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BGP Auto Summary

hello all,

I have this situation :-

------rtr1---------------rtr2-------

rtr1 is an external customer, and rtr2 is our company router.

Not sure of the config of the customer router, but our router has automatic summarisation ENABLED.

Should this not mean that any route we receive from our customer should be at the class boundary (again, not sure if the customer is using redistribution into BGP of its routes or has network statements under BGP)

Please could someone please clarify this point as we are receiving routes that at not at the class boundary and are varibly subnetted.

Routing Protocol is "bgp 500"

Outgoing update filter list for all interfaces is not set

Incoming update filter list for all interfaces is not set

IGP synchronization is enabled

Automatic route summarization is enabled

Many thx indeed,

Ken

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

Re: BGP Auto Summary

BGP auto-summary will affect the way routes are redistributed or generated in BGP. It doesn't affect the routes you receive from your peer(s).

For instance, if you redistribute routes in BGP and that auto-summary routes is enabled, BGP will summarize the redistributed routes the major net boundary.

If you have a netwrok statement for any major network and auto-summary is enabled, BGP will originate this major net if any component (subnet) is present in the local RIB. If no auto-summary is configured then BGP will expect a perfect match between the network statement and the prefix in the local RIB.

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
1 REPLY
Cisco Employee

Re: BGP Auto Summary

BGP auto-summary will affect the way routes are redistributed or generated in BGP. It doesn't affect the routes you receive from your peer(s).

For instance, if you redistribute routes in BGP and that auto-summary routes is enabled, BGP will summarize the redistributed routes the major net boundary.

If you have a netwrok statement for any major network and auto-summary is enabled, BGP will originate this major net if any component (subnet) is present in the local RIB. If no auto-summary is configured then BGP will expect a perfect match between the network statement and the prefix in the local RIB.

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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