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

Sat Jul 19 12:29:30 EDT 2008

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$

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-- 
^christian$ 