Switch User's Guide

About the CSX400
CSX400 and CSX400-DC User’s Guide 17
Routing — Routing provides a way to transfer user data from source to destination over different
LAN and WAN links using one or more network protocol formats. Routing relies on routing
address tables to determine the best path for each packet. Routing tables can be seeded (i.e.,
addresses for remote destinations are placed in the table along with network address masks and a
metric for path latency). Routing tables are also built dynamically (i.e., the location of remote
stations, hosts and networks are updated through inter-router protocols). Routing helps to increase
network capacity by localizing traffic on LAN segments and broadcasts that would result from
bridged traffic. It also provides security by isolating traffic on segmented LANs. Routing extends
the world-wide reach of networks.
CSX400 Bridging and Routing — The CSX400 can operate as a bridge, a router, or both. The
CSX400 operates as a router for network protocols that are supported when routing is enabled and
operates as a bridge when bridging is enabled. When both bridging and routing are enabled,
routing takes precedence over bridging; i.e., the CSX400 uses the protocol address information of
the packet to route the packet to the correct destination. However, if the protocol is not supported,
the CSX400 operates as a bridge and uses the MAC address information to send the packet.
Operation of the CSX400 is influenced by routing and bridging controls and filters set during
CSX400 configuration. General IP routing, and routing or bridging from specific remote routers
are controls set during the configuration process.
IEEE 802.1d Bridging — The CSX400 supports the IEEE 802.1d standard for LAN to LAN
bridging. Bridging is provided over PPP and Frame Relay as well as adjacent LAN ports. The
bridging software uses transparent bridging. When the CSX400 is configured as a bridge, the unit
bridges data packets to the destination, regardless of the network protocols used.
The CSX400 uses the Spanning Tree Algorithm to provide bridging redundancy while preventing
data loops and duplicate data. This is a self-learning bridge, i.e., the bridge builds and updates an
address table with each MAC source address and associated information when the packets are
received.
IP Routing — IP routing support provides the ability to process TCP/IP frames at the network
layer for routing. IP routing support includes the Routing Information Protocol (RIP) that allows
the exchange of routing information on a TCP/IP network. The CSX400 receives and broadcasts
RIP messages to adjacent routers and workstations.
IPX Routing — Internet Packet Exchange (IPX) routing support provides the ability to process
Novell proprietary frames at the network layer for routing. IPX routing support includes both
Routing Information Protocol (RIP) and Service Advertising Protocol (SAP) that allows the
exchange of routing information on a Novell NetWare network. The SAP provides routers and
servers containing SAP agents with a means of exchanging internetwork service information.