BGP lab help

Andy White · ‎10-02-2013

Hello,

I'm just testing my knowledge (or lack of) with this lab I'm doing, can anyone hint as to why I can't ping 4.4.4.4 from R1 eventhough it is valid and best?

R1

R1#sh run | s router

router bgp 100

no synchronization

bgp log-neighbor-changes

network 1.1.1.1 mask 255.255.255.255

neighbor 10.1.1.5 remote-as 500

neighbor 172.12.123.2 remote-as 100

neighbor 172.12.123.3 remote-as 300

no auto-summary

R1#

R1#sh ip bgp

BGP table version is 7, local router ID is 1.1.1.1

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

r RIB-failure, S Stale

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

Network Next Hop Metric LocPrf Weight Path

*> 1.1.1.1/32 0.0.0.0 0 32768 i

*>i2.2.2.2/32 172.12.123.2 0 100 0 i

*> 3.3.3.3/32 172.12.123.3 0 0 300 i

* i 172.12.123.2 0 100 0 300 i

* 4.4.4.4/32 172.12.123.3 0 300 400 i

*>i 172.12.123.2 0 100 0 400 i

*> 5.5.5.5/32 10.1.1.5 0 0 500 i

R1#

R2

R2#sh run | s router

router bgp 100

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

neighbor 172.12.123.1 remote-as 100

neighbor 172.12.123.1 next-hop-self

neighbor 172.12.234.3 remote-as 300

neighbor 172.12.234.4 remote-as 400

no auto-summary

R2#

R2#sh ip bgp

BGP table version is 5, local router ID is 2.2.2.2

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

r RIB-failure, S Stale

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

Network Next Hop Metric LocPrf Weight Path

*>i1.1.1.1/32 172.12.123.1 0 100 0 i

*> 2.2.2.2/32 0.0.0.0 0 32768 i

* i3.3.3.3/32 172.12.123.3 0 100 0 300 i

* 172.12.234.4 0 400 300 i

*> 172.12.234.3 0 0 300 i

* 4.4.4.4/32 172.12.234.3 0 300 400 i

*> 172.12.234.4 0 0 400 i

* i5.5.5.5/32 10.1.1.5 0 100 0 500 i

R2#

R3

R3#sh run | s router

router bgp 300

no synchronization

bgp log-neighbor-changes

network 3.3.3.3 mask 255.255.255.255

neighbor 172.12.34.4 remote-as 400

neighbor 172.12.123.1 remote-as 100

neighbor 172.12.123.2 remote-as 100

neighbor 172.12.234.2 remote-as 100

neighbor 172.12.234.4 remote-as 400

no auto-summary

R3#

R3#sh ip bgp

BGP table version is 6, local router ID is 3.3.3.3

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

r RIB-failure, S Stale

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

Network Next Hop Metric LocPrf Weight Path

* 1.1.1.1/32 172.12.234.2 0 400 100 i

* 172.12.34.4 0 400 100 i

* 172.12.234.2 0 100 i

*> 172.12.123.1 0 0 100 i

* 2.2.2.2/32 172.12.123.1 0 100 i

* 172.12.234.2 0 400 100 i

* 172.12.34.4 0 400 100 i

*> 172.12.234.2 0 0 100 i

*> 3.3.3.3/32 0.0.0.0 0 32768 i

* 4.4.4.4/32 172.12.123.1 0 100 400 i

* 172.12.234.4 0 100 400 i

* 172.12.234.4 0 0 400 i

*> 172.12.34.4 0 0 400 i

*> 5.5.5.5/32 172.12.123.1 0 100 500 i

R3#

R4

R4#sh run | s router

router bgp 400

no synchronization

bgp log-neighbor-changes

network 4.4.4.4 mask 255.255.255.255

neighbor 172.12.34.3 remote-as 300

neighbor 172.12.234.2 remote-as 100

neighbor 172.12.234.3 remote-as 300

no auto-summary

R4#

R4#sh ip bgp

BGP table version is 6, local router ID is 4.4.4.4

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

r RIB-failure, S Stale

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

Network Next Hop Metric LocPrf Weight Path

* 1.1.1.1/32 172.12.234.3 0 300 100 i

* 172.12.34.3 0 300 100 i

*> 172.12.234.2 0 100 i

* 2.2.2.2/32 172.12.234.3 0 300 100 i

* 172.12.34.3 0 300 100 i

*> 172.12.234.2 0 0 100 i

* 3.3.3.3/32 172.12.234.3 0 100 300 i

* 172.12.234.3 0 0 300 i

*> 172.12.34.3 0 0 300 i

*> 4.4.4.4/32 0.0.0.0 0 32768 i

* 5.5.5.5/32 172.12.234.3 0 300 100 500 i

*> 172.12.34.3 0 300 100 500 i

R4#

Karsten Iwen · ‎10-02-2013

How do you test it? Just with a "ping 4.4.4.4"?

I would assume that the ping reaches R4 (you can test that with "debug ip icmp" on R4), but if you don't specify the source of your ping as 1.1.1.1, then R4 can't answer the ping as R4 doesn't know how to reach 172.12.123.1

--
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http://www.kiva.org/invitedby/karsteni

Andy White · ‎10-02-2013

Doh, ping 4.4.4.4 source 1.1.1.1 worked.

To get R4 to ping 172.12.123.1 is it best to add a routing protocol over the top?

This is R4:

1.0.0.0/32 is subnetted, 1 subnets

B 1.1.1.1 [20/0] via 172.12.234.2, 01:41:15

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 172.12.234.2, 01:41:15

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [20/0] via 172.12.34.3, 01:41:15

4.0.0.0/32 is subnetted, 1 subnets

C 4.4.4.4 is directly connected, Loopback0

5.0.0.0/32 is subnetted, 1 subnets

B 5.5.5.5 [20/0] via 172.12.34.3, 01:41:15

172.12.0.0/16 is variably subnetted, 3 subnets, 2 masks

C 172.12.234.0/24 is directly connected, FastEthernet0/0

C 172.12.34.3/32 is directly connected, Serial0/0

C 172.12.34.0/24 is directly connected, Serial0/0

R4#

and R1

1.0.0.0/32 is subnetted, 1 subnets

C 1.1.1.1 is directly connected, Loopback0

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [200/0] via 172.12.123.2, 01:42:28

3.0.0.0/32 is subnetted, 1 subnets

B 3.3.3.3 [20/0] via 172.12.123.3, 01:42:22

4.0.0.0/32 is subnetted, 1 subnets

B 4.4.4.4 [200/0] via 172.12.123.2, 00:05:16

5.0.0.0/32 is subnetted, 1 subnets

B 5.5.5.5 [20/0] via 10.1.1.5, 01:42:30

172.12.0.0/24 is subnetted, 1 subnets

C 172.12.123.0 is directly connected, Serial0/0

10.0.0.0/24 is subnetted, 1 subnets

C 10.1.1.0 is directly connected, FastEthernet0/0

R1#

Karsten Iwen · ‎10-02-2013

R4 has to learn it through BGP as you don't want an IGP between your different AS. Tell your routers to also anounce the transfer-links.

--
Don't stop after you've improved your network! Improve the world by lending money to the working poor:
http://www.kiva.org/invitedby/karsteni

Andy White · ‎10-03-2013

I've not heard of transfer links, would you mind explaining this a little more and how I can configure?

Thanks

cadet alain · ‎10-03-2013

Hi,

transfer links means the links between your routers but usually you only advertsie your end host subnets not the links between your routers and to test it you specify the source address in your ping.

Regards

Alain

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