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Community Member

How to connect two routers back to back

I have two routers cisco 1720 with 56/64 DSU/CSU WIC and t1 dsu/csu wic and a cisco 1602 with t1 dsu/csu wic . I wanted to connect them back to back for testing purposes. Itried using a crossover cable and I couldn't get a link for both of them is there something that I'm missing or doing wrong in here? I tried to search for this and the only thing that keeps on popping up was to use a Serial Cable which both routers don't have serial inputs. Thank you in advance for advices and answers.

4 REPLIES
Community Member

Re: How to connect two routers back to back

you try out one the router with clockrate command, i mean one route configure as DCE and other is DTE

2) Check keepalive timing

3) check encapulation

4) otherwise also tried tested cross cable

Re: How to connect two routers back to back

make sure you are having correct cross cable for T1...for T1 its configuration is

1 <--->4

2 <--->5

4 <--->1

5 <--->2

check it out for this...

hope this will help you

rate this post if it helps

regards

Devang

Gold

Re: How to connect two routers back to back

First make sure you have a correct cross cable. I assume you are attempting to connect a wic-1dsu-56k4 and a wic-1dsu-t1.

These use different pinout. A t1 uses 1,2,4,5 a 56/64 uses 1,2,7,8. I have not made a cable like this but I suspect you should be able to use 1-7,2-8,4-1,5-2 where the first number in the pair is the t1 end of the cable.

Now you must reconfigure also the t1 card to run as a fractional using only the first channel.

Community Member

Re: How to connect two routers back to back

To beat a dead horse:

A T-1 uses cable pairs 1-2 and 4-5. So, your cable would cross these two pairs.

Pin 1 on one side goes to Pin 4 on the other end. Pin 2 goes to 5, 4 goes to 1,

and 5 goes to 2. All you need to do is have one side provide clocking on the line,

just as a serial interface would.

1 orange/white

2 orange

3 white/green

4 blue

5 white/blue

6 green

7 white/br or bl

8 br or bl

1 blue

2 white/blue

3 white/green

4 orange/white

5 orange

6 green

7 white/br or bl

8 br or bl

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