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New Member

BGP receive route problem for Transit customer

Hi,

I am working in an ISP which is one of the biggest ISP in my country. Currently my company is an ISP as well as IIG. In our ISP we have thousand of customer and in our IIG there are many ISP are connected with us. In the recent time I have faced a problem for the customer who have their own IPv4 resources and they are connected with us through our ISP network. Please see the below network diagram:

 

 customer router ---> ISP Core Router ---> IIG Aggregation Router ---> IIG Core Router 

 

Customer has their own IP resources which is 162.44.232.0/24 and we have configured eBGP multihop BGP with customer router to ISP core router as the customer is not directly connected with ISP core router. Now the problem is prefix which I am receiving from customer in ISP core router is best and valid but in IIG Aggregation Router customer prefix is only valid not best. As a result our IIG Core router not receving that prefix from IIG Aggregation Router and globally customer prefix is not reachable through us. Please see the below BGP receive route for your kind reference:

 

BGP receive route from ISP Core Router

>sh ip bgp neighbors 182.160.109.26 ro
BGP table version is 1346629, local router ID is 202.74.247.248
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path
 *>  162.44.232.0/24  182.160.109.26           0             0 58917 i

 

BGP receive route from  IIG Aggregation Router

#sh ip bgp neighbors 103.9.113.2 ro

BGP table version is 414210727, local router ID is 103.9.112.10
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, 
              r RIB-failure, S Stale, m multipath, b backup-path, f RT-Filter, 
              x best-external, a additional-path, c RIB-compressed, 
Origin codes: i - IGP, e - EGP, ? - incomplete
RPKI validation codes: V valid, I invalid, N Not found

     Network          Next Hop            Metric LocPrf Weight Path

 *   162.44.232.0/24  103.9.113.2                            0 24323 58917 i

Regards,

Shuvo

 

  • WAN Routing and Switching
7 REPLIES
Bronze

Hi,There are a few reasons

Hi,

There are a few reasons why this prefix may not be installed into the router:

 

It may be that the next hop used to reach the router is unreachable - can you verify that this not the case?

Do you have any route-maps applied to the peer from whom you are learning the prefix?

 

Best wishes

 

Mike

New Member

Hello lucymike, Thanks for

Hello lucymike,

 

Thanks for your reply. 

Next hop is reachable from IIG aggregation router and here is ping reply from IIG aggregation router :

Aggre-1#ping 182.160.109.26 source 103.9.113.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 182.160.109.26, timeout is 2 seconds:
Packet sent with a source address of 103.9.113.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

 

No route-map applied to thr peer from where I am learning the prefix.

 

New Member

Please post "sh ip bgp 162.44

Please post "sh ip bgp 162.44.232.0/24" from IIG Core as it is beign advertised by IIG Agg to the IIG core, it's just not best. That show output from IIG core does not help unless I have it backwards somehow.

the next-hop may not be reachable form the IIG core, and you performed a ping test from IIG Agg which has not issues as per you outputs.

 

Thanks

New Member

Hi Shuvo,

Hi Shuvo,

 

Can you post the output of the below two commands from the IIG Aggregation Router

sh ip bgp 162.44.232.0

sh ip route 162.44.232.0

 

Regards

Umesh

New Member

Hi Umesh, Please find the

Hi Umesh,

 

Please find the below output of command that you have asked:

 

#sh ip bgp 162.44.232.0
BGP routing table entry for 162.44.232.0/24, version 417080454
Paths: (4 available, best #3, table default)
  Advertised to update-groups:
     2291       3542      
  Refresh Epoch 1
  4788 58717 9230 58917 58917 58917 58917, (received & used)
    103.9.112.9 (metric 2) from 103.9.112.9 (103.9.112.9)
      Origin IGP, metric 100, localpref 270, valid, internal
      Community: 219938896 313786668 313786688 313787179
  Refresh Epoch 1
  58800 65110 24323 58917, (received-only)
    103.9.112.86 from 103.9.112.86 (103.245.108.33)
      Origin IGP, localpref 100, valid, external
  Refresh Epoch 2
  9498 58717 9230 58917 58917 58917 58917, (received & used)
    103.9.112.8 (metric 2) from 103.9.112.8 (103.9.112.8)
      Origin IGP, metric 0, localpref 270, valid, internal, best
  Refresh Epoch 1
  24323 58917, (received & used)
    103.9.113.2 from 103.9.113.2 (202.74.247.255)
      Origin IGP, localpref 100, valid, external

#sh ip route 162.44.232.0
Routing entry for 162.44.232.0/24
  Known via "bgp 58601", distance 200, metric 0
  Tag 9498, type internal
  Last update from 103.9.112.8 23:22:13 ago
  Routing Descriptor Blocks:
  * 103.9.112.8, from 103.9.112.8, 23:22:13 ago
      Route metric is 0, traffic share count is 1
      AS Hops 7
      Route tag 9498
      MPLS label: none
 

Hi Shuvo,from what I see,

Hi Shuvo,

from what I see, your customer is dual homed and the prefixes learned through AS 9498 have a higher local preference (270) within your AS than the prefix learned through AS 24323  (default: 100).

This may or may not be desired (I suppose it's not); I would recommend to ask an experienced colleague to assist you with that.

HTH

Rolf

New Member

 Hi Shuvo, The best route on

 

Hi Shuvo,

 

The best route on IIG Aggregation router is received via an IBGP neighbor. If the BGP peering IIG Aggregation and IIG Core is iBGP this route will not be sent to the IIG Core , thats the BGP Split Horiozon rule. 

And Like Rolf said , to get this traffic engineering done you should contact some of your senior colleagues, as its quite tough to suggest changes on your production network which could be quite complex.  

 

Regards

Umesh Shetty

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