Cisco 3640 Serial Interface for FrameRelay

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Mar 13th, 2009
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I want to run/setup FrameRelay in my home lab. I've the following routers,

3640,2611,2501 & 1700.

I want 3640 to be my Frameswitch, however it doesn't have Serial interface, so i wanted to buy it & that's where i got confused. Following are the serial modules available for 36xx series. which one should I go for?

NM-16A - 16 port high-density async network module

NM-32A - 32 port high-density async network module

NM-4T - Four-port serial network module.

NM-4A/S - Four-port async/sync serial network module.

I believe for FrameRelay we can use any router with 2 or more serial interfaces (for more connectivity). Im new, if its wrong, correct me please...



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Giuseppe Larosa Sat, 03/14/2009 - 06:30
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Hello Sylvester,

synchronous serial are needed so you need one of the following:

NM-4T - Four-port serial network module.

NM-4A/S - Four-port async/sync serial network module.

be aware that A/S cannot have a speed grater then 128 kbps when used in sync mode

A/S can be used also to configure a terminal server when used as async.

Hope to help


framedrelay Mon, 03/16/2009 - 18:04
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Thanks Giuseppe; Much appreciated. Its clear :)

I've one another Question, (apologies if stupid question :) )

Everywhere (lab) i've seen people using DCE-DTE cables, while DCE end connecting to frame switch; this is Lab..

Now real world, how the connection will be to the frameswitch? It will be with the service provider, how the connection to the customer permises will be?..

On my router, apart from Serial, I've vwic 2mft-t1 interface as well, whether this can be used?

As I mentioned, I am new to this, help will be much appreciated.


framedrelay Mon, 03/16/2009 - 20:32
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I've following Serial Interface on my Cisco routers.

1/ Cisco 2621 -

a) Module - VWIC-2MFT-T1-DI

b) Fractional T1 - DSU/CSU

2/ Cisco 3640 -

a) NM-4T - Four-port serial network module. (as Giuseppe said, I ordered that module).

b)Module - VWIC-2MFT-T1-DI

3/ Cisco 2501

a) Two Serial ports (RS232 type)

4/ Cisco 1700

a) Fractional T1 - DSU/CSU

I want to make my 3640 as FrameSwtich, so can i connect DCE-DTE (RS232) cable to 2501; & RJ 45 type cable to 1700 and 2611 ? Will that work? Bottom line is I want connectivity to all 3 routers from 3640, for testing frame relay.

Thanks a lot,


prakkdangc Wed, 03/18/2009 - 18:43
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So .. the VWIC in the 3640 can connect to the 1700 and the 2621 with T1 crossover cables (1,2 -> 3,5) and the NM-4T will need the 60 pin D crossover DCE-DTE cables. That leaves on port available on the 2621 .. unless your configuring Drop and Insert on the VWIC, then the additonal port will be necessary. Cool. Looks good.



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