Cabletron Systems CyberSWITCH CSX400 Installation Manual

Also see for CyberSWITCH CSX400: Setup guide Configuration guide User guide User guide User guide

Contents

CSX400 Firmware SupportCyberSWITCH CSX400 and CSX400-DC Installation Guide2-15Bridging and RoutingBridging — Bridging connects two or more separate networks together. The bridge examines aportion of each network frame called the header. This header contains control information for theframe. The bridge compares the destination address of the frame to a table of source addresses(bridges dynamically learn the physical location of devices by logging the source addresses ofeach frame and the bridge port the frame was received on in the source address table). Intransparent bridging, the decision to forward the frame is based on this comparison. If the addressindicates that the sending station and the destination station are on the same side of the bridge, theframe is not forwarded across the bridge. If the addresses do not indicate that, the bridge forwardsthe broadcast frame across the bridge to the other network(s).Bridging allows frames to be sent to all destinations regardless of the network protocols used. Italso allows protocols that cannot be routed (such as NETBIOS) to be forwarded, and optimizesinternetwork capacity by localizing traffic on LAN segments. A bridge extends the physical reachof networks beyond the limits of each LAN segment. Filters can be used to increase networksecurity in bridged networks, and restrict message forwarding by using user-built addresstables (non-transparent bridging).Routing — 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.