[c-nsp] BGP Hold Time Expired, but why?

[Christian Koch]

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
10.10.10.34/0 (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$
> > _______________________________________________
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>



-- 
^christian$