This document explains how to bring up a subrate trunk in a lab
In typical installations of subrate trunks, the trunk clocking is
provided by the Telco. In order to use subrate trunks in a lab environment, you
must provide a clock on the interface.
A subrate trunk (or packet line) is a communication link between two
IPX nodes or IGX nodes, or both. The sub refers to the rate being less than T1
or E1 rate. A subrate trunk can not talk to fractional T1/E1 packet lines
because they use different line synchronization mechanisms. This means that
they can sync up one day, but not the next.
The physical interface can be V.11/X.21, V.35, or RS-449 interfaces.
The requirement is to emulate real-world configurations in a lab
A subrate trunk requires clock be provided on each interface. In
addition, the TX and RX data signals must be crossed between the trunk cards.
This crossover can be accomplished using a crossover cable or a device that
emulates a Telco subrate interface. With a cross-over cable, a clock must be
provided to the interfaces because the subrate trunk card is a data terminal
equipment (DTE) interface and does not supply clock.
This document is not restricted to specific software and hardware
Technical Tips Conventions for more information on document
The data rate of the subrate trunk must be a value supported by the
IPX/IGX. Supported rates are:
Complete these steps:
Add a local connection between two DCE ports on a single SDP (or
HDM) using the V.35 or RS-449 interface matching the subrate trunk cards. The
connection is configured with DCE interfaces on both ports. The data rate of
the connection must match the rate of the trunk.
Connect a straight-through cable from one SDP/HDM port to one of
the subrate trunk connectors.
Connect another straight-through V.35 or RS-449 cable from the
other SDP/HDM port to the other subrate trunk connector.
Configure the subrate PLN/Trunk for the rate of the SDP/HDM local
Add the subrate PLN/Trunk.
The subrate trunk uses the SDP/HDM card as the Telco. The SDP/HDM card
provides clocking and the mechanism for crossing the transmit and receive data