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astounding
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RouterOS equiv. of Cisco's "ip ospf mtu-ignore"?

Wed Dec 09, 2009 12:04 am

Is there a RouterOS equivalent to Cisco's "ip ospf mtu-ignore" to tell a MikroTik to ignore MTU mismatches? (4.x or 3.x...)

Thanks!

Aaron out.
 
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sergejs
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Re: RouterOS equiv. of Cisco's "ip ospf mtu-ignore"?

Wed Dec 09, 2009 2:29 pm

As far as I know, there is no such feature in MikroTik RouterOS OSPF.
MTU is only adjusted for PtP links.
 
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astounding
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RouterOS OSPF ignore MTU mismatches?

Wed Jun 23, 2010 1:05 am

Any progress on implementing an OSPF MTU-ignore feature for RouterOS's ospf and ospf-v3?

Currently I cannot get a Cisco and a RouterOS box to talk OSPF to each other over IPv6 due to MTU mismatches. But likewise due to other (currently working) devices on the segments in question, I cannot reduce the Cisco's MTU to match the MikroTik, and the 'Tik's MTU cannot get any larger.

Here's what I see in the logs:
22:00:46 route,ospf,info Discarding Database Description packet: too large MTU 
22:00:46 route,ospf,info     mine=1524 
22:00:46 route,ospf,info     received=1546 
Cisco routers can ignore MTU mismatches quite easily and establish working OSPF sessions with other devices, just not RouterOS boxes... yet...

Here's hoping the Mikrotik people add an option like "/routing ospf-v3 interface set 0 mtu-ignore=yes" in the near future...

Aaron out.
 
ElNecio
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Re: RouterOS equiv. of Cisco's "ip ospf mtu-ignore"?

Wed Oct 03, 2012 9:44 am

I know it is an old post that I am replying to but it is one without a resolution......

FYI I got around this problem by setting the MTU on the ethernet interface that hosts the OSPF instance equal to the "received=" value shown in the log.
 
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Eising
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Re: RouterOS equiv. of Cisco's "ip ospf mtu-ignore"?

Thu Oct 04, 2012 10:16 pm

You shouldn't have mismatching MTU's on links anyways, so you'd best just fix the MTU and then as an added bonus, you'll avoid all the ugly issues that arrise when you have an MTU mismatch.
The road to hell is paved with good intentions.

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