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ZD1100 remote AP's upgrade problem

New Contributor II
We have ZD1100 managing 8 AP's, few are connected on the same LAN as the ZD, and the others are on remote site and reach the ZD via IPSec VPN.

I upgraded the ZD from 9.5.1 to 9.7.1, it seemed to work well and the directly connected AP's upgraded fine to 9.7.1. The problem is that all remote AP's got stuck in the state: "Upgrading firmware" and did not pass this stage (they were still reachable but did not connect any clients).

I did a rollback of ZD to 9.5.1 and all AP's were back online.

The remote AP's has full access to the ZD over the VPN and normally act with no problem. Any idea why the firmware upgrade of remote AP's might fail? Anyone with a similar setup?


Valued Contributor II
Hello Yuval,

Thanks for your feedback. Keep us posted as it would interesting to see what causes it.

Best of luck

New Contributor II
Just an update:
I did the following which resolved the issue:
1. Set "Tunnel MTU" option to 1400
2. Reboot remote AP's
3. Upgrade ZD to

After the ZD came up, all AP's were upgraded successfully.
I am not sure what solved the problem but I have a feeling that it's the change of firmware to 9.6.2, there might be some issue with 9.7.1

Valued Contributor II
Thanks for the update. Yes, i also agree something may have changed. Reading the release notes for 9.7.1 at PDF page 6

There is a mention of "5.1.5 - Resolved an issue with APs being unable to join ZoneDirector due to the default MTU size set on Zone Director running on version 9.6 . (ID ER-929)"

this is my guesswork, you may not have seen this issue in 9.6 however there was something related in 9.6 which got fixed in 9.7.1 however now you may be seeing the manifestation of incorrect fix. again this is my guess nothing for sure.

New Contributor II
It's very well possible, but I guess I will leave it be with 9.6.2 for now as it is also the recommended release. As the saying "It works, don't touch it" 🙂