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Chapter 1: Introduction
1-2
Router Option Module User Manual 61200350L1-1
Network Address Translation (NAT)
Single networks can connect to the Internet with this function. The
Router Option Module translates outgoing IP packets over the T1 to
the IP router at the Internet Service Provider. Popular Internet ap-
plications are supported.
PPP or Frame Relay
The layer 2 protocol used to transfer packets can be PPP or Frame
Relay (RFC 1490). PPP allows a point-to-point connection, whereas
Frame Relay can provide up to ten permanent virtual circuits.
Routing and Bridging with the Router
Option Module
The Router Option Module is a Router and Transparent Learning
Bridge. Its features can be easily configured and used, once several
basic concepts are understood.
Factory Default
The Router Option Module comes from the factory configured for
MAC Bridging, IP routing, and IPX routing with no filters or con-
nection information defined. An IP address of 10.0.0.1 with a net-
work mask of 255.255.255.0 is preloaded. The factory default layer 2
configuration is PPP, which provides the least amount of reconfigu-
ration due to its negotiation-oriented nature.
Bridging
In Bridge Mode, the Router Option Module can be used to connect
two LAN segments. In this mode, all protocols are supported be-
cause they are transported across the T1 link at the MAC layer. The
Spanning Tree Algorithm can be used to guarantee a loop-free to-
pology. MAC- save addresses are “learned” by each Router Option
Module to prevent non-WAN packets from being bridged.
IP Routing
The Router Option Module operates as an IP router when the Con-
figuration/IP/IP Router/Mode option is configured to On. In PPP
mode, the Router Option Module uses an IP unnumbered WAN in-