From: Niche (jackyliu419@gmail.com)
Date: Wed Oct 05 2005 - 23:20:20 GMT-3
Hi there,
How is the ospf-area arrangement? Any ospf network layout can brief us abit?
It's very hard (for me) to trace the possible problem source without this
kind of information, althought I know most of the time it's confidental but
every little bit help.
Cheers~
Jacky
On 10/6/05, Andrew Lissitz (alissitz) <alissitz@cisco.com> wrote:
>
> Hey Mike and group,
>
> Certainly sounds like you have your hands full Mike. Is everything ok
> now?
>
> During the routing loop, two (or more) routers thought they had the
> correct path to a destination. These two routers were not in sync, and
> they were told either dynamically or statically to route the way they
> did. Were these directly connected or did you see the packets bounce a
> couple of hops back and forth?
>
> If you think the flapping and SPF calculations caused this, then you
> have a big issue to work on. Your network should not go crazy with a
> flapping link...
>
> Without getting into a million options, design considerations, and
> choices ... You may consider your design and how a flapping link in one
> part of your network caused routing loops. If @ all possible, recreate
> your network in a lab and try and simulate what occurred today. You can
> buy software for your lab to simulate large scale OSPF and BGP routes.
>
> Have you considered a route optimization software? Perhaps an eval copy
> may even help. I think route science is a popular one... GS Group - is
> there a good route software to recommend here?
>
> Kindest regards Mike and good luck,
>
> Andrew
>
> -----Original Message-----
> From: Mike O [mailto:mikeeo@email.msn.com]
> Sent: Wednesday, October 05, 2005 7:39 PM
> To: Andrew Lissitz (alissitz)
> Cc: ccielab@groupstudy.com
> Subject: Re: OSPF routing loop
>
> Well I think the flapping link was causing OSPF to re-calaculate and I
> checked the log again and it looks like it was flapping every 5 seconds.
> I also should mentioned this network has about 180,000 nodes.
>
> ----- Original Message -----
> From: "Andrew Lissitz (alissitz)" <alissitz@cisco.com>
> To: "Mike O" <mikeeo@msn.com>; <mandingo2073@yahoo.com>
> Cc: <ccielab@groupstudy.com>
> Sent: Wednesday, October 05, 2005 4:30 PM
> Subject: RE: OSPF routing loop
>
>
> > Hello,
> >
> > Multicast would have problems if the Unicast table is not right. RPFs
> > etc... Incoming and outgoing interface problems...
> >
> > The reason I asked about redist is because OSPF, by itself, is pretty
> > good about keeping loops from occurring. If you saw packets expiring
> > and looping, then I would check your routing sources. Loops occur
> when
> > routing data is not consistent / correct and up to date.
> >
> > The devices that bounced the packets around thought they had the
> correct
> > route for the destinations. Why and where did they learn their
> routing
> > information....
> >
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Mike O
> > Sent: Wednesday, October 05, 2005 3:38 PM
> > To: mandingo2073@yahoo.com
> > Cc: ccielab@groupstudy.com
> > Subject: Re: OSPF routing loop
> >
> > Well we run mulitcast and it reported a unicast routing loop and when
> > you did a traceroute it kept bouncing back till the TTL expired.
> >
> >
> >>From: Carl Willias <mandingo2073@yahoo.com>
> >>Reply-To: Carl Willias <mandingo2073@yahoo.com>
> >>To: Mike O <mikeeo@msn.com>, alissitz@cisco.com,
> ccielab@groupstudy.com
> >>Subject: Re: OSPF routing loop
> >>Date: Wed, 5 Oct 2005 12:29:21 -0700 (PDT)
> >>
> >>Why do you think it was a routing loop? I have seen issues with a
> > flood of
> >>LSA's causing high CPU utilization on routers causing it to drop
> > packets,
> >>routing and otherwise.
> >>
> >>----- Original Message ----
> >>From: Mike O <mikeeo@msn.com>
> >>To: alissitz@cisco.com; ccielab@groupstudy.com
> >>Sent: Wednesday, October 05, 2005 1:59:30 PM
> >>Subject: RE: OSPF routing loop
> >>
> >>
> >>Yes we redistbute OSPF into BGP for iBGP.
> >>
> >>We also use the command "timers throttle spf 400 400 4000" and I think
> > it
> >>was trying to flood out LSA's while the link was flapping and caused a
> > loop
> >>in the Area
> >>
> >>
> >> >From: "Andrew Lissitz (alissitz)" <alissitz@cisco.com>
> >> >Reply-To: "Andrew Lissitz (alissitz)" <alissitz@cisco.com>
> >> >To: "Mike O" <mikeeo@msn.com>, <ccielab@groupstudy.com>
> >> >Subject: RE: OSPF routing loop
> >> >Date: Wed, 5 Oct 2005 14:34:22 -0400
> >> >
> >> >Mike, are you all performing any redistribution?
> >> >
> >> >
> >> >-----Original Message-----
> >> >From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of
> >> >Mike O
> >> >Sent: Wednesday, October 05, 2005 12:09 PM
> >> >To: ccielab@groupstudy.com
> >> >Subject: OSPF routing loop
> >> >
> >> >Can a rapidly flapping interface cause a routing loop with OSPF?
> >> >yesterday we had an interface bounce every 90 seconds and caused a
> >> >routing loop within the network until we shut it down. Shouldn't the
> >> >hold-down timers prevent this?
> >> >
> >> >
> >> >Thanks,
> >> >
> >> >Mike
> >> >
> >>
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