What Does "Unable to get host name..." Mean

"Unable to get host name from xxxxxxxxxx.cloud.cambiumnetworks.com"

I have a couple of SMs that fell offline and won't recover.  Reboot does not help.

What is this an actual indication of?  The  SMs are communicating with the cloud server, as I can see the handshake, right up to the point where I get this error.

This may mean that your SMs cannot contact the cloud server hosting your account.  All *.cloud.cambiumnetworks.com URLs need to be whitelisted for ports 80 and 443.  Check if your firewall is blocking this traffic.

Is this on PMP or ePMP ? Please check your DNS settings in SM, DNS resolution of redirected URL from cnMaestro  is not working.

Thanks for the replies.

This is on two PMP 450 SMs.

Unfortunately, DNS resolution is fine and all other units operate correctly.  The only way, I can see, for the cnMaestro agent to get the account specific part of the domain (xxxxxxxxxx.) is for the unit to communicate with the cloud server.  Am I wrong?  Why does merely deleting the unit from cnMaestro, with no firewall manipulation, restore the connection?  What is the "hostname" that should be being passed by the server to the agent? 

Looking through the agent debug log, I can follow the entire agent/server handshake right up to the point where the hostname request is made.  The agent is clearly communicating with the server right up to this point.

Yes, the device connects initially with cloud.cambiumnetworks.com and then gets routed to the cloud server hosting your account (xxxxxx.cloud.cambiumnetworks.com).  So the device is connecting to the initial cloud server but does not connect to the other server hosting your account. 

Is your device able to ping and DNS resolve the xxxxxx address?

Can you explain the issue with restoring the connection by deleting the unit from cnMaestro?  I did not see this mentioned in your other post.

If you want to send me your device agent debug log I can provide some feedback on what might be going on but it sounds like you are pretty close to the answer already.  jordan.stipati [.at.] cambiumnetworks.com

Is your device able to ping and DNS resolve the xxxxxx address? - Yes

Can you explain the issue with restoring the connection by deleting the unit from cnMaestro?  I did not see this mentioned in your other post. - These units were previously onboarded (about 6 mos) - I deleted them from cnMaestro, causing them to have to be approved for onboarding again. 

If you want to send me your device agent debug log I can provide some feedback on what might be going on but it sounds like you are pretty close to the answer already.  jordan.stipati [.at.] cambiumnetworks.com - Will do

Please do a DNS test for not working hostname XXXX.cloud.cambiumnetworks.com.

Have you tried rebooting the SM ?