Delete specific BGP community?

ferrets · Thu Aug 24, 2023 6:28 pm

Hi, I've just joined DN42 and start learning BGP. When I tried to play around with the BGP community, I've noticed that deleteing specific BGP community is not working the correct way.

Here is the connection:

R1---ebgp---R2---ibgp---R3

And this is a route received at R3

Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, i - is-is, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, g - slaac, y - bgp-mpls-vpn;
H - hw-offloaded; + - ecmp, B - blackhole
  b   afi=ip4 contribution=candidate dst-address=172.20.43.160/27 routing-table=dn42 gateway=10.172.0.2@dn42 immediate-gw=10.172.0.2%dn42.us.chr
       distance=200 scope=40 target-scope=30 belongs-to="bgp-IP-10.172.0.2@*2"
       bgp.peer-cache-id=*280171D .as-path="4242423914,4242420402" .communities=64511:2,64511:25,64511:34,64511:41,64511:1276
       .large-communities=4242423914:100:41 .local-pref=100 .med=0 .atomic-aggregate=yes .origin=igp
       debug.fwp-ptr=0x202C3840

before deleting any BGP community, the route has communites "64511:2,64511:25,64511:34,64511:41,64511:1276", and I want to remove some of them, so I created a community-list.

/routing filter community-list
add communities="64511:1,64511:2,64511:3,64511:4,64511:5,64511:6,64511:7,64511:8,64511:9,64511:21,64511:22,64511:23,64511:24,64511:25,64511:26,64511:27\
    ,64511:28,64511:29,64511:31,64511:32,64511:33,64511:34" disabled=no list=dn42_connection_info
/routing filter rule
add chain=ibgp disabled=no rule=" delete bgp-communities dn42_connection_info; accept;"

But when I set iBGP connection to use ibgp filter on R3, the communities had changed:

Flags: X - disabled, F - filtered, U - unreachable, A - active;
c - connect, s - static, r - rip, b - bgp, o - ospf, i - is-is, d - dhcp, v - vpn, m - modem, a - ldp-address, l - ldp-mapping, g - slaac, y - bgp-mpls-vpn;
H - hw-offloaded; + - ecmp, B - blackhole
  b   afi=ip4 contribution=candidate dst-address=172.20.43.160/27 routing-table=dn42 gateway=10.172.0.2@dn42 immediate-gw=10.172.0.2%dn42.us.chr
       distance=200 scope=40 target-scope=30 belongs-to="bgp-IP-10.172.0.2@*2"
       bgp.peer-cache-id=*280171D .as-path="4242423914,4242420402" .communities=64511:2,64511:25,64511:34 .large-communities=4242423914:100:41
       .local-pref=100 .med=0 .atomic-aggregate=yes .origin=igp
       debug.fwp-ptr=0x202C3840

It has communities 64511:2,64511:25,64511:34

communities in the "dn42_connection_info" list are not deleted, but other communities are deleted instead, only communities in the "dn42_connection_info" list remained.

swoga · Mon Sep 11, 2023 6:09 pm

Hello,

deleting and filtering on BGP communities is currently broken...
"delete bgp-communities ..." and "filter bgp-communities ..." are currently inverted when a community list used or the community is specified inline.
On the other hand, if a regex is used, the community is always deleted regardless if delete or filter.
I reported it to support in March (SUP-110901) but never got any response.
The problem still exists on the current release and I was surprised that no one else has noticed it.

Delete specific BGP community?

Delete specific BGP community?

Re: Delete specific BGP community?

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