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Belyivulk
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BGP Loop when interface goes down

Sun Apr 04, 2010 3:29 am

Hey All,

Hoping someone out there can tell me where i'm going wrong with this....

ROS 4.6 on RB800 - using BGP to distribute routes on our network. Everything elsewhere on the network is working as expected, however on the RB800, when an interface drops / becomes unavailable even for a second we see all traffic destined for it loop over the ethernet interface to our edge (default gateway for the RB800).

How can we stop this from happening, and / or is there something we have missed? Config below..

0 name="default" as=65500 router-id=124.157.64.1 redistribute-connected=yes
redistribute-static=yes redistribute-rip=no redistribute-ospf=no
redistribute-other-bgp=yes out-filter=ThisInstance-Out
client-to-client-reflection=no ignore-as-path-len=no routing-table=""

0 E name="Primary(to edge)" instance=default remote-address=x.x.x.201
remote-as=65500 tcp-md5-key="" nexthop-choice=default multihop=no
route-reflect=no hold-time=5s ttl=1 in-filter=Primary(to edge)-In
out-filter=Primary(to edge)-Out address-families=ip
default-originate=never remove-private-as=no as-override=no passive=no
use-bfd=no

1 E name="Link-that-drops" instance=default remote-address=x.x.x.230
remote-as=65500 tcp-md5-key="" nexthop-choice=default multihop=no
route-reflect=yes hold-time=10s ttl=3 in-filter=Link-that-drops-In
out-filter=Link-that-drops-Out address-families=ip default-originate=never
remove-private-as=no as-override=no passive=no use-bfd=no

0 chain=Primary-In invert-match=no action=passthrough
set-in-nexthop=x.x.x.201

1 chain=Link-that-drops-In invert-match=no action=passthrough
set-in-nexthop=124.157.64.230

2 chain=Link-that-drops-In prefix=0.0.0.0/0 invert-match=no action=discard

Edit: I've also found that the loop occurs when i remove the 'set-in-nexthop' in the filter.
 
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Re: BGP Loop when interface goes down

Tue Apr 06, 2010 11:13 am

I've the same problem on RB1000 with ROS 4.6
 
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Chupaka
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Re: BGP Loop when interface goes down

Sat Apr 24, 2010 9:56 pm

what's strange if traffic goes to the default gateway? =)

you should either drop it in your firewall rules, or add 'unreachable' routes for networks, received via BGP...
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