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surfnet
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Joined: Wed Sep 01, 2004 6:38 pm

BGP Filter Set Routing Mark stops advertisement

Fri Sep 03, 2021 1:10 am

I have asked this before with no answers, Ill try again, maybe its a bug?
Im trying to Set Routing Mark in a BGP In Filter, whenever I enable the rule, it marks the packet, but stops advertising the route

chain=Melchin-In prefix=10.5.5.1 action=passthrough set-routing-mark="RE"

If the rule is disabled the routes are advertised

[admin@BearCreekBH] > /routing bgp advertisements pr where prefix="10.5.5.1/32"
PEER PREFIX NEXTHOP AS-PATH ORIGIN LOCAL-PREF
Redwo... 10.5.5.1/32 10.100.0.46 65515 igp
Braem... 10.5.5.1/32 10.100.0.49 65515 igp
MntRob 10.5.5.1/32 10.100.0.69 65515 igp

When I enable the rule, the route get marked , but it stops advertising.
[admin@BearCreekBH] > /routing bgp advertisements pr where prefix="10.5.5.1/32"
PEER PREFIX NEXTHOP AS-PATH ORIGIN LOCAL-PREF
[admin@BearCreekBH] >


[admin@BearCreekBH] > /ip route pr detail where routing-mark="RE"
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, b - bgp, o - ospf, m - mme, B - blackhole, U - unreachable, P - prohibit
0 ADb dst-address=10.5.5.1/32 gateway=10.100.0.66 gateway-status=10.100.0.66 reachable via ether3 distance=20 scope=40 target-scope=10 routing-mark=RE bgp-as-path="65515" bgp-origin=igp received-from=Melchin



How can I use a routing filter to correctly mark a route?
 
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Cha0s
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Re: BGP Filter Set Routing Mark stops advertisement

Mon Sep 06, 2021 10:50 am

It's my understanding that a BGP instance will announce only what's on the routing table that it's configured to work on.
By default that's the main routing table. So when you mark an incoming prefix to change its routing table, it never enters the main routing table and thus it doesn't get advertised on your other peers.

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