1 introduction, 1 sub-interface overview, 1 introduction -2 – Nortel Networks 8000 User Manual
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5 Logical interface configuration
Nortel Secure Router 8000 Series
Configuration -WAN Access
5.1 Introduction
The section covers the following topics that you need to know before you configure logical
interfaces:
Virtual template and virtual access interface
A logical interface refers to an interface that does not physically exist, and that you create
only through manual configuration. Logical interfaces include sub-interfaces, virtual
templates, virtual Ethernet interfaces, MP-group interfaces, tunnel interfaces, loopback
interfaces and null interfaces.
CQ NOTE
•
For more details about the MP-group interface, refer to "PPP and MP Configuration."
•
For more details about the tunnel interface, refer to "GRE Configuration" in the Nortel Secure
Router 8000 Series Configuration Guide - VPN.
5.1.1 Sub-interface overview
Generally, one physical interface can possess only one main IP address.
In point-to-point connection, one main IP address can meet the application requirements.
If the link layer supports multiplexing of several connections, you may need to use
sub-interfaces in certain cases.
For example, Frame Relay (FR) supports more than one virtual connection on one physical
interface. If IP addresses of all the remote ends of the connections are in the same network
segment with this interface, one main IP address can work. However, if they are in different
network segments, one main IP address is not sufficient.
Sub-interfaces can provide multiple virtual interfaces on a single physical interface. These
virtual interfaces share the physical configuration with the physical interface, though they also
have independent link layer and network layer configuration.
The SR8000 supports sub-interfaces for a single physical interface to provide high flexibility
for user networking.
The following physical interfaces
support sub-interfaces:
•
WAN interface encapsulated
with FR
•
ATM interface
•
WAN interface encapsulated
with X.25
5-2
Nortel Networks Inc.
Issue 5.3 (30 March 2009)