You'll never learn THIS in GNS

A colleague building his home lab mentioned he couldn't get his serial port (T1 WIC card) interconnects up. I had the same issues back when I built my lab, but couldn't remember the fix. I checked my lab configs and nothing special is configured on the serial ports.

I've got a serial connection between R1 and R2's ser0/0 ports

R1#show run int ser0/0

interface Serial0/0

description link to R2

ip address 10.1.1.6 255.255.255.252

end

R2#show run int se0/0

interface Serial0/0

description link to R1

ip address 10.1.1.5 255.255.255.252

end

R1#ping 10.1.1.5

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.5, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/4 ms

R2#ping 10.1.1.6

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.1.1.6, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/4 ms

I remember having a tough time getting this connection up/up, so I checked the cable for the hell of it, assuming it was a crossover.

Now I'm thinking, wtf.  That's not a crossover.

It started coming back to me, the struggle I had with this. I remember the ints were up/down and nothing I did changed that.  Tried clocking, messing with speed/duplex/bouncing interfaces and anything else I could think of.  Eventually I gave up and put it down for a while.

Then, I found this:

Sumbitch.  Not a straight, or a crossover or even a rollover.

A T1 connection has its own damn pin out.

I made that cable and it's been up/up ever since.

So there ya go, another Layer 1 issue.

You'll NEVER learn THAT in gns :)