I work for a WISP and we use Mikrotik RB1100AHx2 routers at our towers. We also use Ubiquiti wireless gear. I am having issues with our CPE’s dropping the PPPoE connection with the routers. I don’t even know where to begin to troubleshoot this issue. I did some Googling and found some old posts in the Mikrotik forums that suggested OSPF to be the issue. But I am pretty sure that Mikrotik would have fixed that issue since the posts were seven years old. Here is what I am seeing in the Nanostations log file.
Jun 2 09:13:18 pppd[1038]: No response to 5 echo-requests
Jun 2 09:13:18 pppd[1038]: Serial link appears to be disconnected.
Jun 2 09:13:18 pppd[1038]: Connect time 11553.9 minutes.
Of course the connect time varies, there is no definitive time between disconnects. Any help would be appreciated. Thanks.
I’m just guessing at your setup here, but the PPPoE server is probably at the tower? If not, the tower would be the best place for it. The link to the end device had to be a 100% transparent bridge. With UBNT devices, you need to have the Multicast Data turn on so that it is passing all of that traffic all of the way through to the end device. PPPoE is fragile by nature, so if you are having wireless problems, or interference problems, you will likely seem them there first. To troubleshoot, work your way out from the PPPoE server with a PPPoE client and see at which point it starts breaking down. You will find that most of the time, its a layer one problem.
rickfrey, thanks for the reply. I do have ‘Multicast Data’ set to ‘Allow All’ on all the AP’s and CPE’s on our network. And yes, the PPPoE server is at each tower. 
I will keep investigating and see if I can find anything. Could you give me some examples of wireless problems and interference issues that you may have run into that could be breaking the PPPoE connection?
You don’t need multicast for pppoe. I suspect that the wireless is dropping and the tunnel is dropping with it. Try a longer keep alive timeout which may give the wireless a chance to reconnect before dropping the pppoe tunnel. You may have better luck with WDS on the wireless so it is truly bridging if it’s not already WDS. I have had disconnect issues with using tkip encryption on the UBNT radios so if your using tkip then change that to AES which is much better in multiple ways. I have found that most of the time the issue is bad connections on the ap. If you have any really bad connections even if it’s another subscriber that may be the issue.
Joshaven Potter
http://joshaven.com
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