About the CSX400CSX400 and CSX400-DC User’s Guide 17Routing — Routing provides a way to transfer user data from source to destination over differentLAN and WAN links using one or more network protocol formats. Routing relies on routingaddress 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 ametric for path latency). Routing tables are also built dynamically (i.e., the location of remotestations, hosts and networks are updated through inter-router protocols). Routing helps to increasenetwork capacity by localizing traffic on LAN segments and broadcasts that would result frombridged traffic. It also provides security by isolating traffic on segmented LANs. Routing extendsthe world-wide reach of networks.CSX400 Bridging and Routing — The CSX400 can operate as a bridge, a router, or both. TheCSX400 operates as a router for network protocols that are supported when routing is enabled andoperates 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 ofthe 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 duringCSX400 configuration. General IP routing, and routing or bridging from specific remote routersare controls set during the configuration process.IEEE 802.1d Bridging — The CSX400 supports the IEEE 802.1d standard for LAN to LANbridging. Bridging is provided over PPP and Frame Relay as well as adjacent LAN ports. Thebridging software uses transparent bridging. When the CSX400 is configured as a bridge, the unitbridges data packets to the destination, regardless of the network protocols used.The CSX400 uses the Spanning Tree Algorithm to provide bridging redundancy while preventingdata loops and duplicate data. This is a self-learning bridge, i.e., the bridge builds and updates anaddress table with each MAC source address and associated information when the packets arereceived.IP Routing — IP routing support provides the ability to process TCP/IP frames at the networklayer for routing. IP routing support includes the Routing Information Protocol (RIP) that allowsthe exchange of routing information on a TCP/IP network. The CSX400 receives and broadcastsRIP messages to adjacent routers and workstations.IPX Routing — Internet Packet Exchange (IPX) routing support provides the ability to processNovell proprietary frames at the network layer for routing. IPX routing support includes bothRouting Information Protocol (RIP) and Service Advertising Protocol (SAP) that allows theexchange of routing information on a Novell NetWare network. The SAP provides routers andservers containing SAP agents with a means of exchanging internetwork service information.
