A network bridge connects multiple
network segments (network domains) at the
data link layer. It is sometimes called a
network switch, and it works by using
bridging. Traffic from one network is forwarded through it to another
network. The bridge simply does what its name entails, by connecting two
from adjacent networks.
is a similar device that connects network segments at the
physical layer. An
Ethernet hub is a type of repeater.
Bridging takes place at the data link layer of the OSI model. Therefore a
bridge can only read the
header which provides the
address of the source and destination address. When a broadcast packet
transmitted, the bridge floods all the ports with the broadcast packets.
use two methods to resolve the network segment that a MAC address belongs
- Transparent Bridging . This method uses a forwarding database to send
packets across network segments. The forwarding database is initially
and entries in the database are built as the bridge receives packets. If
address entry is not found in the forwarding table, the packet is flooded
all ports of the bridge which sends the packet to all segments except the
source address. This type of bridging is common in Ethernet networks. To
frame looping, a spanning tree is created from the network graph and
not present in it are kept inactive; they can become active again if
bridge stops working.
- Source route bridging . This method is used in
Ring networks. See below.
In Ethernets, the term "bridge" formally means a device that
according to the
802.1D standard - this is most often referred to as a
network switch in marketing literature.
More about Network bridges can be found here.
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