Sometimes you need a quick and easy way to test a T1 connection on a piece of equipment. For example, you want to make sure that the T1 WIC on your router is working.
To construct a loopback plug, simply take a single RJ45 plug and connect pin 1 to 4 and pin 2 to 5.
In setting up my home lab, one thing that I needed to do was communicate between my routers using the T1 WICs. For the physical cable connection it is necessary to use a T1 Crossover cable. This is really simple to construct. Using standard twisted pair cable and RJ45 ends, make the following connections: pin 1 to 4, 2 to 5, 4 to 1 and 5 to 2. Below is a diagram:
I have a couple of routers as part of my home lab that I am using for my Cisco certification studies. One thing that I wanted to do was connect two routers together via their T1 WICs. There are two things you need to do:
In another post I will put the details of making a T1 crossover cable, here is a simple example of the configuration you need to apply to each routers’ T1 serial interface.
**apply this to router #1**
ip address 192.168.1.1 255.255.255.248
encapsulation ppp
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24 speed 64
service-module t1 framing esf
service-module t1 linecode b8zs
no shut
**apply this to router #2**
ip address 192.168.1.2 255.255.255.248
encapsulation ppp
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24 speed 64
service-module t1 framing esf
service-module t1 linecode b8zs
no shut