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BGP community attribute configuration

  • 1 October 2020
  • 3 replies
  • 77 views

Hi,

I need to advertise BGP community strings to my ISP.

I am advertising several networks, and for each of these networks I need to send either 123:1 or 123:2 - where the ISP AS number is 123. This will then be used by the ISP to set a local preference on their end.

It seems that doing this is far more complicated with Extreme than with other vendors and involves writing a policy file.
I'm not clear if I'm sending an 'soo' or 'rt' attribute, or how to apply the community strings to specific networks that I'm advertising.

Please could someone give me an example config?:

Say I have the following configuration:

configure bgp AS-number 65432
configure bgp routerid 100.100.100.100
configure bgp add network 111.111.111.0/24
configure bgp add network 222.222.222.0/24

create bgp neighbor 123.123.123.123 remote-AS-number 123
enable bgp neighbor 123.123.123.123

I would like to send the community string 123:1 for the 111.111.111.0/24 network, and 123:2 for the other network.

(I am using X460 G2s, EXOS 30.7)

 

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Best answer by Christopher Thompson 2 October 2020, 13:04

Hi,

You can edit the community string with BGP export policy.  

It would most likely look something like this below and be applied via a bgp export policy:

entry ISPCommTest {
if match any {
nlri 111.111.111.0/24;
} then {

community add "123:1";
permit;
}
}

entry ISPCommTest2 {
if match any {
nlri 222.222.222.0/24;
} then {

community add "123:2";
permit;
}
}

 

 

Thanks,

Chris Thompson

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3 replies

Userlevel 3

Hi,

You can edit the community string with BGP export policy.  

It would most likely look something like this below and be applied via a bgp export policy:

entry ISPCommTest {
if match any {
nlri 111.111.111.0/24;
} then {

community add "123:1";
permit;
}
}

entry ISPCommTest2 {
if match any {
nlri 222.222.222.0/24;
} then {

community add "123:2";
permit;
}
}

 

 

Thanks,

Chris Thompson

Thank you for this @Christopher Thompson.

When you say ‘apply a bgp export policy’ - would the below command be correct in our example?

configure bgp neighbor 123.123.123.123 route-policy out ISPCommTest

Userlevel 3

Hi Jon,


I haven’t had a chance to test but that is the correct syntax regarding the BGP policy. 

 

Thanks,

Chris Thompson

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