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ZeroByte
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OSPFv3 adjacency with Cisco routers

Thu Aug 29, 2019 11:01 pm

We primarily use Cisco on our network core, but are deploying a CCR1072-1G-8S+ as a PPPoE end-user concentration box. As such, it needs to speak OSPF with the rest of the core network.

The design is a fairly straightforward dual-uplink; each uplink network having two core routers as DR/BDR.
It's the same two core routers connected to both uplink networks.

Everything's fine on IPv4, but OSPFv3 is only forming adjacencies on one of the uplinks at a time. I think it's because we use custom link-local IPv6 addresses on our routers to make it easier to identify them in routing tables, etc.
The primary core router is fe80::1 on both sides, and the secondary core router is fe80::2 on both sides. Our Cisco access routers have no trouble with this, but the CCR is logging info-level messages as follows:
Discarding packet: no neighbor with this RouterId
RouterId=1.1.1.1
Source=fe80::1
Discarding packet: no neighbor with this RouterId
Routerid=2.2.2.2
Source=fe80::2
etc...

Both routers 1.1.1.1 and 2.2.2.2 are active in the neighbors table on the "A" uplink, but the "B" uplink shows no neighbors.
I've also been able to get them active on "B" with "A" refusing to establish adjacency.

The Cisco routers show the CCR as being stuck in state INIT/DROTHER (i.e. it never reaches 2WAY/DROTHER)

I suspect that the CCR is getting confused by the fact that the same router has the same routerID and same link-local address on both interfaces.

Is this the case?

p.s. It sure would be nice if I could manually assign fe80::809 as link-local addresses on the Mikrotik.... ;)
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you should not cling to your fork.
The soup will get cold.
 
mducharme
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Re: OSPFv3 adjacency with Cisco routers

Fri Aug 30, 2019 12:21 am

I suspect that the CCR is getting confused by the fact that the same router has the same routerID and same link-local address on both interfaces.

Is this the case?
Yes - MikroTik OSPFv3 currently uses the neighbor device's link local address as the sole unique identifier for the neighbor relationship (internal UID for neighbors table). Ideally, I think it should probably be changed to instead use a combination of the interface and the link local as a unique ID, since that should be guaranteed unique. With the current behavior (which I was told isn't going to be fixed until ROS 7) it will fail to form neighbors with two distant routers on different interfaces if those two routers have the same link local address facing the MikroTik. It will only form with one of them and you will get errors.
 
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ZeroByte
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Re: OSPFv3 adjacency with Cisco routers

Fri Aug 30, 2019 5:32 pm

I could probably work around it by running two OSPFv3 instances, but since we're not really doing much with IPv6 for our customers yet, I'm not too concerned. If one link goes down, the other should form adjacencies and converge within 45 seconds or so. I was just kind of curious if anyone had seen similar behavior.
When given a spoon,
you should not cling to your fork.
The soup will get cold.
 
mducharme
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Re: OSPFv3 adjacency with Cisco routers

Thu Oct 24, 2019 8:38 am

FYI, this seems to be fixed in v7 beta.

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