[c-nsp] BGP Hold Time Expired, but why?
Christian Koch
christian at broknrobot.com
Tue Jul 22 08:35:31 EDT 2008
nothing out of the norm, i will try in a few minutes to take the link down
and snap a view though
thanks
On Tue, Jul 22, 2008 at 8:06 AM, Ozgur Guler <gulerozgur at yahoo.co.uk> wrote:
> When you do "show ip bgp nei detail" while the sessions are flapping,
> Do you see anything wrong in the TCP parameters?
> I remember a bug in 12.0S where TCP window size becomes 0 for BGP causing
> it to flap. Or if it is an MTU problem you might see that the BGP Keepalives
> are being throttled.
>
> --- On *Tue, 22/7/08, Christian Koch <christian at broknrobot.com>* wrote:
>
> From: Christian Koch <christian at broknrobot.com>
> Subject: Re: [c-nsp] BGP Hold Time Expired, but why?
> To: "Ozgur Guler" <gulerozgur at yahoo.co.uk>
> Cc: "Oliver Boehmer (oboehmer)" <oboehmer at cisco.com>, "cisco-nsp" <
> cisco-nsp at puck.nether.net>
> Date: Tuesday, 22 July, 2008, 12:54 PM
>
>
> they are all 7609-S
>
> On Tue, Jul 22, 2008 at 5:25 AM, Ozgur Guler <gulerozgur at yahoo.co.uk>
> wrote:
>
>> Is this a GSR?
>>
>>
>>
>> --- On *Tue, 22/7/08, Christian Koch <christian at broknrobot.com>* wrote:
>>
>> From: Christian Koch <christian at broknrobot.com>
>> Subject: Re: [c-nsp] BGP Hold Time Expired, but why?
>> To: "Oliver Boehmer (oboehmer)" <oboehmer at cisco.com>
>> Cc: "cisco-nsp" <cisco-nsp at puck.nether.net>
>> Date: Tuesday, 22 July, 2008, 1:58 AM
>>
>>
>> same issue, no differences...got me
>>
>>
>>
>>
>>
>> On Sun, Jul 20, 2008 at 2:53 AM, Oliver Boehmer (oboehmer) <
>> oboehmer at cisco.com> wrote:
>>
>> > I don't know, but I would try it.. Looks weird..
>>
>> >
>> > oli
>> >
>> > ------------------------------
>> > *From:* Christian Koch [mailto:christian at broknrobot.com]
>> > *Sent:*
>> Saturday, July 19, 2008 7:07 PM
>> >
>> > *To:* Oliver Boehmer (oboehmer)
>> > *Cc:* cisco-nsp
>> > *Subject:* Re: [c-nsp] BGP Hold Time Expired, but why?
>> >
>> > 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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>>
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>>
>>
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