Hi guys, we are having an issue with a new setup which I was hoping somebody might be able to help with.
We have a new LNS setup with redundant cisco routers and cisco switches behind them in an MPLS setup.
We then have a Mikrotik RB1100 plugged into the switches, all the switches and 2 LNS's do is give us a redundant feed to our network which we terminate DSL tails on.

OSPF is setup in the cisco routers and switches, with a /31 network between the RB100 and the LNS routers, the problem is that when I setup OSPF on the Mikrotik I see the routes in the routing table correctly, but they complain that the gateway, which is shown correctly, is unreachable.

I cannot ping any addresses in the LNS environment, no loopbacks or physical addresses, however if I add a manual static route into the RB1100 I can get to the IP in the LNS setup straight away.

On the RB1100 I have setup one instance and one network, the interfaces are dynamically created by doing this.
The instance is configured to redistribute default router always as type 1, this is because our default route is via BGP from the RB1100 to our transit operator, it is also configured to redistribute connected routes, BGP routes, and other OSPF routes as type 1.

Filters are not in use, and I have recreated everything from scratch with pretty much the defaults and it makes no difference.

I have also tried creating the interfaces manually, but that made no difference either.
The RB1100 is running ROS 4.13 and is only used as a router and nothing else.

If you have any suggestions I would really appreciate them as I have run out of ideas and desperately need to get this setup to work, and work really soon

Thanks
Paul

There was a thread a while ago about /31s not working on RouterOS. The error message you're getting seems related.
http://forum.mikrotik.com/viewtopic.php ... 5&p=250332

Are you able to expand to a /30?

Thanks, yes I did see that post, the poster mentions that they couldn't ping, I can ping across the /31 OK but the routes don't install into the routing table properly.
Maybe somebody from support would respond about the /31 support with OSPF ?

Regards
Paul

If you want to make sure support sees it make sure to email support@mikrotik.com - these forums aren't an official support channel. They might or might not read this thread, and might or might not respond if they do.

Well we configured the link between the Cisco LNS routers and the RB1100 with /30 links today and OSPF is happy.
So, although the RouterOS seems to support /31 links, it doesn't support them with OSPF, or at least with OSPF to a Cisco.

Perhaps an upgrade to a newer ROS version will fix it, however for now we will just have to waste a couple more IPV4 addresses

regards
Paul

RouterOS does not support /31 addresses. If you don't want to waste addresses set up point to point link with /32 addresses.

The strange thing is though it works fine until you want to use OSPF, so something works, but just not 100%.

Regards
PAul