Subscriber Module disconnected - No GPFs


I have both AP Sync and SM with 2.2 release, on SM under Monitor>Wireless i can read this.


Anyone know what happens?

Thanks in advance

Are both software banks the current FW on the AP?  Seems like a file system error from what I am reading just in general research, but not Cambim ePMP specific.  If it was on my network I would like re-load the FW on the AP twice and verify the AP settings.

Yes same 2.2 Release on both banks. Will  try reinstalling it.



Can you please post a screenshot of the entire table? It appears that those three rows are for three different APs and the subscriber appears to have connected to one of them (the row that shows "Success"). 

What is the issue? Is your SM not connecting to the AP?

Regarding the title of your post. GPFs are control/management messages sent from the AP to the SM. These control messages are sent at the lowest MCS (MCS 1 or MCS 0 if explicitly configured under Configure->Radio). No GPFs mean signal from the AP is not strong enough or there is severe interference on that channel causing the SM to miss GPFs from the AP. If fthe SM misses GPFs from the AP for 600ms, it will disconnect. 



I'm just tossing out ideas, another could be verify country codes on each unit?  Seems like that error being so odd would come from corrupted file system or mismatched data.  Good Luck, hopefully Cambium can also provide some information.

Hi Ben, 

Yes, these are good suggestions. Country codes may affect the Tx power of the AP. No GPFs are a direct result of issues in the RF environment. 



Hi Sriram,

It looks like not a interference on channel, it looks like a problem with MTU, system log on SM said to me,  (attached boxes). My pppoe server is with 1480 MTU and 1480 MRU, its a routeros. I have change both Ether and pppoe MTU to 1480 under Configuration >Network on SM but still same error on system log.

Probably this miss configuration is the reason for other erros, trying to resolve this first.

About your question, i have 3 APs, 1 is a link the other 2 are Sectors sync,SM can connect to both sectors with Diff SSID, first prefered AP is which has the No GPFs message, SM connected to second prefered AP.


Unable to complete PPPoE Discovery

Interface ath0 has MTU of 1480 -- should be 1500.  You may have serious connection problems.


Just upgrade to 2.3 and SM connect to first prefred AP, it happens before with 2.2 when restart AP, i need to leave the system some hours to see if this SM gives same error when connecting to first prefered AP and connect again to second prefered AP.


Will open a new post for MTU problem.

Hi all,

Since my last post the SM is still connected to the first prefered AP and no error about GPFs present. Will continue monitoring it.



hi all

any solution to this?? just change the mtu??

ive got also 2 mikrotiks connected through a ptp with 2 epmp 1000

i have also the same problems with version 2.3.3


Hi Miguel and GINEBRA254,

With regard to the syslog message:

"Interface ath0 has MTU of 1480 -- should be 1500.  You may have serios connection problems",

this is not causing any problems with establishing a PPPoE connection, but is a bad error message.

ePMP allows for the MTU to be set up to 1492 bytes.  Additionally, a PPPoE header of eight bytes is added providing a total of 1500 bytes.  The piece of software with this error message is looking at the value entered in for the entered MTU and if it is anything less than 1500 (which it always is), is logging this error message which meant it always logs the error message.  The message indicating that you may have a serious connection problem is not correct and should not be present.

This error message will be removed with release 2.4.0 and replaced with another information message that confirms the value set by the user.

There was another message in this chain that read:

"Unable to complete PPPoE Discovery"

This is a valid error message that was indicating something else that was not set up correctly. Unfortunately, I do not know at this moment what this was that could be causing Miguel a problem and we would need further information.


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Hi Daniel,

About "unable to complete pppoe discovery"

It happens in some SM's even using same firmware version, i have noticed that some SM's take the correct values and others no when attached to same Sync AP.

What i have done is to setup my pppoe Server with DNS on same subnet and now all working. But the error can be reproduced if you try to assign for example from pppoe Server a DNS like google's , SM's sometimes doesnt take right values and second IP for management take default ips even when this option is disable.

Hope this will help to find the trouble

Thanks in advance

Hello Miguel,

It is possible for the "unable to complete pppoe discovery" error to be displayed if the wireless link between the AP and the SM has not been established but the process that manages the pppoe connection is already attempting to initiate a pppoe session. In such case the pppoe session attempt may not be successful and the error above will be printed in the syslog. This is a normal scenario, as the wireless link needs to be up and running before the pppoe session can succeed.


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Hi Luis,

You are right, when i receive the pppoe connection from SM it is unaccesible for a few seconds till the wireless link becomes totally available, maybe a link check before to start the service will be needed to be added.