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In last week's article, I wrote about configuring route redistribution on Cisco
routers. Route redistribution is used when multiple routers need to exchange
routing information. This week, I will be going through a scenario that will
configure basic route redistribution.
The lab environment consists of
seven routers that are split among network areas routed by RIP, EIGRP, and OSPF
respectively.
A picture
is worth a thousand words!
Each of the separate areas are able to
communicate with every device that uses the same routing protocol, but the
terminal in the OSPF area cannot communicate with the non-OSPF devices. The
primary task is to configure the network so that any device on the network is
able to telnet to any interface on any of the routers.
Checking the
routing table on routerC shows that only EIGRP routes are being advertised to
it.
routerC#sh ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is 172.16.4.1 to network 0.0.0.0
172.16.0.0/16 is variably subnetted, 4 subnets, 2 masks
C 172.16.4.0/24 is directly connected, Ethernet0
D 172.16.0.0/16 is a summary, 00:29:05, Null0
D 172.16.2.0/24 [90/2195456] via 172.16.4.1, 00:29:11, Ethernet0
D 172.16.3.0/24 [90/2221056] via 172.16.4.1, 00:12:45, Ethernet0
C 192.168.4.0/24 is directly connected, Loopback0
S* 0.0.0.0/0 [1/0] via 172.16.4.1
routerC# As you can see from the routing table, only directly
connected, static, and EIGRP routes are in the routing table on the router. To
configure redistribution, the first step is to select the boundary router. The
boundary router is the device that's at the edge of each routing protocol's
area. The obvious choice for this scenario is routerA. The pertinent starting
configuration information for routerA is:
!
interface Ethernet0
ip address 192.168.2.1 255.255.255.0
!
interface Ethernet1
ip address 172.16.3.1 255.255.255.0
!
interface Serial0
ip address 172.16.2.1 255.255.255.0
!
router eigrp 10
network 172.16.0.0 The second step for configuring redistribution is to
choose the core routing protocol, or the protocol that the other protocols will
redistribute into. Since all of the routers are Cisco devices, EIGRP makes the
most sense. With EIGRP being selected as the core protocols, RIP and OSPF will
be the edge protocols, or the protocols being redistributed (that gets step
three out of the way).
The next step is to get routerA to redistribute
RIP and OSPF into EIGRP. First configure routerA to be part of the OSPF area.
Use the commands:
routerA(config)# router ospf 1
routerA (config-router)# network 172.16.0.0 0.0.255.255 area 0
routerA (config-router)# exit Then you have to configure the EIGRP
instance to redistribute the OSPF.
routerA(config)# router eigrp 10
routerA (config-router)# redistribute ospf 1 When a routing protocol is
redistributed into EIGRP, it is necessary to configure the EIGRP metrics that
will be applied to the redistributed routes. The metric information could be
added to the end of the redistribute ospf command, but since RIP is being
redistributed as well, configuring a seed metric using the default-metric
command can be used:
routerA (config-router)# default-metric 10000 100 255 1 1500Where
10000 = Bandwidth, 100 = Delay, 255 = Reliability, 1 = Loading, and 1500 =
Maximum Transmission Unit, which will be used for both RIP and OSPF
redistributed routes. The routing table on routerC can be checked to see if
redistribution is working:
routerC#sh ip route
.
.
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 172.16.4.0/24 is directly connected, Ethernet0
D EX 172.16.5.0/24 [170/2221056] via 172.16.4.1, 00:01:29, Ethernet0
D 172.16.0.0/16 is a summary, 15:28:12, Null0
D 172.16.2.0/24 [90/2195456] via 172.16.4.1, 15:28:18, Ethernet0
D 172.16.3.0/24 [90/2221056] via 172.16.4.1, 14:31:34, Ethernet0
10.0.0.0/16 is subnetted, 1 subnets
D EX 10.10.0.0 [170/2221056] via 172.16.4.1, 00:01:29, Ethernet0
C 192.168.4.0/24 is directly connected, Loopback0
S* 0.0.0.0/0 [1/0] via...
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