[c-nsp] Extended Route Target Community Bug - Solved!

[Mark Tinka]

So I eventually figured this out... for the router to apply the extended 
community on inbound routes, one has to configure the export RT in the 
VRF itself.

Originally, I had used only import and export maps, without defining the 
RT explicitly in the VRF.

Turns out that even if you use import and export maps for fine-grained 
community management, you still need to define the RT in the VRF. That 
sort of acts like a "first step" in telling the router what communities 
to allow, and then the import/export maps are the "second step" in 
further being granular about what communities are allowed into and out 
of the VRF.

This documentation is nowhere in the wild that I could find, but hope it 
helps someone else that runs into the issue.

This is different from how Junos does it, where import/export maps can 
be used without having to explicitly define the RT in the VRF.

Mark.

On 9/21/23 14:27, Mark Tinka wrote:
> Hi all.
>
> I have a simple inbound route-map on a VPNv4 PE-CE BGP session that 
> does the below:
>
> route-map TEST deny 10
>  match rpki invalid
> !
> route-map TEST permit 20
>  match ip address prefix-list test-in
>  set metric 0
>  set local-preference 120
>  set extcommunity rt 65200:5
> !
> route-map TEST deny 65535
>
> The outcome of that policy works correctly for setting MED to 0 and 
> LOCAL_PREF to 120.
>
> However, I can't get it to set the extended RT community value to 
> 65200:5. Nothing happens.
>
> If I update that sequence with the below...
>
> route-map TEST permit 20
>  match ip address prefix-list test-in
>  set metric 0
>  set local-preference 120
>  set community 65200:5
>  set extcommunity rt 65200:5
>
> ... the regular community value is applied to the route. Of course, 
> this does not work for me since I need the extended RT community 
> applied to the route for it work further down the core.
>
> Am I doing something wrong, or is this a bug?
>
> System is an ASR1002-X running IOS XE 17.03.04a.
>
> For completeness, doing this on Junos works flawlessly.
>
> All help appreciated. Thanks.
>
> Mark.