3com 3C840 Guía Del Usuario
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C
HAPTER
1: O
VERVIEW
What is a BRouter?
A BRouter is an interface between two networks, functioning as a router
and/or a bridge. A router finds the best route between networks and
provides network management capabilities. The OfficeConnect Remote
840 is a protocol independent router that does not rely on the
workstations on a LAN for routing information, such as the destination
location and best route.
and/or a bridge. A router finds the best route between networks and
provides network management capabilities. The OfficeConnect Remote
840 is a protocol independent router that does not rely on the
workstations on a LAN for routing information, such as the destination
location and best route.
Routing vs. Bridging
Routers forward packets based on network-level addresses. Bridges
forward packets based on hardware-level, or media access control (MAC)
addresses. In other words, when a router receives a packet from one port,
it looks at the destination network level address (for example, the IP
address) to determine which port to forward the packet to. When a
bridge receives a packet from one port, it looks at the destination MAC
address to determine which port to forward the packet to.
forward packets based on hardware-level, or media access control (MAC)
addresses. In other words, when a router receives a packet from one port,
it looks at the destination network level address (for example, the IP
address) to determine which port to forward the packet to. When a
bridge receives a packet from one port, it looks at the destination MAC
address to determine which port to forward the packet to.
In each case, the unit maintains either a forwarding table (bridges) or a
routing table (routers) that contains information about which port to use
to reach the destination address. These tables are for the most part
maintained automatically by the unit so the administrator does not have
to add or delete entries as the network topology changes.
routing table (routers) that contains information about which port to use
to reach the destination address. These tables are for the most part
maintained automatically by the unit so the administrator does not have
to add or delete entries as the network topology changes.
An example illustrating the difference between bridges and routers would
be the case where both a bridge and a router have tables with 256
entries. Because the bridge forwards based on MAC address, it can know
about the location of 256 MAC addresses (physical machines such as
workstations, servers, etc.). The router can know about the location of
256 networks, where each network can contain many physical machines.
be the case where both a bridge and a router have tables with 256
entries. Because the bridge forwards based on MAC address, it can know
about the location of 256 MAC addresses (physical machines such as
workstations, servers, etc.). The router can know about the location of
256 networks, where each network can contain many physical machines.
Bridges make forwarding decisions based on destination addresses, while
routers makes forwarding decisions based on networks to which
destination addresses belong. Therefore, routers are more efficient and
capable of handling more traffic.
routers makes forwarding decisions based on networks to which
destination addresses belong. Therefore, routers are more efficient and
capable of handling more traffic.
The OfficeConnect Remote 840 provides a Bridge Firewall function which
allows flexible configuration of simultaneous bridging and routing. For
more information on the Bridge Firewall, see Appendix A,
allows flexible configuration of simultaneous bridging and routing. For
more information on the Bridge Firewall, see Appendix A,
.
MAC-Encapsulated
Routing
MAC-Encapsulated Routing enables the OfficeConnect Remote 840 to
function as a router but to work in a bridged environment. When
enabled, the network level addresses are used for forwarding, but the
function as a router but to work in a bridged environment. When
enabled, the network level addresses are used for forwarding, but the
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