Solved: SRST support on Cisco 3845 router

anasubra_2 · ‎12-05-2008

Hi All,

We have a cisco 3845 router and we are trying to figure out,what all hardware/software components required to configure SRST on this router. Any help would be appreciated.

Thanks

Regards

Anantha Subramanian Natarajan

dprakken1 · ‎12-06-2008

Same thing - Packet Voice DSP Module (PVDM). Basically needed for terminating analog calls and transcoding between different codecs. Use the Cisco DSP calculator tool to size the PVBM needed.

Dave

View solution in original post

Nicholas Matthews · ‎12-12-2008

For an SRST router you will technically only need DSPs (PVDM) if you have an analog connection.

Generally, you will have an analog port for SRST so that phones can dial out of the system, but all you wish to have is intra-system DN reachability, you wouldn't use DSPs.

If this helps clear up the question at all.

Use the DSP calculator to figure out your DSP situation:

http://www.cisco.com/cgi-bin/Support/DSP/cisco_prodsel.pl

View solution in original post

Jonathan Schulenberg · ‎12-06-2008

SRST is a software feature of IOS. You must be on have "IP Voice" or higher to have access to it: http://cisco.com/en/US/products/sw/iosswrel/ps5460/index.html

On a 3845, up to 720 phones can fall back to it if you are using traditional SRST. If you use CME SRST which includes more functionality to the users as the CME call agent is online, you are limited to 240 phones.

The only requirements surround the appropriate level of DRAM and flash memory to run the IOS code you choose. Other hardware components like DSPs aren't a requirement of SRST directly but could be used by the CME SRST call agent to provide users supplementary features during fallback if you wanted.

http://www.cisco.com/en/US/products/sw/voicesw/ps2169/tsd_products_support_series_home.html

anasubra_2 · ‎12-06-2008

Hi J.schulenberg,

Thats really good information and so inorder to run SRST on a Cisco 3845 router,we don't need to have any DSPs(PVDM).I hope inorder to have IP voice and run SRST on the Cisco 3845 we need to have license right ?..Kindly confirm

Thank you very much

Regards

Anantha Subramanian Natarajan

mikram · ‎12-06-2008

Hi

You need PVDMs to terminate PCM calls into VOIP. You need it for codec such as G729 etc, Also you need for conference. There is DSP calculator at CCO.

Cheers

Ikram

anasubra_2 · ‎12-06-2008

Hi Ikram,

Thank you ...I have a basic doubt now,is DSP is different from PVDM ?

Thanks

Regards

Anantha Subramanian Natarajan

dprakken1 · ‎12-06-2008

Same thing - Packet Voice DSP Module (PVDM). Basically needed for terminating analog calls and transcoding between different codecs. Use the Cisco DSP calculator tool to size the PVBM needed.

Dave

anasubra_2 · ‎12-07-2008

Hi Dave,

Thank you for the clarification.

Regards

Anantha Subramanian Natarajan

dprakken1 · ‎12-06-2008

Same thing - Packet Voice DSP Module (PVDM). Basically needed for terminating analog calls and transcoding between different codecs. Use the Cisco DSP calculator tool to size the PVBM needed.

Dave

dprakken1 · ‎12-06-2008

Same thing - Packet Voice DSP Module (PVDM). Basically needed for terminating analog calls and transcoding between different codecs. Use the Cisco DSP calculator tool to size the PVBM needed.

Dave

Nicholas Matthews · ‎12-12-2008

For an SRST router you will technically only need DSPs (PVDM) if you have an analog connection.

Generally, you will have an analog port for SRST so that phones can dial out of the system, but all you wish to have is intra-system DN reachability, you wouldn't use DSPs.

If this helps clear up the question at all.

Use the DSP calculator to figure out your DSP situation:

http://www.cisco.com/cgi-bin/Support/DSP/cisco_prodsel.pl

anasubra_2 · ‎12-12-2008

Hi nicmatth,

The explanation clarifies the question. Thank you very much

Regards

Anantha Subramanian Natarajan