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kevinM
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OSPF-v3 interoperability with Arista

Sat May 09, 2020 12:22 am

We have an almost entirely Mikrotik routed network. We recently introduced an arista into our enviroment acting as an L3 router and imediatly found an issue regarding ospf-v3 adjacency. I then built a lab and was able to reproduce the issue with a strip down config. In this scenario once ospfv3 is establihed to the arista from mirkotik1, all subsequent OSPF-v3 sessions from mikrotik1 to neighboring mikrotik routers failed and got stuck in the execstart/2way state. If you disabled the ospfv3 session to the arista and restart the sessions to the neighbors mirkrotik routers, then the sessions come up and work normally.

So the issue appears to be, once adjancy is established from a mikrotik to the arista, after that all adjancies fail while the adjancies to the arista stays solid. I have tried multiple versions of mikrotik firmware including the latest bugfix 6.45.9. I have also tried multiple software version on the arista including the latest release of 4.24.0F. The issue presents itself in all configurations and it easily reproducable. i've engaged Arista support and it seems that because the adjancy to the arista is up and the only symptoms are off the mikrotik side, there is nothing they can do.

Wondering is anyone has any ideas of thoughts on how to move forward the troubleshooting process here...
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kevinM
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Re: OSPF-v3 interoperability with Arista

Sat May 09, 2020 8:37 am

through further troubleshooting i've been able to confirm the part of the arista config mikrotik doesn't see to like is when it advertises external type1/2 routes. If the arista is only advertising intra area routes the adjancies on the mikrotik all come up. But when the arista advertises a route lets say "default-information originate" for example, it advertises it via external type2 and the issue with mikrotik adjancies occures.
 
mmc
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Joined: Wed Dec 29, 2004 1:44 am

Re: OSPF-v3 interoperability with Arista

Mon May 25, 2020 7:21 am

ospfv3 in ros6 is just useless. when you try to run it on two different vlans on one physical link, it sends it's hello packets via the wrong vlan and each router becomes a DR fighting with each other than...
suggestion from mt support: known bug, wait for ros7 (since years now)
 
kevinM
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Re: OSPF-v3 interoperability with Arista

Tue May 26, 2020 2:12 am

Ya, I have a ticket open with mikrotik support and there looking into it. OSPFv3 for mikrotik seems be be very buggy in general, I've seen multiple issue interacting with it including with cisco. I'll see what support has to say about it, I wouldn't be surprised if it was a "wait for ros7" type of response... But i'm hopeful
 
kevinM
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Re: OSPF-v3 interoperability with Arista

Mon Jun 01, 2020 6:52 pm

Mikrotik support was very helpfull and identified the problem to be with how arista is tagging external routes with tag 0. Most platforms default behavoir is to send external routes with tag 0 but arista is apparently doing it a little different and it was freaking out mikrotik. They provided me a bugfix version where they fixed the issue and said the fix will be included in the 6.48 release train. But if anyone runs into this problem there is an easy work-a-round, the issue mikrotik has with the external routes apparently on pertains to tag 0, so if you change the default behavoir of the arista and have it send external routes with a tag=1 or anthing other then 0 using a routemap then the issue goes away.

Hopefully this will help someone else down the road that is trying to incorporate arista into their mikrotik network...

Kudos to Mikrotik support for helping us with this issue.

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