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reply to raytaylor

Re: Microtik and IPv6

Thanks for your reply

They will be ubnt rockets for the WDS backhauls so if the wireless link goes down, the ethernet will stay up. I am hoping it has some way of detecting that it cant talk to the next router in the loop and then cut the link.
I have seen a feature request in the ubnt forums that if a wireless link goes down, they want the rocket to cut the ethernet port also - i assume this is what you are talking about for the physical interface.

He said this was because he didnt want to wait for OSPF to detect the link was down and needed it to respond instantly, where as i dont mind if it goes down for 30 seconds while it waits for some sort of ping? to fail and then start using another path, while rechecking the link every minute or so to see if it is back up.

Cant seem to find any specific info on how this would work if the ethernet port stays up (to the radio) but the radio link goes down.


Siren, WI
I use OSPF for failover for my two links to my upstream provider. One is a direct PTP shot which plugs into my core router, and the other is a shot to one of their other towers which runs over a VPN back to the same core router to make it look like both links are simple PTP shots.

I have the hello interval set to 1 second, and the router dead interval set to 5 seconds. That basically means that it will check the link every second to make sure it is still online, and if it doesn't respond for 5 seconds, it will failover to my other link.

I tested it down to 2 or 3 seconds, which worked, but caused some excessive flopping if I had any packet loss. 5 seconds has worked will for the last 2 years. You'll drop a few pings, but other than a little delay waiting for a page to load, the failover typically happens before most streaming video sites even run out of their buffer.

Bernie, MO
reply to raytaylor
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OSPF has a 'hello' packet that is sent at a set interval (10 seconds by default). If a 'hello' packet is not recieved by the time the 'dead' (40 seconds by default) time limit is reached the link is considered to be down and OSPF will reconverge. This is what happens if the radio's are up but the RF portion is not passing traffic. So it will work in the way you are describing - basically the link is dead for 40 seconds, then the traffic reroutes.

Attached is a picture of my active & planned wireless backhauls. I use OSPF for the IGP.
I survived Hale-Bopp!