[c-nsp] BGP Hold Time Expired, but why?
Christian Koch
christian at broknrobot.com
Sat Jul 19 13:06:43 EDT 2008
config look ok as far as i can see, i actually dont have bgp router-id set
in the bgp config... you think if i add that with the loopback ip, it would
make a difference?
config
router bgp 65000
no synchronization
bgp log-neighbor-changes
bgp graceful-restart restart-time 120
bgp graceful-restart stalepath-time 360
bgp graceful-restart
bgp dampening
neighbor Backbone peer-group
neighbor Backbone remote-as 65000
neighbor Backbone update-source Loopback1
neighbor Backbone version 4
neighbor Backbone send-community
neighbor 10.10.10.2 peer-group Backbone
neighbor 10.10.10.3 peer-group Backbone
no auto-summary
On Sat, Jul 19, 2008 at 12:29 PM, Oliver Boehmer (oboehmer) <
oboehmer at cisco.com> wrote:
> Hmm, "%BGP-5-ADJCHANGE: neighbor 10.10.10.3 Down BGP protocol
> initialization" looks unexpected, not sure what's happening..
> just a hunch, but can you double-check your config regarding loopback
> addresses, bgp router-id and things? Possibly add some bgp debug (deb
> bgp all events, deb bgp all, deb bgp all keep) and see if something
> weird pops up?
> What does the neighbor's (10.10.10.3) log say?
>
> oli
>
> ________________________________
>
> From: Christian Koch [mailto:christian at broknrobot.com]
> Sent: Saturday, July 19, 2008 3:08 PM
> To: Oliver Boehmer (oboehmer)
> Cc: cisco-nsp
> Subject: Re: [c-nsp] BGP Hold Time Expired, but why?
>
>
> hmm, i didnt check cef/mpls on the new path, i should try that.. there
> is connectivity between the loopbacks
>
> the session comes back up right after the timer expires.thats what
> puzzles me
>
> actually 3-4 is about how long i kept it down for..
>
>
> Jul 16 14:29:22 EDT: %LINK-3-UPDOWN: Interface TenGigabitEthernet2/2,
> changed state to down
> Jul 16 14:29:22 EDT: %LINEPROTO-SP-5-UPDOWN: Line protocol on Interface
> TenGigabitEthernet2/2, changed state to down
> Jul 16 14:29:22 EDT: %OSPF-5-ADJCHG: Process 10, Nbr 10.10.10.2 on
> TenGigabitEthernet2/2 from FULL to DOWN, Neighbor Down: Interface down
> or detached
> Jul 16 14:29:22 EDT: %LDP-5-NBRCHG: LDP Neighbor 10.10.10.2:0 (11) is
> DOWN (Interface not operational)
> Jul 16 14:29:22 EDT: %LINK-SP-3-UPDOWN: Interface TenGigabitEthernet2/2,
> changed state to down
> Jul 16 14:29:23 EDT: %LINK-SP-3-UPDOWN: Interface TenGigabitEthernet2/2,
> changed state to up
> Jul 16 14:29:23 EDT: %LINK-3-UPDOWN: Interface TenGigabitEthernet2/2,
> changed state to up
> Jul 16 14:29:23 EDT: %LINEPROTO-5-UPDOWN: Line protocol on Interface
> TenGigabitEthernet2/2, changed state to up
> Jul 16 14:29:23 EDT: %LINEPROTO-SP-5-UPDOWN: Line protocol on Interface
> TenGigabitEthernet2/2, changed state to up
> Jul 16 14:29:33 EDT: %LDP-5-NBRCHG: LDP Neighbor 10.10.10.2:0 (11) is UP
> Jul 16 14:30:19 EDT: %OSPF-5-ADJCHG: Process 10, Nbr 10.10.10.2 on
> TenGigabitEthernet2/2 from LOADING to FULL, Loading Done
> Jul 16 14:30:37 EDT: %LDP-5-NBRCHG: LDP Neighbor 10.10.10.2:0 (4) is
> DOWN (Discovery Hello Hold Timer expired)
> Jul 16 14:31:39 EDT: %LDP-5-NBRCHG: LDP Neighbor 10.10.10.2:0 (4) is UP
> Jul 16 14:32:38 EDT: %BGP-3-NOTIFICATION: received from neighbor
> 10.10.10.3 4/0 (hold time expired) 0 bytes
> Jul 16 14:32:38 EDT: %BGP-5-ADJCHANGE: neighbor 10.10.10.3 Down BGP
> protocol initialization
> Jul 16 14:32:45 EDT: %BGP-5-ADJCHANGE: neighbor 10.10.10.3 Up
>
>
>
> On Sat, Jul 19, 2008 at 3:24 AM, Oliver Boehmer (oboehmer)
> <oboehmer at cisco.com> wrote:
>
>
> No clue what's happening.. I've seen issues in the past with TCP
> PMTUD
> when the path converges over a link with a different MTU (which
> is
> happening in your case), but as BGP will not send packets larger
> than
> 4k, this shouldn't be an issue here.
>
> How long did you take down the link before bringing it back up?
> I assume
> longer than 3 minutes? Have you checked CEF and MPLS along the
> new path?
> You have IP connectivity between the loopbacks aR1 and bR2? Does
> the
> session come back up eventually, or will it stay down?
>
> oli
>
> Christian Koch <> wrote on Saturday, July 19, 2008 8:38 AM:
>
>
> > sorry forgot to specify
> >
> > the bgp session from aR1 to bR2 is the session in question
> >
> > ck
> >
> > On Sat, Jul 19, 2008 at 2:21 AM, Christian Koch
> > <christian at broknrobot.com> wrote:
> >
> >> Hello -
> >>
> >> I have the following topology in lab, testing different
> failure
> >> scenarios. When i disconnect the link between aR1 and bR1,
> what
> >> would appear to be normal happens - ospf and ldp neighbor go
> down.
> >>
> >> When i re-connect the link between aR1 and bR1, the interface
> comes
> >> back up, osfp/ldp neighbor is re-established.
> >>
> >> 3minutes later, bgp holdtime expires , and all links are up..
> >>
> >> aR1-----------------bR1
> >>> |
> >>> |
> >>> |
> >>> | aR2-----------------bR2
> >>
> >>
> >> Some Notes
> >> - All Links 10GE
> >> - Full ibgp mesh
> >> - Peering is to loopbacks
> >> - OSPF as IGP
> >> - Loopbacks in OSPF
> >> - MPLS Enabled on Interfaces
> >>
> >>
> >> OSPF cost between aR1 and aR2 is 1
> >> OSPF cost between bR1 and bR2 is 1
> >> OSPF cost between aR1 and bR1 is 250
> >> OSPF cost betwen aR2 and bR2 is 500
> >>
> >> MTU 9216 between aR1 and aR2, aR1 and bR1, aR2 AND BR2
> >> MTU 9182 between bR1 and bR2
> >>
> >>
> >> IOS on aR1 and aR2 is 12.2.33.SRB2 - SUP720
> >> IOS on bR1 and bR2 is 12.33.SRC - RSP720
> >>
> >>
> >> i am stumped, any ideas would be helpful in trying to
> understand why
> >> the bgp session is going down due to expired hold time, when
> all
> >> links are up..
> >>
> >> thanks!
> >>
> >> ck
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
> > --
> > ^christian$
>
> > _______________________________________________
> > cisco-nsp mailing list cisco-nsp at puck.nether.net
> > https://puck.nether.net/mailman/listinfo/cisco-nsp
> > archive at http://puck.nether.net/pipermail/cisco-nsp/
>
>
>
>
>
> --
> ^christian$
>
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