Circuit Turn-up

Circuit turn-up is the process of making your connection active. This process varies slightly depending on whether your link is via frame relay or a dedicated line, but in general it goes something like this.

The data line service provider calls the person listed as technical POC (Point Of Contact) at the company which placed the circuit order. The telco rep asks if all the equipment is plugged in and turned on, and whether the data line has been connected to the network termination device, usually the CSU/DSU. If it is, the telco rep will begin testing the line. If it is a frame relay connection, the telco rep looks for LMI (Local Managment Information) packets coming from the router at the remote end. If the rep sees LMI, then it is probably possible to "ping" the remote end. If you can ping the remote end, the circuit is "up", and the billing starts right along with the data flow.

If no LMI is present, there are a number of things that could be wrong. These include the following:

The CSU/DSU is not configured correctly
The router does not have LMI enabled
The CSU/DSU is not plugged in to the Hi-Cap jack
The CSU/DSU is defective
The line between the dmarc and the local telco switch is installed incorrectly
There is a problem with a telco switch along the circuit path

If the Telco sees LMI but you cannot ping the end-points, the following could be responsible:

The router at the remote end has the wrong (or no) routes configured
The router at the local end has the wrong (or no) routes configured
The router at the remote end is defective

You can ping the end-points, but the remote end cannot get out to the Internet:

The router upstream from you, at your Internet Access Provider, does not have the correct routes installed.

You can ping the IP addresses of machines on the remote network, but not their host names

This is a DNS problem. Make sure there is forward and reverse DNS data available and that the serial numbers of all related DNS files have been updated, and the named daemon has been restarted (use "kill -HUP process-id" to restart the daemon).

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Creation Date: Saturday, October 19, 1996
Last Modified: Sunday, December 14, 1996
Copyright © Ray Smith, 1996