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Beginner

CP-8841 fast busy and drops registration

Hi everyone,

 

I've got 8841 phones at one of my customer offices that are not able to make or receive calls. The phones will receive IP addresses and register in CM but when called or attempting to call out will fail with either silence or a fast busy. I'll then see it drop registration in CM and after a few minutes it will come back. Other offices on the same call manager in different regions are working just fine. 

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Accepted Solutions
Beginner

Re: CP-8841 fast busy and drops registration

Resolved: Was simple MTU again. Base MTU was set to 1300 but no adjust-mss. Once we implemented that it ran stable. No users on site now to verify but I'll post again if different.

View solution in original post

7 REPLIES 7
VIP Rising star

Re: CP-8841 fast busy and drops registration

You should narrow down the problem:

- Does registration flap for all phones at that site?

- When a phone is registered, can it dial another phone at the same site (check partitions/CSSs/DPs accordingly)?

Georgios
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Beginner

Re: CP-8841 fast busy and drops registration

I got results back from that customer after I posted:

Existing SCCP phones do not flap or drop or behave in anyway like the 8841 SIP phones are

8841 phones are unable to dial in building and vice versa. When they try they get the same behaviour of a fast busy or silence and the phone(s) re-register.

Beginner

Re: CP-8841 fast busy and drops registration

Additional details we've found:
Status message view shows TCP Timeouts, not shown at other offices
Debug view shows Reason 10 and 18 for reason for out of service. Details on what those mean I found elsewhere:
10 -- TCPtimedOut - The TCP connection to the Cisco Unified Communication Manager experienced a timeout error
18 -- TCPclosedConnectHighPriorityUcm - The device closed the TCP connection in order to reconnect to a higher priority Cisco Unified CM
Beginner

Re: CP-8841 fast busy and drops registration

Resolved: Was simple MTU again. Base MTU was set to 1300 but no adjust-mss. Once we implemented that it ran stable. No users on site now to verify but I'll post again if different.

View solution in original post

Beginner

Re: CP-8841 fast busy and drops registration

MTU where? On the L2 switch the phone is connected to ?

Beginner

Re: CP-8841 fast busy and drops registration

On the GRE tunnel leaving the site router to the next hop. The phone was defaulting to a higher value than the circuit was capable and without the mss adjust it wasn't correcting the phone.

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Beginner

Re: CP-8841 fast busy and drops registration

Thanks. That doesn't apply to my circumstances then.


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