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IP Phones polling gateway router causing tcp resets?

We have a 3640 router acting as an voice Gateway.

It is running Version 12.2(4)T1.

We have our IP phones running the skinny protocol.

When doing a debug ip tcp transactions in the 3640, it appears that all our IP phones are sending tcp packets (port 2000) to the gateway. Why the gateway? It is not the call manager..

And the gateway is generating TCP Resets. This appears to be causing some congestion.

5d21h: TCP: sent RST to 207.70.188.77:52101 from 207.70.188.94:2000

5d21h: TCP: connection attempt to port 2000

5d21h: TCP: sending RST, seq 0, ack 3950952449

5d21h: TCP: sent RST to 207.70.188.67:52510 from 207.70.188.94:2000

5d21h: TCP: connection attempt to port 2000

5d21h: TCP: sending RST, seq 0, ack 4032573441

5d21h: TCP: sent RST to 207.70.188.68:50793 from 207.70.188.94:2000

5d21h: TCP: connection attempt to port 2000

5d21h: TCP: sending RST, seq 0, ack 3958073345

5d21h: TCP: sent RST to 207.70.188.78:50098 from 207.70.188.94:2000

Thanks,

Brent

2 REPLIES
Bronze

Re: IP Phones polling gateway router causing tcp resets?

Starting with 3.1, the phone loads support a feature called SRST. This allows the phones to register to the local router in the event of a WAN link failure.

Prior to 3.1(3a), phones that do not have a backup CM will try to establish a connection to the default router in order to have a backup link. This is the behavior that you are seeing.

In 3.1(3a) we introduced an option in the phone configuration page called "SRS Telephony" this allows you to control whether a phone will register with their default router or not.

So, in your case, you will need to upgrade to 3.1(3a) and set the SRS Telephony option to Disabled for each phone.

-Dustin

New Member

Re: IP Phones polling gateway router causing tcp resets?

SRST sounds like something interesting we'll test out

sooner or later. Thanks for the info. We'll upgrade to 3a.

Thanks,

Brent

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