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Community Member

7921 and 7925 IP Phones often registers on SRST Gateway

Hi,

On a branch office, I have 7921 and 7925 IP Phones. The phones often go to SRST mode and when this occurs, the call is dropped.

On headquarter, I have a CUCM 8.6(2)

On branch office, I have a 2801 gateway (IOS 15.1.4M), a WLC 4402 (IOS 7.0.230.0), 5 APs (3x AIR-LAP1242G and 2x AIR-BR1310G). The firmware version running on IP Phones is 1.4.2. I'm using WPA2 + AES and TKIP encryption (no radius server). There is a voice VLAN with Platinum QoS on the WLC.

There is no WIFI connection loss on the phones (don't see the 'Leaving Network Area' message on phones).

There is no connection loss with the CUCM on headquarter.

No packets seems to be dropped on the WAN.

I see the phones registering on the gateway, and after 2-3 minutes, they return registering on CUCM, and so on, randomly. Not all the phones registers on the gateway at the same time. One phone can register on the gateway, then returns to the CUCM...

Qos is set on the 2960 switches.

I see in docs that WMM should be set. On the WLC, WMM is set to 'Allowed'. Should it be set to 'Required' ?

Thanks for help...

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13 REPLIES
Community Member

7921 and 7925 IP Phones often registers on SRST Gateway

I forget!!!!

I also have 2x 7941 phones (firmware 9.2.3) and I don't have problems with this two!!!

7921 and 7925 IP Phones often registers on SRST Gateway

I have seen the same thing on CUCM 8.0.3 and 7921 running 1.4.2.

Cisco Employee

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

You should look to upgrade to 7.0.235.0.

There is an open issue in 7.0.230.0 in regards to broadcast key rotation.

Sent from Cisco Technical Support iPhone App

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

I am on 6.0.202.0.  Do you have a bugid for the above mentioned key rotation issue?

Cisco Employee

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

The caveat mentioned (CSCtz19309) is applicable to 7.0.230.0 only and my response to the original submitter.

No issues with 6.0.202.0.

But maybe you should consider upgrading to 7.0.235.0 as well.

Sent from Cisco Technical Support iPhone App

Community Member

7921 and 7925 IP Phones often registers on SRST Gateway

I've upgraded the CUCM from 5.1.3 to 8.6(2a), and I've upgraded the WLC from 6.0.196.0 to 7.0.230.0.

Perhaps, upgrade of the WLC was not necessary, so I wonder if I should upgrade to 7.0.235.0 or downgrade to 6.0.202.0!!!

I'll let you know if my problem is resolved.

Thanks Migilles for help

Cisco Employee

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

Use 7.0.235.0.

Sent from Cisco Technical Support iPhone App

Community Member

7921 and 7925 IP Phones often registers on SRST Gateway

Ok...

On headquarter, I also have a WLC with the same firmware, and with 7921 and 7925 IP Phones. But I don't have this problem.

So I don't know if there is a problem on the WAN, or on the WLAN!!!!

Community Member

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

Upgraded to 7.0.235.0, but no effect!!!

Just one question : When a phone send a keepalive packet, is there a deadline for receiving the ACK packet ?

When pinging phones ,whether on the Headquarter or on the branch office,  the average delay is 650 ms!!!

But when I ping the branch router, there's no problem (average delay 35 ms).

An idea ?

Community Member

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

Hi,

Can someone tell me how and when the registration on SRST gateway occurs ?

According to me, IP Phone sends keepalive packets to CCM and when some consecutively are not acknowledged, IP Phone considers that connection to CCM is lost and tries to register to SRST Gateway.

Is this true ?

Community Member

7921 and 7925 IP Phones often registers on SRST Gateway

Hi!

This seems to be quite old discussion but I have ran in to same situation recently with CUCM 8.5 and 7925 phones in branch office. Ping times "normally" about 500ms and sometimes even more than 1000ms!

Is there any solution for this...?

br Satu

Cisco Employee

7921 and 7925 IP Phones often registers on SRST Gateway

Ping times can be up to 1000 ms when connecting to a CCX enabled AP that advertises the Proxy ARP IE.

This allows the 792x phone to enter deep sleep vs having to wake up at the DTIM period.

Should wake up at least every 1000 ms though to check for incoming packets.

As far as the SCCP keepalive handshake, it is as the following:

Phone > SCCP Keepalive > CUCM

CUCM > SCCP Keepalive ACK > Phone

Phone > TCP ACK > CUCM

A phone will send a Keepalive to the primary / connected CUCM every 30 seconds; secondary CUCM or SRST every 60 seconds.

In the instance of the 792x phone, if it doesn't receive a SCCP Keepalive ACK after 3 attempts (after 90 seconds), then the TCP session will be terminated.  

This can then trigger the phone to attempt to register to a secondary CUCM or SRST.

On the flip side, if CUCM is sending a SCCP frame inbound to the 792x phone, then the phone must ACK that frame; otherwise it risks having the TCP session terminated.  CUCM will retry a SCCP frame 2-3 times only and could exhaust the retries within a few seconds.  If max retries is reached, then the TCP sesson will be terminated and the phone could attempt to register to a secondary CUCM or SRST.

The recommended 792x versions are 1.4(4) / 1.4.4.3; but at a minimum use 1.4(3) / 1.4.3.4.

And for the WLC it is recommended to use 7.2.110.0, 7.3.101.0 or 7.4.100.0.

If you continue to have issues, please open a support case with Cisco TAC.

Community Member

Re: 7921 and 7925 IP Phones often registers on SRST Gateway

Hi,

I find out a solution.

When disabling session timeout  on WLC, it works...

Thanks all for help...

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