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dboreham
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IPv6 static routes mysteriously vanish

Sun Aug 18, 2013 6:17 am

Anyone else seeing this? It has been happening on one of our routers (RB600A) for at least a year. With increasing deployment of IPv6 on our network it is becoming more and more irritating. Upgraded the unit to 5.25 today, and the problem is still present.

Symptoms :

1. Configure several static IPv6 routes (route each of several IPv6 subnets to specific hosts on a local subnet).
2. Observe traffic flows as expected, often for weeks and months.
3. Make some random configuration change on the router (e.g. change shaping setup, or sometimes it seems to just happen spontaneously).
4. Observe that traffic is being dropped for one of the routed IPv6 subnets.

Workaround : reboot the router, or (discovered by chance), if the "bad route" is disabled then re-enabled, it will magically start working again.

Packets seem to get dropped, rather than rejected, when the dropped route syndrome is active.

It feels like a bug where the mapping of the router's config state down to Linux ip/route commands is broken under some conditions (I have no idea if ROS actually works that way, btw). Flipping the route off and on forces explicit reinstatement of the route in the routing table underneath.

Nothing interesting in the log.
 
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janisk
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Re: IPv6 static routes mysteriously vanish

Mon Aug 19, 2013 4:34 pm

can you see this behaviour in 6.2 also, could you send support output file to the support when route is not working properly?
 
dboreham
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Re: IPv6 static routes mysteriously vanish

Tue Aug 20, 2013 6:30 pm

can you see this behaviour in 6.2 also, could you send support output file to the support when route is not working properly?
I don't have any 6.x deployed. Is it safe to upgrade these older boards from 5.x ? (this is an RB600A)
I'll generate the support file next time it happens (we now have Nagios alerting on the loss of the IPv6 route, so it will be easier to spot quickly).
 
dboreham
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Re: IPv6 static routes mysteriously vanish

Fri Aug 23, 2013 9:48 pm

Good news : it happened again. This time I was able to correlate the timing of the nagios alert with the RB600A log to discover that the RB had spontaneously rebooted (reason unknown). The loss of IPv6 routes occurred presumably because they were not restored in the reboot. As before, disabling and re-enabling each route in winbox brought all the routes back.

I have the supout files (both before and after route restoration) and will send to support.
 
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dohmniq
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Re: IPv6 static routes mysteriously vanish

Sat Aug 24, 2013 3:06 pm

I was going to reply to this thread earlier but wasn't sure if my case was relevant.
However, now that you've mentioned rebooting then I can say I've hit the same problem.

In my case it's on a ROS 6.1 RB435 and it's the static ::/0 ("default") route that I need to disable/enable each time after reboot.

This is a HWMP+ mesh setup and maybe I don't need the "default" route because packets should find their way to portal mesh nodes?
Without the static default route packets don't make it to the internet though.

Not sure if OP is using meshing but I can drive there and product supout files if you think it would help?

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