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BGP Troubleshooting

Hello All,

In our environment we are not using the AS number 701, but I'm not sure why I'm seeing the AS number 701 while tracing the path.

  1 10.97.61.53 [AS 701] 4 msec 0 msec 0 msec

  2 10.97.61.65 [AS 701] 4 msec 0 msec 0 msec

  3 10.30.2.105 [AS 701] 0 msec 0 msec 0 msec

  4  *  *  *

  5 152.185.36.53 [AS 701] [MPLS: Label 33225 Exp 0] 224 msec 240 msec 244 msec

  6 152.185.36.54 [AS 701] 220 msec 220 msec 220 msec

  7 10.30.40.82 [AS 701] 224 msec 220 msec 228 msec

  8 10.73.0.238 [AS 701] 224 msec -

    10.73.0.29 [AS 701] 224 msec

    10.73.0.238 [AS 701] 240 msec

  9 10.73.0.21 [AS 701] 232 msec

    10.73.0.33 [AS 701] 228 msec 224 msec

10 10.73.191.82 [AS 701] 220 msec 220 msec 220 msec

11 10.73.191.38 [AS 701] 220 msec *  220 msec

Can any body help me to understand the AS number 701 in the path?

Regards,

Thiyagu

4 REPLIES 4
Highlighted
Hall of Fame Cisco Employee

BGP Troubleshooting

Hi Thiyagu,

Your router must somehow believe that the route belongs to AS 701... Can you execute the following command and post back the results?

show ip bgp 10.73.191.38 bestpath

Thanks!

Best regards,

Peter

Beginner

BGP Troubleshooting

Hi Rajan,

It can be a service provider issue.Is this link connected to verizon(AS701)....Please check above command given by peter that could help if routes are learned from verizon.

BRegards

Mukul

Highlighted

BGP Troubleshooting

Thanks all for your reply.

#show ip bgp 10.73.191.38

BGP routing table entry for 0.0.0.0/0, version 21

Paths: (2 available, best #2, table Default-IP-Routing-Table)

Multipath: eBGP iBGP

  Advertised to update-groups:

     2          3

  64681 65232 6523 65332 701, (received & used)

    10.97.159.253 (metric 2) from 10.97.159.253 (10.97.159.253)

      Origin IGP, metric 0, localpref 100, valid, internal

64681 65232 6523 65332 701, (received & used)

    10.97.61.53 from 10.97.61.53 (10.97.61.126)

      Origin IGP, localpref 100, valid, external, best

I'm seeing the AS number 701 in the path. I'm wondering for an Intranet subnet why public AS is comming?

Will there be any issue because of this ? If so how can I resolve that?

Regards,

Thiyagu

Highlighted
Cisco Employee

BGP Troubleshooting

Hi Thiyagu,

You will need to trace it back to the router originating the route as this router seems to be using AS701. The proper way to handle it would be to use a private AS number on the originating router.

Regards

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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