BGP help - missing something simple I know

Unanswered Question
Jul 2nd, 2009

I have a simple BGP lab set-up:

Rack and Topology

2950-A - MDF-Site A 10.252.1.3

3560-A - Edge-Site A 10.252.1.1

3560-B - Edge-Site A 10.252.1.2

2811-A - CE-Site A

2811-B - CE-Site A

2811-Carrier A - PE-Site A

2811-Carrier B - PE-Site B

2811-A - CE-Site B

2811-B - CE-Site B

3750 - Edge-Site B 10.252.2.1

3560 - Edge-Site B 10.252.2.2

2950 - MDF-Site B 10.252.2.3

I have iBGP running:

Site A

3560-A 10.252.1.1 to 2811-A 10.252.1.4 and 2811-B 10.252.1.5

Site B

3750 10.252.2.1 to 2811-A 10.252.2.4 and 2811-B 10.252.2.5

Then I also have eBGP running between:

Site A:

2811-A Loopback0 208.10.10.1 to 2811-Carrier Loopback0 123.1.1.1

and the scenerio continues.

Here are the configs for each device as it relates to BGP and routing:

Please see attached config.

Here is what I am trying to accomplish and it fails.

I just wanted to intiate a ping from my MDF to the test IP on the Carrier loopback100 (you will this reflected in the config)

However, I cannot ping this IP.

I can ping the serial IP on the 2811-A - CE-Site A but cannot ping the directly connected ip at the PE 2811-Carrier side.

From the CE-Site A router:

MONR001-A#ping 10.252.1.3

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.252.1.3, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

MONR001-A#ping 157.130.0.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 157.130.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms

MONR001-A#ping 210.1.1.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 210.1.1.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

210.1.1.1 is a loopback for testing in the carrier network.

10.252.1.3 is the MDF switch

MONMDF01-A#ping 157.130.0.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 157.130.0.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

MONMDF01-A#ping 157.130.0.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 157.130.0.1, timeout is 2 seconds:

.....

Success rate is 0 percent (0/5)

MONMDF01-A#traceroute 157.130.0.1

Type escape sequence to abort.

Tracing the route to 157.130.0.1

1 monr001-a (10.252.1.4) 4 msec 0 msec 0 msec

2 * * *

3 * * *

MONR001-A#sh ip route 0.0.0.0

Routing entry for 0.0.0.0/0, supernet

Known via "bgp 1000", distance 20, metric 0, candidate default path

Tag 209, type external

Last update from 123.1.1.1 00:32:46 ago

Routing Descriptor Blocks:

* 123.1.1.1, from 123.1.1.1, 00:32:46 ago

Route metric is 0, traffic share count is 1

AS Hops 1

Route tag 209

I have this problem too.
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Giuseppe Larosa Thu, 07/02/2009 - 12:36

Hello Rick,

the problem is on the return path

CarrierA knows only one subnet from site A

but MDF switch uses

10.252.1.3 is the MDF switch

for this reason you can ping the ce side of the serial link

but you cannot ping carrier side of the serial link and also you cannot ping the test loopback.

being a C2950 L2 only it has only one possible source IP address for its ICMP packets and it is not known at the carrier router

CARRIER-A#sh ip bgp neigh 208.10.10.1 ro

BGP table version is 2, local router ID is 210.1.1.1

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

*> 63.10.10.0/24 208.10.10.1 0 100 0 1000 i

Total number of prefixes 1

you have also a filter that allows it to accept only 63.10.10.0/24

Hope to help

Giuseppe

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