Cisco IP SLA: c5510 or c549 DSP

Unanswered Question
Dec 24th, 2008

Hi: I am trying to configure Cisco IP SLA (SAA) on some routers. Cisco docs say the source router must have a network module with a c5510 or c549 DSP. Is this like an additional card that goes into the router? What does this card do in addition to allowing me to enable the Cisco IP SLA?



  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Nicholas Matthews Wed, 12/24/2008 - 07:10

The PVDM is a DSP. The DSP turns RTP packets into analog audio. It is the part of the router that is responsible for creating voice packets.

You can do a 'show diag | i FRU' to see if you have any DSPs. NM-HDVs will have c549s, and other modules have the PVDM2-X.

You will only need PVDMs for the voice SLA, you should be able to do UDP echoes, pings, and the likes without DSPs.



emorgan Wed, 01/21/2009 - 10:25

Hi, I have just configured a voip-rtp SLA on a 2821 with 12.4(20)T. I have FXO and PRI ports for testing purposes.

If i use say source-port 0/2/0, it assigns a 5510 DSP channel to this test.

What happens if a call comes in that FXO port while the test is being performed? Do I need to dedicate a port for SLA?

What about if I have a PRI instead. Do I need to reserve something like the last PRI channel for SLA so there are no conflicts with incoming/outgoing calls? (like source-port 0/3/0:22)

Last question... unlike udp-jitter, the CLI will not accept DSCP tags ("tos 184" for dscp EF). What is the default dscp and can it be changed?

My preliminary config:

ip sla 3099

voip rtp x.x.x.x source-voice-port 0/2/3 codec g729a duration 20 advantage-factor 0

frequency 180

history hours-of-statistics-kept 4

ip sla schedule 3099 life forever start-time now



emorgan Wed, 01/21/2009 - 10:35

Correction, I am running 12.4(15)T4. Will test again on 12.4(20)T soon.

Nicholas Matthews Wed, 01/21/2009 - 11:20

I'm not familiar with the functionality using the voice-port rather than IP address.

However, both of these issues (DSP allocation/DSCP marking) do not exist if you use a source IP address instead of voice port.

The command reference isn't particularly helpful either. I would start by using the IP source, and use the voice port if there is something about the function of the IP address that doesn't suit your requirements.




This Discussion