100Series Access Points - Power 140AC from 145AC

[Marcus_LNS]

Hi,

  I have a small network with a 145AC unit and 2 x 140AC. If they are all plugged into my PoE switch they all work together well (with the 145AC as the Preferred Master).

  To make cabling easier, I would like to plug one of the 140AC units into the 145AC PoE port. The 145AC is powered from a GS408EPP and as expected when I plug the 140AC into the 145AC it powers up and boot OK to a steady green light. However it does not join the mesh network with the other units. It seems to run in isolation to the other units. 

  Is this behavior because the 145AC ethernet connection an RLAN?  Is it possible to configure the 145AC to allow the 140AC to join from its PoE port (e.g. by bridging that port?)

[marce1000]

 - Configure and use a syslog-server , use debugging level : https://www.cisco.com/c/en/us/support/docs/smb/wireless/CB-Wireless-Mesh/2064-Setting-Up-System-Message-Logs-CBW.html

                                     Then cold-boot the ap and followup on the logs.

 M.

[Marcus_LNS]

Hello,

  Thanks for the tip. I have collected a log from the system and found that the 140AC does join for a brief period. (Once I knew this I could see this on the web interface for a few minutes after powering up the 140AC.

The log then shows a heartbeat reply missing and a resulting disconnect due to Echo Timer Expiry. 

As I mentioned before - the 140AC works OK if plugged into the same switch as the 145AC - this problem only happens when it is plugged into the 145AC PoE port. 

Do you think this is expected behavior - i.e. should the 140AC work OK plugged into the 145AC PoE socket? If this is not expected and the configuration should be working OK possibly the PoE connection to the 145AC might have an issue?  

Full log below.

BTW. When I tried using the web interface log viewer - I could see the message as below - until the 140AC disconnected and then the log was cleared.

[marce1000]

                         - You should try to figure out if the can provide sufficient power for the 140AC 

 M.

[Marcus_LNS]

Hi,

  OK I have checked a couple of things in terms of power. Firstly I have checked the cable connection between the GS408EPP switch and the 145AC unit and in terms or resistance etc it looks good. Just to be sure I have also tried a different cable between them. I still get the same behavior.

 In terms of PoE power budget, the GS408EPP spec states 124W total PoE power, with PoE+ (802.3af & 802.3at) on each socket (30W limit). I am currently only powering the 145AC and another switch from this (the switch max power draw is 22W). 

  The 145AC power requirement is 8.5W for itself. It can pass on 802.3af (Class 0) as it is powered by 802.3at switch. The 140AC requires 8.3W maximum.  

  Looking at the switch I can see that a 140AC PoE is declared as Class 0 and is taking 3.2W running. The 145AC (with another 140AC powered from it) is declared as Class 4 taking 8W. No errors shown.

[marce1000]

 - You may try a native cisco switch as the 'source for all power' just for testing , check if that helps.

 M.

[Marcus_LNS]

Unfortunately I do not have a Cisco switch to use as the power source.

However I think I have proved that it is not a power issue.

I have powered the 140AC with a DGS-1008P switch as it's power source. 

Upstream of that I have added and removed the 145AC unit. I have re-powered the 140AC unit each time I swap in/out the 145AC in the upstream network.

Consistently with the 145AC upstream - the 140AC will join and then leave the AP group.

Consistently without the 145AC upstream - the 140AC will join and remains in the AP group - I have waited over 1 hour and it remains.

So it appears that it is connecting to the 145AC ethernet that is the issue - not power.

[Marcus_LNS]

As another data point - I have tried inserting another PoE switch between the 145AC and the 140AC device (a DGS-1008P) which has its own power supply and provides PoE+ power. The 140AC still does not stay joined to the full mesh. (I provided logs on this thread that shows it does join initially then drops off again). So I don't think it is a power issue. It seems to be related to the Echo Timer Expiry.

[marce1000]

 - Attach a console to the 140AC and perform a cold boot, scrutinize the boot process , watch for any sort of errors , if any.

 M.

[Marcus_LNS · Accepted solution]

Hi,

  Thanks for your help. I managed to get a TAC case opened with Cisco and they have confirmed that my network configuration will not work. 

This configuration will not work.  It’s not a PoE issue, it’s a VRRP issue. 
The CBW145 doesn’t send the VRRP packet that are used to locate the primary AP out any of its bridged ethernet ports.  Because of this the 140 will never find the primary AP on the network.