How to Loopback Test

amb1s1

Hi, I having a lots of problem with our service provider where they are just keep saying that the problme is in our end and we going in a back and for discussion. Now, I'm just couple of months of experience and I'm not familiar with the loopback test. I would like to know how to do it, so I can have something to prove that there is nothing on our end.
This is our interface config:

interface Serial0/0/0
description Serial0_0_0_VB_00001_256K_Port_72_RTR
bandwidth 256
no ip address
encapsulation frame-relay IETF
ip route-cache flow
no ip mroute-cache
fair-queue
!
interface Serial0/0/0.35 point-to-point
bandwidth 256
ip address 66.149.87.234 255.255.255.252
snmp trap link-status
frame-relay interface-dlci 35
!
!
What I do now is, I have the NOC check for Power on Equipment, Reset Equiment, check configurations. I know that this is something I have to learn. Thanks

Stotic

Google "how to create a loopback cable". If you can get the carrier on the line, a smart thing to do is put a loop on your Smartjack facing the carrier. If they see the circuit looped then the carrier is in the clear. Another good test is to plug the loopback cable at the end of the rj45 that plugs into Smartjack to verify internal cabling. If you do a "show int se0/0/0" you should see "(looped)" at the top.

amb1s1

Stotic wrote: »

Google "how to create a loopback cable". If you can get the carrier on the line, a smart thing to do is put a loop on your Smartjack facing the carrier. If they see the circuit looped then the carrier is in the clear. Another good test is to plug the loopback cable at the end of the rj45 that plugs into Smartjack to verify internal cabling. If you do a "show int se0/0/0" you should see "(looped)" at the top.

What about if I'm not in the location? Can I do remote loopback test?

vinbuck

If you have already cleared your local loopback tests and have the output to prove it's not you, then you can request that the telco perform either a remote line loopback or a remote payload loopback - usually this must be coordinated with the carrier and they will be more likely to do it if you have hard data you can e-mail to prove it's not your side of the link. be weary of accepting what the carrier tells you at face value if you have evidence that points to the contrary. On more than one occasion, I've had a carrier tell me they could loop to the CSU/DSU on my router when I had nothing plugged into the smartjack.

This is a pretty standard command set and the carrier may not use Cisco gear, but here is the Cisco definition of it.

Cisco IOS Release 12.0 Interface Command Reference - Interface Commands (interface - loopback remote) [Cisco IOS Software Releases 12.0 Mainline] - Cisco Systems

*BB*

You can always ask the carrier to test through the smartjack. Remote testing does not do this. They would have to dispatch and connect their tester to the smartjack. Ive seen plenty of times where they could loop the front portion of the smartjack and call the circuit good. We get them to dispatch and test through, and they find that the problem was on the backside of the smartjack where you connect your equipment.

vinbuck

Do you manage the routers on both sides of the link or do you only manage one side of it?

sides14

Definitely disconnect from the NIU, plug in a loop plug and have the provider test the path without looping up the NIU. If you are using a CSU, many CSUs have internal loopback capabilites that will allow you to test your equipment connections.

amb1s1

MississippiGuardsman wrote: »

Do you manage the routers on both sides of the link or do you only manage one side of it?

I only manage, the router on my side.