3845 SIP gateway high cpu due to interrupts

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Apr 16th, 2009
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We have just put some numbers on our SIP gateway and the processor is showing high cpu due to interrupts.

It is going as high as 100% depending on the load.

We are seeing anywhere from 50 to 75 inbound calls at any one time.

This router is also doing transcoding.

Is it normal to see high cpu like this on a voice gateway?

The difference between the cpu/interrputs is about 7%.

cpu 85%/79%

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Overall Rating: 5 (4 ratings)
paolo bevilacqua Thu, 04/16/2009 - 09:55
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Which exact IOS?

Do you have any configration slowing down the router ? like no cef, FW, NBARS etc.

Nicholas Matthews Thu, 04/16/2009 - 10:00
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What's the platform?

Do you have any applications or scripts running on the dial peers? VXML?


wilson_1234_2 Thu, 04/16/2009 - 10:33
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Thanks for the reply.


No applications running on gateway, just dial peers.

cef is enabled.

I did have an access-list that was logging the hits on the voice subnet and I took that off.

It looks like that helped some, but it still seems like the interrupts is high even when the cpu is not elevated:

CPU utilization for five seconds: 28%/22%; one minute: 30%; five minutes: 28%

There is transcoding going on from 729 to 711 to the IPCC servers.

I also am doing reverse path lookups that might not be helping the cpu:

ip verify unicast reverse-path

wilson_1234_2 Thu, 04/16/2009 - 11:27
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Thanks nic,

I went through that document prior to posting.

That is what pointed me to the acl.

The router was logging a ton of hits to the log buffer, so I am sure that was part of the problem.

I have not seen a big load yet to determine if it has made a difference, probably will see that tonight.

I took this earlier,

sh sccp connections summary

SCCP Application Service(s) Statistics Summary:

Total Conferencing Sessions: 0, Connections: 0

Total Transcoding Sessions: 29, Connections: 58

Total MTP Sessions: 34, Connections: 68

Total ALG-Phone Sessions: 0, Connections: 0

Total BRI-Phone Sessions: 0, Connections: 0

Total SCCP Sessions: 63, Connections: 126

Are the total sccp connections the number of inbound calls at the time of this snapshot?

I am trying to determine exactly what is going on from a quantity standpoint.

Is this telling me that there are 63 SIP calls with 58 of them needing transcoding?

Nicholas Matthews Thu, 04/16/2009 - 11:36
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'show cal active voice brief' may be of more use to you on this.


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