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Walkthrough Wednesdays

2801 Routers Voice capable?

I'm very new to VoIP and have been researching the implementation of VoIP on my network. I have a bunch of questions however I will limit it to a couple. I have 17 locations all with Cisco 2801 routers (IOS v12.4(c1), 61MB flash, 128mb memory) and it appears that IP is the only available feature on my device. Is this okay for Voice? Or do I need to upgrade the IOS or hardware?

Cisco Employee


the 2801 series router is capable of voice depending on the hardware installed. What exactly do you plan to implement with the 2801s? 12.4(c1) sounds like the boot loader version. If it is the actual IOS version then I would definitely advise upgrading IOS to a newer and supported version. You may also need to change the feature set, identified by either the top line of the show version  output or the filename, from ipbase to either ipvoice or higher. Last I checked the Voice Business Unit recommends 12.4(15)T for any new voice deployments. I would use that as a starting point and upgrade based on specific feature needs.

The hardware may need to be upgraded depending on the purpose. If FXO/FXO or voice T1s are required then DSPs, in the form of PVDM2-xx, will need to be installed.



Thanks for the quick and informative reply Felipe.

We are looking at a new IP phone system, likley Cisco, we currently have a DS3 at HQ that is fragmented out to our 17 locations, single T1 at small locaitons and bonded T1s at larger locations. We ordered 2/24 channel PRI's for the phone system, our primary goal is to simply get IP phones in, nothing really complex at this time. I also need to setup VLANs and QOS which is also new to me. However, I need to figure out if my equipment is capable or if I need to upgrade.

Our support license has lappsed, so would it be recommended to simply renew and update the IOS or should I consider new/better routers?

The Show Version returns:

Cisco IOS Software, 2801 Software (C2801-IPBASE-M), Version 12.4(1c), RELEASE SO                                                                             FTWARE (fc1)
Technical Support:
Copyright (c) 1986-2005 by Cisco Systems, Inc.
Compiled Wed 26-Oct-05 08:42 by evmiller

ROM: System Bootstrap, Version 12.3(8r)T8, RELEASE SOFTWARE (fc1)

GHM2801 uptime is 1 day, 50 minutes
System returned to ROM by power-on
System image file is "flash:c2801-ipbase-mz.124-1c.bin"

Cisco 2801 (revision 5.0) with 114688K/16384K bytes of memory.
Processor board ID FHK0952F29R
2 FastEthernet interfaces
1 Serial interface
1 Channelized T1/PRI port
DRAM configuration is 64 bits wide with parity disabled.
191K bytes of NVRAM.
62720K bytes of ATA CompactFlash (Read/Write)

Configuration register is 0x2102

Regarding Hardware, I'm not clear on what you mean by RE: If FXO/FXO or voice T1s are required then DSPs, in the form of PVDM2-xx, will need to be installed.

Thanks again for your assistance.



I think I answered my own question on the FXO/FXO, we are using voice T1s and so I will need to ensure we have DSPs in the form of PVDM2-xx.



You'll definitely need to upgrade both the version and feature set to support voice. the IPbase feature set currently on the router does not support any voice functionality.  As you stated, DSPs will be required as well as a VWIC2-xMFT-T1/E1  to terminate the ISDN PRI circuits.

The amount of flash/RAM on the 2801 will limit which versions of IOS and which features sets will be supported. The 2801 should be powerful enough to handle 2 PRIs worth of voice traffic. It would be best to discuss this with your Cisco partner or account team to verify performance numbers before moving forward.




Thank you again... Yes, I will work with our Cisco partner on this, at least now I have a better understanding of what I may need to purchase/upgrade to move forward on the project.



One more thing came to mind on this. Correct me if I'm wrong, but I should only need one (maybe two) router at HQ that the PRIs come into? Becasue from there, it would then all be IP based so the 2801s at each location won't need to be touched as they will simply handle routing on an IP basis?


Correct, only the routers that terminate voice need to support voice.



If he's planning to have SRST at any of his remote sites I believe he'll need IP Voice at a minimum.



Yes, we are planning on a Unified SRST, so you are saying that each of my branch office routers will need to be IP Voice or just the SRST site?


If you are planning on SRST then the local 2800 (at remo

te site) will need to have a version of IOS that is supported for the version

of CUCM you are running.  This can be verified in the C

UCM compatibilty tables.  One other thing, for SRST you will need a chassis that supports the number of phones that will register to it.  The 2801 allows only 25 phones to register in SRST.


Each router that you want to provide SRST functionality will have to have the appropriate feature set and again, I believe this is IP Voice.  Frank was correct in pointing out that you need to make sure you size your gateways appropriately as well, but these are all issues your Cisco partner should be taking into account.


Thank you Frank and Philip,

I meet with our local Cisco partner this week and the information you've provided me will help me ask appropriate questions.

Thanks again.


Good luck and let us know how it turns out!

Also, please rate helpful posts.



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