Weird CPU usage ?

[TrickTrick]

Hello,

I have some issues using an ISR 4321 as a voice gateway, when I hang off the IP phone, I can hear the caller but after like 7 to 10 seconds, during which nothing is heard at all for both ends, I thought it might be a high CPU usage which makes the router slow to process the call, so I issued "show processes cpu sorted" and "Show processes cpu history", in the first the cpu seems like to be not used almost (0%, 1%), I'm not sure of the second one though because there's no stars (*) and no (#) but looks like the CPU is totally fine, can you please confirm if my read is correct?

CPU utilization for five seconds: 1%/0%; one minute: 0%; five minutes: 0%

sh processes cpu history

22222
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per second (last 60 seconds)

121111111111111112111121111111111111111111111112111111111111
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6
0 5 0 5 0 5 0 5 0 5 0
CPU% per minute (last 60 minutes)
* = maximum CPU% # = average CPU%

222222222222222222222222222222222222222222222222222222222322222222222222
100
90
80
70
60
50
40
30
20
10
0....5....1....1....2....2....3....3....4....4....5....5....6....6....7..
0 5 0 5 0 5 0 5 0 5 0 5 0
CPU% per hour (last 72 hours)
* = maximum CPU% # = average CPU%

[Elliot Dierksen]

Do you have an explicit binding for an interface for H.323? Something like this:

interface Loopback1
 ip address 10.65.255.21 255.255.255.255
 h323-gateway voip interface
 h323-gateway voip bind srcaddr 10.65.255.21
!

Are you using slow start (the default) or fast start? Fast start would look something like this.

voice class h323 10
  h225 timeout tcp establish 2
  call start fast
!
dial-peer voice 100 voip
 destination-pattern 1...
 session target ipv4:10.1.100.64
 voice-class codec 10
 voice-class h323 10
 dtmf-relay h245-alphanumeric
 no vad
!

If you don't have an explicit interface binding, I would add that. Also, is there NAT involved? The H.245 negotiation allows the side with the higher IP (I think) to start the codec negotiation. If NAT causes both sides to think they should be passive, that can be a problem. Mainly I would look at the firewall logs right at the start of a call and see if there are any "Deny" messages.

[TrickTrick]

Hello Elliot,

There's no manual interface binding for H.323, a standard configuration nothing fancy, no fast start neither 

What's the benefit of binding a loopback to H323 ? if it's to avoid using the physical interface I'm already using vlan interfaces only since we are using a switch module in the ISR and a trunk link between ISR and the firewall and There's no NAT between sites

[Elliot Dierksen]

I would only bind to a loopback interface if you had multiple paths to your call control (or wherever you are sending the H.323 calls). Otherwise, bind it a physical (like an ethernet interface). I almost never see H.323 any more, but I do remember that I would always bind H.323 to a specific interface to be sure the other side saw a predictable IP for the control traffic. I would say pick one of your VLAN interfaces and use that.