Max MTU keeps jumping lower (router reboot fixes it) - fix?
Posted: Sun Nov 28, 2010 5:43 pm
Hi everyone,
I've been using MT routers for a few years now and generally everything works very well.
I have one customer where I've given them a point-to-point type link with a 750G at both ends in their two premises. I'm using an EOIP tunnel on my private WISP 172.16/16 network and then I'm bridging the EOIP interfaces to ethernet ports on the routers. I set up this type of layout quite a lot and it normally works flawlessly for me.
But with one link I'm having the weirdest problem which as occurred on both routers (both sides of the link): -
Normally (when I have an IP set to the bridge in the router for testing) I can ping devices on the customer's network with MTU set to 1500 and no-fragment on.
About every two days something goes wrong and I can only ping the customer's devices if I ping with the MTU under 1,000 (nine hundred and something - I can't remember the exact number). The only way I can fix this is by rebooting the Mikrotik and, after that, the 1500 MTU pings go through again fine. Right now I'm on the latest ros 4.13 but it doesn't seem to matter what 4.X version I'm on. There is nothing at all in the log and disabling/re-enabling the ethernet or bridge interfaces doesn't make any difference.
This is weird - has anyone else seen this?
Right now I'm thinking about trying to put in a script so that if the MTU 1500 ping fails I just reboot the router but I'd much rather just have a better (no reboot) fix for this problem.
thanks for any help!
Derek
I've been using MT routers for a few years now and generally everything works very well.
I have one customer where I've given them a point-to-point type link with a 750G at both ends in their two premises. I'm using an EOIP tunnel on my private WISP 172.16/16 network and then I'm bridging the EOIP interfaces to ethernet ports on the routers. I set up this type of layout quite a lot and it normally works flawlessly for me.
But with one link I'm having the weirdest problem which as occurred on both routers (both sides of the link): -
Normally (when I have an IP set to the bridge in the router for testing) I can ping devices on the customer's network with MTU set to 1500 and no-fragment on.
About every two days something goes wrong and I can only ping the customer's devices if I ping with the MTU under 1,000 (nine hundred and something - I can't remember the exact number). The only way I can fix this is by rebooting the Mikrotik and, after that, the 1500 MTU pings go through again fine. Right now I'm on the latest ros 4.13 but it doesn't seem to matter what 4.X version I'm on. There is nothing at all in the log and disabling/re-enabling the ethernet or bridge interfaces doesn't make any difference.
This is weird - has anyone else seen this?
Right now I'm thinking about trying to put in a script so that if the MTU 1500 ping fails I just reboot the router but I'd much rather just have a better (no reboot) fix for this problem.
thanks for any help!
Derek