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New Member

BGP on A9K: Filtering prefixes using Communities on iBGP

Hello,

We are trying to filter some prefixes to a iBGP connection but it doesn't work properly:

The rpl is like this:

community-set MID

  15525:8657

end-set

route-policy Deny_Community_MID

  if community matches-any MID then

    drop

  else

    pass

  endif

end-policy

!

This rpl only removes the community from the prefix, and the prefix always arrive on the iBGP neighbor, which it not what we intend to do ! What we intend to do is to filter out the prefix ...

On our research we find this which is absolutely different from the IOS behaviour ...

"




BGP community and extended-community filtering cannot be  configured for iBGP neighbors. Communities and extended-communities are  always sent to iBGP neighbors

"

on

http://www.cisco.com/en/US/partner/docs/routers/asr9000/software/asr9k_r4.0/routing/configuration/guide/rc40asr9k_chapter1.html#task_1211424

Is this true or are we seeing this the wrong way?

Thank you!

1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

BGP on A9K: Filtering prefixes using Communities on iBGP

Works for me too.

Seems to be a documentation issue coming back from 3.4 release.

/A

8 REPLIES
New Member

BGP on A9K: Filtering prefixes using Communities on iBGP

My mistake. The prefixes are actually being filter! Still i don´t understand what is meant on this sentence from the IOSXR configuration guide.

"

BGP community and extended-community filtering cannot be  configured for  iBGP neighbors. Communities and extended-communities are  always sent  to iBGP neighbors

"

Anyone understands this ?

Thanks!

Cisco Employee

BGP on A9K: Filtering prefixes using Communities on iBGP

Works for me too.

Seems to be a documentation issue coming back from 3.4 release.

/A

New Member

BGP on A9K: Filtering prefixes using Communities on iBGP

Thanks Akiritch. Is it possible to open a documentation bug to correct it ?

Cisco Employee

BGP on A9K: Filtering prefixes using Communities on iBGP

there is a feedback form at the bottom of the document. let's see if that works  (I am interested myself)

may you try?

/A

New Member

BGP on A9K: Filtering prefixes using Communities on iBGP

Done! But i have several more examples on the poor and buggy IOSXR documentation .. :

Command Reference A9K 4.0, BGP Chapter:

                The commands “additional-paths” should have a brief explanation stating that they belong the PIC Edge Framework .. but nothing .. No usage guidelines

Command Reference A9K 4.0, IS-IS Chapter:

The command “ipfrr” is deprecated and replaced by “fast-reroute” but still appears on documentation ..

Configuration Guide A9K 4.0, Routing Chapter:

                There is no reference to PIC anywhere .. only a couple of meaningless words

Cisco Employee

BGP on A9K: Filtering prefixes using Communities on iBGP

i'll check it.

/A

Cisco Employee

BGP on A9K: Filtering prefixes using Communities on iBGP

Hello,

we've opened following request to correct the documentation

CSCtx13654    Correct Routing CG and CR documentation based on feedback from XR Forum

regards,

/A

New Member

BGP on A9K: Filtering prefixes using Communities on iBGP

Hi Alexi,

                                May I know how to configure "IP address-specific extended community" (

BGP Extended Communities Attribute) in IOS XR ??

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