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New Member

2621 8-port Analog modem slow speed connection


Currently I have a 2621 with a 8 port anlog modem module. I can only get the modems to connect at 21600bps. It is using V.34, so I assume it should connect at 33600bps.

Any idea how I can't get the speed on the connection up to 31000 to 33600 ??

Here is the modem version

sh modem ver

Slot 0:MCOM Analog Integrated Modem Firmware Version 1.2.8

Source: IOS

Boot firmware: 1.1.5

MIMIC firmware: 1.3.3

Modem firmware: 2.3.17

DSP firmware: 0.0.2

Here is the config

interface Group-Async1

ip unnumbered FastEthernet1/0

ip helper-address x.160.1.235

ip helper-address x.160.1.234

encapsulation ppp

no ip mroute-cache

dialer in-band

dialer idle-timeout 10000

async mode interactive

peer default ip address dhcp

no fair-queue

compress mppc

ppp max-bad-auth 3

ppp authentication pap use-radius

group-range 1 8

line 1 8

session-timeout 60

exec-timeout 0 0

modem InOut

modem autoconfigure type mica

no exec

transport preferred none

transport output none

autoselect ppp

flowcontrol hardware


Randy McIver

New Member

Re: 2621 8-port Analog modem slow speed connection

The issue here could be two things.

One is modem compatability, as different users will be using different modems they will agree to connect at a speed compatible to both the modems. All RAS boxes will have incorporated the parameters for well known modems for other modems you may have to add the AT commands in the RAS boxes.

If you are using Cisco Access Servers maybe this URL could give you an idea about the list of compatible modems.

The other problem is with the line itself if there are more errors in the Channalised E1/T1 there could be speed lose, for this contact your Telecom provider.


Re: 2621 8-port Analog modem slow speed connection

I have had router installations with analog modem modules (e.g., NM-8AM)

and I have seen that this module is quite sensitive to grounding.

I suggest you ensure you have proper grounding as this affects modem performance.

To achieve higher connection speeds, the quality of the line really has a

very big contribution, based on experience. But you can try using the locals

(from PBX) to make sure that you can achieve 31000 and above speeds.

Also, you have the command "modem autoconfigure type mica" under

"line 1 8".

Please take note that analog modems for the 2600 series are microcom (mimic) modems. Sometimes "modem autoconfigure discovery" works well but you can try using "modem autoconfigure type microcom_mimic".

Use "show modem connect-speeds" to display connection speed statistics for all the modems running in the router.

Hope this helps.

New Member

Re: 2621 8-port Analog modem slow speed connection

Thanks for the feed back. You where dead on in both cases, the modem set was incorrect. I changed it back to modem auto discover and now works. Some times I can can connect at 31kbs and other times it connects at 28.8kps. That is with the modem in my laptop, when I try a USR it consistly connects at 31kbps. So needless to say my laptop modem is not of high quality.

Thanks for your help, take care !!

Randy M.