CISCO HELP! With 2 cisco 2600's via T1 connection.

[Drewbad]

I am trying to get my hands on an example of a running-config of a Cisco router (preferrably a 2600) that connects to a location with another 2600 via T1 (not a PVC, etc).

This is a theory-only question for school, and must be kept simple. IP addresses and subnets can be fabricated.

Can someone cut and paste a running-config, or create a realistic example?

 

[bgroff]

hostname router1
interface ethernet 0/0
ip address 192.168.1.1 255.255.255.0
interface serial 0/0
ip address 192.168.0.1 255.255.255.252
ip route 192.168.2.0 255.255.255.0 192.168.0.2

hostname router2
interface ethernet 0/0
ip address 192.168.2.1 255.255.255.0
interface serial 0/0
ip address 192.168.0.2 255.255.255.252
ip route 192.168.1.0 255.255.255.0 192.168.0.1

There ya go... Its the bare minimum needed to get two routers talking to each other over a p-to-p serial connection and route the lans.

 

[cmetz]

Drewbad, you didn't specify the kind of T1 interface. Most folks around here will be familiar with 2600s using T1 integrated-CSU WICs.

bgroff, there's something very important missing from your configuration (assuming that we're talking the aforementioned T1 WIC modules). As this is a learning excercise, I'm going to point that out and see if your or someone else can figure out what it is before I tell you all.

 

[bgroff]

There's nothing missing if you don't need to change the service module properties. Assuming that the aforementioned T1 is coming in via a local loop provided by a telco, that config above will work.

 

[spidey07]

no shut and clock source?

 

[p0lar]

You may, or may not, need clock-source as it's assumed to be sourced from the line regardless now-a-daze. Either way, it can't hurt, but for the sake of the discussion that is the diplomatically correct answer.

If it's back-to-back serial without the T1, you'll need to specify clock rate on the DCE side; otherwise, with a circuit (of some type), service-module T1 clock source line or service-module T1 clock source internal will be needed. This depends on your provider. If you just run a crossconnect T1 cable, you'll need to specify internal. Some carriers (few lately) will let you specify it internally.

interface FastEthernet0
description * Ethernet LAN *
ip address 192.168.250.3 255.255.255.0
no ip redirects
ip nat inside
speed auto
no cdp enable
!
interface Serial0
description * 128K Fractional T1
no ip address
encapsulation frame-relay
no ip route-cache
no ip mroute-cache
no fair-queue
service-module t1 timeslots 1-2
!
interface Serial0.1 point-to-point
description * PVC to xxxxxxxxx*
ip address xxx.xxx.xxx.1 255.255.255.252
ip nat outside
no ip route-cache
no ip mroute-cache
no cdp enable
frame-relay interface-dlci 100
...etc.etc.etc...

no shut may be assumed, but a quick sh int | include line protocol will let you know one way or the other without picking through gobs of line configs. If you see [interface] is up, line protocol is down - it's probably a configuration problem on either end or a circuit problem. If you see [interface] is down, line protcol is down - the interface is probably shut down.

Here's a quick example from a 1751:

router#sh int | include line protocol
FastEthernet0 is up, line protocol is up
Loopback1 is up, line protocol is up
Loopback2 is up, line protocol is up
Loopback102 is up, line protocol is up
Loopback103 is up, line protocol is up
Loopback104 is up, line protocol is up
Loopback1000 is up, line protocol is up
Serial0 is up, line protocol is up
Serial0.1 is up, line protocol is up
Serial0.2 is up, line protocol is up
Serial0.102 is up, line protocol is up
Serial0.103 is up, line protocol is up
Serial0.104 is up, line protocol is up
Serial0.1000 is down, line protocol is down
Virtual-Access1 is up, line protocol is up
router#

Let me know if you want more [complex] examples.

 

[cmetz]

spidey07, yep. And that stuff is a gotcha that routinely nails people new to this subject.

p0lar, which LEC delivers point to point T1s in which BOTH ends are clocked by the line? I'm not sure that's even allowed / within spec.

 

[p0lar]

Oops.. a key word there point-to-point... but that's not exactly how I worded it either. (=

Note to self...and thanks for pointing that out as it may not be as obvious to some. I was thinking along the lines of a fractional T1 with multiple PVCs (probably because that's what I had under my nose at the time of writing...).