T1 Phsyical Layer Question

[z8z]

I recently saw my first T1 installation, which is carrier I know nothing about, and I noticed there was a 56Kbps modem attached to a Cisco ISR via a serial cable which I assume was RS-232.

I'm just wondering what the function of 56Kbps modem is in a T1 setup and what a good starting point would be for learning more.

Thanks HF.

 

[BinarySynapse]

Honestly, wikipedia is a good place to start on this one.

https://en.wikipedia.org/wiki/T-carrier

 

[Sinclair]

Chances are the 56K was a backup method for getting into the router if the T1 is down. We used to do something similar for our remote sites when I worked for a local datacenter. If the main link was down, we could still get into the routers and see why and troubleshoot.

 

[deaedius]

Yes the 56k Modem is just that a modem connection to access the router. We also did similar for remotely accessing equipment that we lost access to.

 

[/usr/home]

This is normal. Pretty much any decent provider does this for dedicated service. Whether that be copper (T1,T3,etc) or fiber.

 

[z8z]

Thanks ryan, sinclair, deaedius, usr.

I did have a feeling that the role of the modem had something to do with redundancy.

 

[Nicklebon]

The general term used is "out of band management." The redundancy is purely for management of the router. We would typically combine a modem with a terminal sever, or better a combo device, to manage routers, firewalls and switches on the customer prem.

 

[hawk82]

Sounds like an AT&T circuit install. That's the SOP for them.

 

[JeffBlair]

I know with my company most of our customers have some sort of dial backup. I know of one customer right off that has a Cisco router connected connected to a old dial-up modem. And, like other people said, it's for when the main connection goes down so the site can still function.
We also do a lot of wireless backup connections that do the same thing.

 

[z8z]

Thanks guys, lot of good keywords that are helping my search for knowledge.