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BjornCMVAS
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CORE Routers intermittently losing OSPF neighbours

Mon Apr 12, 2021 12:57 pm

Hi everyone, recently we have had some issues of OSPF sessions losing neighbors on some of our CORE routers.

Symptoms

Sometimes all OSPF sessions are affected one at a time. Reboot can seem to clear the issue but i think its just relieving symptoms and not resolving the actual cause. Sometimes only some OSPF sessions are affect, in the most recent incident last week only 1 OSPF was affected and none others.

Equipment
2 x CCR1036, version 6.46.8 and 6.45.7 respectively.

There are some things that I am already aware that should not be on out core, fixed, updated and/or removed when required.
* OSPF backbone too large - +-3700 routes on backbone
* NAT on Edge/CORE - There is NAT for some specific functions, this is planned to be removed and have connection tracking disabled.
* Firewalling before CORE to filter out unnecessary traffic like attacks/DDoS

Some other items we are already doing
* Updating the routers to the latest long-term release when possible.

Are there any other things to consider or be aware of beside the items above?
 
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StubArea51
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Re: CORE Routers intermittently losing OSPF neighbours

Mon Apr 12, 2021 2:10 pm

The very first thing I would do is get both CCRs upgraded to the same version using the long term version of RouterOS and see if the behavior continues. Using a different version of RouterOS on each OSPF neighbor will sometimes result in instability due to unintended interop issues between versions of code.

As an example, here are the OSPF bugs that have been fixed since the oldest version you're running has been released.
Release 6.47.6
*) ospf - optimized LSA printing for smaller message sizes;

Release 6.47.3
*) ospf - fixed disappearing NSSA default route;
*) ospf - fixed processing of "unknown" LSA type;

Release 6.47.2
*) ospf - fixed case when changing one distribution metric changed metrics for other distribution options;


Release 6.47.1
*) ospf - improved route tag processing for OSPFv3;

The current version for long term - 6.47.9 - has been incredibly stable with OSPF (and BGP/LDP/MPLS) for a lot of client networks that we work on.

Here is a presentation I did on OSPF troubleshooting that may help as well.

https://mum.mikrotik.com/presentations/ ... 892575.pdf

Also if you're running that many routes in your OSPF table, I'd strongly consider moving to iBGP with OSPF for loopbacks/ptp subnets
 
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BjornCMVAS
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Re: CORE Routers intermittently losing OSPF neighbours

Mon Apr 12, 2021 3:12 pm

Hi Kevin thanks so much will give the new long-term a go. We have also been in touch with IPA in 2019 with regards to some support, i have taken this route up again to hopefully assist in providing advise once the actual network is seen.
 
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StubArea51
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Re: CORE Routers intermittently losing OSPF neighbours

Mon Apr 12, 2021 4:47 pm

Cool...let us know how the testing goes with the new code!

Our EU team has grown a lot since 2019 and we now have multiple engineers across western and eastern Europe that also help to cover time zones in Africa since they overlap a good bit. Just give us a shout if you need some help :)

https://iparchitechs.com/contact

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