Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. If you'd prefer to explore, try our test area to get started. And see here for current known issues.

New Member

not able to use 2Mbps

one telecom company is having 3640 router at one end & 1601 router at other end. for e1 connectivity they r using RAD FCD-E1 modems. in earlier configuration FCD-E1 modem has been configured for using 1 timeslot for data remaining 29 for voice. now changed configuration is changed to use total timeslots for data. modem side configuration is perfect( same configuration is working with 7206 router at one end and 1601 router at another end) the same configuration is not working with 3640 at one end & 1601 router at another end. this is the SHOW VERSION of 3640 router

Compiled Tue 07-Aug-01 19:21 by ccai

Image text-base: 0x60008950, data-base: 0x60A2A000

ROM: System Bootstrap, Version 11.1(20)AA2, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1)

MNC-RTR uptime is 4 days, 18 hours, 44 minutes

System returned to ROM by power-on

System image file is "flash:c3640-i-mz.121-5.T10"

cisco 3640 (R4700) processor (revision 0x00) with 28672K/4096K bytes of memory.

Processor board ID 26862722

R4700 CPU at 100Mhz, Implementation 33, Rev 1.0

Bridging software.

X.25 software, Version 3.0.0.

1 Ethernet/IEEE 802.3 interface(s)

1 Serial network interface(s)

16 Low-speed serial(sync/async) network interface(s)

DRAM configuration is 64 bits wide with parity disabled.

125K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

the SHOW int ser1/1 of which we are trying to configure 2mb.

Serial1/1 is up, line protocol is up

Hardware is CD2430 in sync mode


Internet address is

MTU 1500 bytes, BW 2048 Kbit, DLY 20000 usec,

reliability 255/255, txload 2/255, rxload 5/255

Encapsulation HDLC, loopback not set

Keepalive set (10 sec)

Last input 00:00:00, output 00:00:00, output hang never

Last clearing of "show interface" counters never

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: weighted fair

Output queue: 0/1000/64/0 (size/max total/threshold/drops)

Conversations 0/19/32 (active/max active/max total)

Reserved Conversations 0/0 (allocated/max allocated)

Available Bandwidth 1536 kilobits/sec

5 minute input rate 41000 bits/sec, 23 packets/sec

5 minute output rate 18000 bits/sec, 20 packets/sec

621156 packets input, 68249665 bytes, 0 no buffer

Received 48085 broadcasts, 0 runts, 1 giants, 0 throttles

284013 input errors, 0 CRC, 0 frame, 284013 overrun, 0 ignored, 0 abort

507804 packets output, 123920662 bytes, 49 underruns

49 output errors, 0 collisions, 29 interface resets

0 output buffer failures, 0 output buffers swapped out

2 carrier transitions

DCD=up DSR=up DTR=up RTS=up CTS=up

this was sh int is with 64kbps only

can u tell me what might be the problem & what is this

"Hardware is CD2430 in sync mode"

  • WAN Routing and Switching

Re: not able to use 2Mbps

There are many input errors. It may be the cable or the PTT issue. You can try to connect another router to the port and prove it.

Try to restart the modem , CSU/DSU & router to test again. Please confirm the modem is modified as full data channel.

The CD2430 is the chip of the serial interface and it is a sync. interafce.

Hope this helps.

New Member

Re: not able to use 2Mbps

those errors are came because of our trials for changing configuration & restarting of modem. the same configuration & modems working with 7206 & 1601 routers.


Re: not able to use 2Mbps

I don't remeber seeing the card say it is sync mode when it can only do sync. This may mean that this line is attached to a sync/async card.

You sh version shows you have 16 of these interfaces and 1 other serial. If you have it hooked to the card that has the 16 interfaces then that is your issue. The other serial card will depend on which type it is. If it say A/S on the board then it cannot run at high speeed.

If this is a normal high speed serial interface there is nothing to set on the router and it should work. Only other thing would be to do a show controller and verify that you have the correct cable but I assume you are using the same cable on the 7200 and 3640 so it is unlikely that is your issue.


Re: not able to use 2Mbps

IC, due to 3640 is not the same h/w of 7206. I still think is there any compatibility issue between PTT circuit / modem and the router.

Do you mean the PTT tried to replace another modem ?

New Member

Re: not able to use 2Mbps

hi jackyoung

those two modems are working with 7206 router

replaced another one also

but no result


Re: not able to use 2Mbps

Thanks for the update. In this case, there are two reasons, the serial module is failure or it does not work w/ new config.

Try to source another serial module and another 3640 to test again.

New Member

Re: not able to use 2Mbps

hi jackyoung. presently those router & modem are working with 64kbps configuration. i think there is no problem with serial port

is there any need to give clock rate?

any IOS upgrade will solve my problem?


Re: not able to use 2Mbps

The clockrate command is only required when the router act as DCE. There is no need to specify the clockrate.

I have no idea it is a bug or not. May be you can try to upgrade the IOS to a higher release. However, if it works w/ 64kbps, it should work w/ 2Mbps if the configuration is correct. This is why I suspect there is problem at the modem or the compatiblity issue.

Can you provide the config. when you enabled w/ data & voice channel at the same time ? Or do you mean you used TDM and separated equipement to terminate the voice connection ? And the router purely for data only. If it is the case, there should be no configuration change and the router will follow the clock from the PTT, so it should be the PTT problem.

Hope this helps.

New Member

Re: not able to use 2Mbps


the Modem MRO Tek RAD FCD-E1 model has that facility to divide some time slots to voice and some to data.

we are using those modems. we are having 15 pairs of modems. earlier all are in 64 kbps means 1 time slot for data remaining for voice.

now changed to use all 30 time slots to use data. this configuration is working in 9 pairs which are connected to 7206 router.

remaining 6 pairs are at another location which are connected to 3640 router. same configuration we r using at both sites

This widget could not be displayed.