DHCP suddenly broken with no change to Mikrotik config

RouterOS General
1

Hello,

After several rock-solid years on my Mikrotik I’ve apparently started hitting “if it can go wrong, it will.”

I run DHCP with failover on two nodes (not on the Mikrotik). DHCP services live on VLAN1001, and I have relays set up on the Mikrotik for each of my other VLANs. Up until today, this was working great.

All of a sudden this afternoon, DHCP broke down. DHCP server logs show DHCPDISCOVER being received and DHCPOFFER being sent, but no DHCPREQUEST or DHCPACK activity.

I made no changes on the Mikrotik anywhere near where this occurred; the only even-close-to-relevant thing that happened in the meantime is that I took the secondary down to reimage, and I confirmed once it came back up that it was communicating with the primary (and both servers showed the same activity as previously described).

Any thoughts on what might have occurred here? I have a single bridge set up, and all VLANs utilize the bridge to communicate between ports. Again, this setup was 100% working for months until this afternoon, and I’m just at a complete loss right now.

I can provide any logs/configs needed to troubleshoot, just don’t know what would be useful in this situation. Thanks.

//edit: RB4011, ROS 7.11

2

If I was in your shoes, I’d fire up wireshark and look for the place where DHCP packets disappear. Running sniffer tool on ROS should help as well. Only after you determine where exactly things go haywire it’s possible to start thinking about solutions.

3

Just wanted to leave a note for anybody else encountering this issue that the ROS 7.11.2 upgrade and the accompanying firmware resolved this issue.

4

http://forum.mikrotik.com/t/v7-11-2-stable-is-released/168778/1 is announcement post showing DHCP is only 7.11.2 fix.

5

That note is specifically regarding the DHCP server, which I do not use; I use the relay functionality.

I think ultimately my issue was related to the VLAN/bridging breakage in 7.11.0 that was fixed in 7.11.1, but I jumped straight from 7.11.0 to 7.11.2, so that’s all I’m claiming. :slight_smile:

6

Thank you for taking the time to grow our collective knowledge.