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BT LES 100 and Cisco 2600 Configuration


Had some difficulties making a BT Megastream circuit work. The circuit was required to connect two distant sites at a speed of 4Mb/s. BT terminate the circuit at each end at a card called a LES 100 which provides an ethernet RJ45 connection. Essentially it is like having a patch cable between your sites. You should be able to install a device at the remote end and operate it as if you were on the local network.
Initially I could not get anything to work over the connection. BT were certain that the line was installed correctly and was fully operational. It was only after the issue being raised to their second level support team that the problem was resolved.
Here's what was done.
  1. BT fixed the configuration of the circuit to ensure that line speed and duplex mode were set correcly ie. the same at both ends of the circuit.
  2. I set the interfaces on the router to :-
    1. speed 100
    2. duplex full
It seems that the LES 100 card does not like talking to devices that autonegotiate the speed and duplex settings. It would be a good idea if BT told you this before you waste hours trying different bits of kit and configurations.

Definitions

  1. BT - British Telecom.
  2. LES - Lan Extension Service

Keywords

BT LES 100 LES100 Cisco 2600 Megastream config configuration

Slash Notation


Sometimes you have to specify a subnet mask in slash notation
i.e network 172.16.0.0 subnet mask 255.255.0.0 can be written in slash notation as 172.16.0.0/16
Subnet mask Slash Notation
0.0.0.0/0
255.0.0.0/8
255.255.0.0/16
255.255.255.0/24
255.255.255.192/26
255.255.255.240/28
255.255.255.255/32

Keywords

sub net mask subnet subnetmask