comments:
Post a Comment