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victorsoares
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HELP - BGP dynamic route flickering

Fri Aug 24, 2018 5:03 pm

Hi everyone and sorry for the capital letters on the post, but I really don't know what to do now.

It's been two days since the dynamic route of one of my BGP connections appears and disappears constantly. I have a static route for this too, but still this is causing me some trouble, since this BGP announces some of my public IP's that I use for my ERP systems.

Since this problem started, I'm having some instability on my pings on those IP's.

Any idea of what might be the case? Here are my BGP-Peers configuration.
Flags: X - disabled, E - established 
 0 E name="BGP-NIP" instance=nip remote-address=200.220.***.*** remote-as=***** 
     tcp-md5-key="" nexthop-choice=default multihop=yes route-reflect=no 
     hold-time=3m ttl=default in-filter=ebgp_nip_v4_in 
     out-filter=ebgp_nip_v4_out address-families=ip 
     update-source=vlan_nip_ubatuba default-originate=never 
     remove-private-as=yes as-override=no passive=no use-bfd=no 

 1 E name="BGP-SUPERIMAGEM-V4" instance=superimagem 
     remote-address=186.237.***.*** remote-as=****** tcp-md5-key="" 
     nexthop-choice=force-self multihop=yes route-reflect=no hold-time=3m 
     ttl=default in-filter=ebgp_superimagem_v4_in 
     out-filter=ebgp_superimagem_v4_out address-families=ip 
     update-source=vlan_super_ubatuba default-originate=never 
     remove-private-as=yes as-override=no passive=no use-bfd=no 

 2 E name="BGP-INTERNO" instance=interno remote-address=172.16.200.1 remote-as=1 
     tcp-md5-key="" nexthop-choice=force-self multihop=yes route-reflect=no 
     hold-time=3m ttl=default in-filter=ibgp-mpv-in out-filter=ibgp-mpv-out 
     address-families=ip update-source=vlan_caragua default-originate=never 
     remove-private-as=no as-override=no passive=no use-bfd=no 

 3 X name="BGP-CARAGUA" instance=default remote-address=191.7.***.*** 
     remote-as=****** tcp-md5-key="" nexthop-choice=default multihop=no 
     route-reflect=no hold-time=3m ttl=default in-filter=ibgp-mpv-in 
     out-filter=ibgp-mpv-out address-families=ip default-originate=never 
     remove-private-as=no as-override=no passive=no use-bfd=no
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Vooray
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Re: HELP - BGP dynamic route flickering

Fri Aug 24, 2018 6:21 pm

Hey!

You use multihop for bgp - is route to peer address stable?
You use update source vlan_nip_ubatuba. Is it stable?
Do you have anything interensting in your logs?
 
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Re: HELP - BGP dynamic route flickering

Fri Aug 24, 2018 8:03 pm

Start a continuous ping to the peer address...do you see packet loss or bouncing of the peer?

Also start a packet capture on that peering and filter for BGP, that way you can review the BGP updates and messages between your router and the upstream peer to see if your router is signalling a withdraw for some reason.
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victorsoares
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Re: HELP - BGP dynamic route flickering

Fri Aug 24, 2018 8:21 pm

@Vooray

You use multihop for bgp - is route to peer address stable?
Yes, it's stable.

You use update source vlan_nip_ubatuba. Is it stable?
Yes, stable too.

Do you have anything interensting in your logs?
Yes!
 time=14:13:38 topics=route,bgp,debug,packet 
   message="    WithdrawnRoutes=0.0.0.0/0" 

 time=14:13:38 topics=route,debug,calc message="Begin calculation" 

 time=14:13:38 topics=route,debug,event message="Removed route" 

 time=14:13:38 topics=route,debug,event message="    state=CANDIDATE" 

 time=14:13:38 topics=route,debug,event message="    dst-prefix=0.0.0.0/0" 

 time=14:13:38 topics=route,debug,event message="    attributes" 

 time=14:13:38 topics=route,debug,event message="        protocol=BGP" 

 time=14:13:38 topics=route,debug,event message="        scope=40" 

 time=14:13:38 topics=route,debug,event message="        target-scope=30" 

 time=14:13:38 topics=route,debug,event 
   message="        next-hop= address=200.220.***.***" 

 time=14:13:38 topics=route,debug,event message="        weight=100" 

 time=14:13:38 topics=route,debug,event message="        origin-type=BGP" 

 time=14:13:38 topics=route,debug,event message="        origin-instance-id=4" 

 time=14:13:38 topics=route,debug,event 
   message="        bgp-peer-router-id=200.220.***.***" 

 time=14:13:38 topics=route,debug,event message="        bgp-peer-flags=8" 

 time=14:13:38 topics=route,debug,event 
   message="        bgp-router-id=200.220.***.***" 

 time=14:13:38 topics=route,debug,event message="        bgp-origin=IGP" 

 time=14:13:38 topics=route,debug,event message="        bgp-as-path=******" 

 time=14:13:38 topics=route,debug,event message="        bgp-as-path-len=1" 

 time=14:13:38 topics=route,debug,event 
   message="        bgp-nexthop=200.220.***.***" 

 time=14:13:38 topics=route,debug,event message="        bgp-med=20" 

 time=14:13:38 topics=route,debug,event message="        use-te-nexthop=yes" 

 time=14:13:38 topics=route,debug,calc message="Select route" 

 time=14:13:38 topics=route,debug,calc message="    dst-address=0.0.0.0/0" 

 time=14:13:38 topics=route,debug,calc message="    attributes" 

 time=14:13:38 topics=route,debug,calc message="        protocol=STATIC" 

 time=14:13:38 topics=route,debug,calc message="        distance=10" 

 time=14:13:38 topics=route,debug,calc message="        scope=40" 

 time=14:13:38 topics=route,debug,calc message="        target-scope=30" 

 time=14:13:38 topics=route,debug,calc 
   message="        next-hop= address=186.237.***.***" 

 time=14:13:38 topics=route,debug,calc message="        comment=" 

 time=14:13:38 topics=route,debug,calc message="        origin-type=STATIC" 

 time=14:13:38 topics=route,debug,calc message="End calculation"
@IPANetEngineer

Ping remains stable as long as I have all my peers enabled.

I also noticed constant updates received every second by BGP-NIP.
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Vooray
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Re: HELP - BGP dynamic route flickering

Fri Aug 24, 2018 10:13 pm

Did you ask remote site to check their bgp?
 
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mrz
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Re: HELP - BGP dynamic route flickering

Mon Aug 27, 2018 11:30 am

It appears to me that remote peer is sending withdraw and then route update, which is causing route to be removed and then readded. Try to verify this with packet sniffer.
 
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victorsoares
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Re: HELP - BGP dynamic route flickering  [SOLVED]

Mon Aug 27, 2018 4:54 pm

Still not sure of what was going on there, but today I re enabled the filter that gave me the dynamic route 0.0.0.0/0 and everything is working fine.

Link provider told me everything was good on their end, but I still think that they found something like redrawn error and fixed, and now they won't admit that.

I haven't done any other configurations since last post nor restarted the device or anything like it.

This is going to my list of 'strange things that happen on networks'.

Thanks again everyone for all the help, even tough I still don't know what caused this issue, since I'm not able to reproduce the problem and it seems that it 'self resolved', I'm tagging this post as solved.
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