Yes you can. There are a couple of ways to do this. With two routers you can have them back-to-back with or without a T1 link. One way is purchase the special cable that allows you to connect the routers together. A second way is to get a serial to V.35 DTE and DCE cable set and connects the two V.35 connectors together. A third way is to make a T1 back-to-back cable and then connect the two routers through the DSU/CSUs.
What are the Cisco cables for DTE to DCE back to back?
CAB-V35MT and CAB-V35FC (Cisco 2500 or other high density serial connectors)
If you are using a T1-WIC card, don't forget the following command:
! interface s0 service-module t1 timeslots 1-24 !
What pins do I need to connect for a T1 loopback cable?
Using a RJ45 and looking from the connector side up, with the cable end point towards yourself, count from left to right. Pin 1 to 5 Pin 2 to 4 Pin 4 to 2 Pin 5 to 1
A useful troubleshooting aid is to make a single loopback connector, pins 1 -5 and 2-4 This will let you test the serial interface to the T1 interface termination.
This will let you bring up the T1 interface and test just as if you had a Telco pull point-to-point circuit.
Can I make a 56K back-to-back cable?
Sure, construct the 56K crossover (back to back) cable by using pins 1-7, 2-8, 7-1, 8-1
Any other things I need to know about a 56K back to back?
You cannot use a clock rate of 64, cannot use switched-56 or use the clock rate of auto on either side
Can I emulate a frame relay connection without using the phone company?
Absolutely.. you need a third Cisco router with TWO serial ports. You also need two back-to-back cables or 2 DTE and 2 DCE cables. The third router is configured using the command:
! Cisco dual serial port router ! frame-relay switching ; enable frame switch ! interface serial 0/0 no ip address encapsulation frame-relay ; sets encapsulation to frame relay clockrate 38400 ; gens clock rate of 38400 to DTE frame-relay lmi-type ansi ; sets ANSI type frame-relay intf-type dce ; sets DCE or DTE frame-relay route 100 interface serial 0/1 101 ; defines the PVC between ports S0/0 and S0/1 ! interface serial 0/1 no ip address encapsulation frame-relay clockrate 38400 frame-relay lmi-type ansi frame-relay intf-type dce frame-relay route 101 interface serial 0/0 100
To connect two HSSI ports back to back, use a null modem cable, part number [colorred]92-0727-01 and use the command: hssi internal-clock to turn on the internal clocking. Don't forget to turn it off when you remove the back to back cable.