Point-to-point T1 with 2620XM and crossover cable

T1 is a synchronous tramsmission facility and so the "circuit" has to be timed. On a real T1 the circuit would be timed by the carrier and the router's built in DSU would synch to networkk time. in a back to bak scenario you need to provide this timing. This is done by having one of the router clock your "ciurcuit"

Use the "show controller t1" command to find out the controller designation on your router

controller t1 clock source internal

I knew that there had to be one clock source, and I entered that in the ser0/0 interface with the command "clock rate 56000". Strangely, though, it doesn't seem to show up in the output from "show running" or "show int ser0/0". I'm not sure why that is?

I'm at home now so I can't run the command you mentioned just yet, but I'll run it tomorrow morning & post the results.

TIA!

The clock rate command is used when there is a V.35 interface but not when you have a bulit-in DSU

V.35 as in if I was really using a serial cable, right? But when I'm using a T1 crossover cable the router uses it's internal DSU?

"show controller t1" shows nothing on both routers, i.e. I run the command and it doesn't give me any output; and then returns to the enable prompt.

Do I need the "service-module t1 clock source internal" command on one router, or both? I'm still having the same problems, AL and CD lights are illuminated on the WICs but Serial0/0 is still down on both routers.

Internal clocking is just done on one router; other routerwill derive clock

I think I have it up and running now, thanks! I can ping Serial0/0 on each router from the other router, without Ethernet connections plugged in.

Interestingly, "show controller T1" still does not give me any output...

"show controller t1" works with other integrated CSU/DSUs, like the VWICs. Use "show service-module s0/0" for yours.

Also keep in mind that the default timeslot size for some T1 controllers is 56kbps. That took me about 30 minutes to figure out will installing one! You set the timeslot size with

service-module t1 timeslots 1-24 speed 64

Although you've probably figured it out, one side needs to provide the clocking, and the other side receives clocking from the line.

To configure one side to provide clocking, use

service-module t1 clock source internal.

The default is to receive clocking from the line.

Great, thanks Mark! That "show service-module" command worked a treat, it gives me good information. One problem is that I didn't do a good job of crimping the crossover cable, it's easily to knock out which causes CD errors. So, I'll re-do that.

I actually used "service-module t1 timeslots all"; and according to "show service-module" it's using all 24 channels @ 64K to give me

Chris

Chris

If you are having problems with the wires not crimping in tight then you might want to check to see if you have the correct type of RJ-45 end. They come in two flavors, solid wire ends and stranded wire ends. If you look from the side of the connector and the part of the pins that contacts the wires inside is just pointed or kind of "U" shaped then it is probably for stranded wire, the type used for patch cables. If however, they have two slits or thus three fingers then they are for probably for solid wire, the type used for punch down blocks or for runs between the wiring closet, through the walls and eventually to the jack. Using one type of connector for the other type of wire will usually test the limits of your CRC counter. I tried to find a web link that shows pictures of the different types of connectors but all I could come up with was sites that talked about them and would not show them. Here is one...