250.15.0 255.255.255.252 IS SUBNETTED, 1 SUBNETSC 250.15.0 IS...

Question

203.250.15.0 255.255.255.252 is subnetted, 1 subnets

C 203.250.15.0 is directly connected, Serial0

O 203.250.14.0 [110/74] via 203.250.15.1, 02:50:46, Serial0

Well, it doesn't look like any of the BGP entries has made it to the

routing table. There are two problems here:

Problem 1:

The Nexthop for these entries 128.213.63.2 is unreachable. This is

true because we do not have a way to reach that nexthop via our

IGP (OSPF). RTB has not learned about 128.213.63.0 via OSPF. We can

run OSPF on RTA s0 and make it passive, and this way RTB would know

how to reach the nexthop 128.213.63.2. We could also change the

nexthop by using the bgp nexthopself command between RTA and RTB.

RTA's configs would be:

RTA#

hostname RTA

ip subnet-zero

interface Loopback0

ip address 203.250.13.41 255.255.255.0

interface Ethernet0

ip address 203.250.14.1 255.255.255.0

interface Serial0

ip address 128.213.63.1 255.255.255.252

router ospf 10

passive-interface Serial0

network 203.250.0.0 0.0.255.255 area 0

network 128.213.0.0 0.0.255.255 area 0

router bgp 100

network 203.250.0.0 mask 255.255.0.0

neighbor 128.213.63.2 remote-as 200

neighbor 203.250.15.2 remote-as 100

neighbor 203.250.15.2 update-source Loopback0

The new BGP table on RTB now looks like this:

RTB#sh ip bgp

BGP table version is 10, local router ID is 203.250.15.2

Status codes: s suppressed, d damped, h history, * valid, > best,

i - internal Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*>i128.213.0.0 128.213.63.2 0 100 0 200 i

*>i192.208.10.0 128.213.63.2 100 0 200 400 500

300 i

*>i195.211.10.0 128.213.63.2 100 0 200 400 500 i

*>i200.200.10.0 128.213.63.2 100 0 200 400 i

RTB#sh ip rou

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP

D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area

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, * -

candidate default

Gateway of last resort is not set

Answer