- An active network device used to divide a network into
mutually isolated segments while maintaining the whole as a
single network. It connects and passes packets between two
network segments, based on their destination addresses.
- Bridges connect two local-area networks (LANs) or two
segments of the same LAN. The two LANs being connected can
be alike or dissimilar. For example, a bridge can connect an
Ethernet with a Token-Ring network. Unlike routers,
bridges are protocol-independent. They simply forward
packets without analyzing and re-routing messages.
Consequently, they're faster than routers, but also less
versatile.
- Bridges operate at the data link layer of the OSI
reference model, and are transparent to protocols and to
higher level devices like routers.
- Bridge devices are specified in the IEEE 802.1D
standard.
- Bridges are smarter than repeaters, in that they know
which computers are on which side of the bridge, so they
only allow those messages that need to get to the other side
to cross the bridge. This device improves performance on
both sides of the bridge.
- DSL modems are typically bridges.
- A bridge looks at each message on a LAN, "passing" those
known to be within the same LAN, and forwarding those known
to be on the other interconnected LAN.
- Bridges may be equipped to provide frame relay support
to the LAN devices they serve. A frame-relay-capable bridge
encapsulates LAN frames in frame relay frames and feeds
those frame relay frames to a frame relay switch for
transmission across the network. A frame-relay-capable
bridge also receives frame relay frames from the network,
strips the frame relay frame off each LAN frame, and passes
the LAN frame on to the end device.
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