Corebuilder 2500 Bridging And Routing - 3Com CoreBuilder 2500 User Manual

3-6 C 3: B
HAPTER RIDGING AND
CoreBuilder 2500
Bridging and Routing
R C
OUTING IN THE ORE
The destination MAC address determines whether the CoreBuilder 2500
system bridges or routes a packet. Before a host system sends a packet to
another host, the host system compares its own network address to the
network address of the other host as follows:
If network addresses are on the same subnetwork, the packet is
bridged directly to the destination host's address.
If network addresses are on different subnetworks, the packet must
be routed from one to the other. In this case, the host transmits the
packet to the connecting router's MAC address.
Figure 3-6 illustrates CoreBuilder 2500 bridging:
1 The packet enters the CoreBuilder 2500 system.
2 The bridging layer examines the packet's destination MAC address. The
destination MAC address does not correspond to the MAC address of
one of the system ports configured for routing.
3 The bridging layer selects a segment (port) based on the destination MAC
address and forwards the packet to that segment.
2
1
Transmitting host
Destination host
Figure 3-6 CoreBuilder 2500 Bridging
B 2500 S
UILDER YSTEM
Router
1 2
3
Bridge
1 2
Routing layer
3
Router interfaces
Bridging layer
3 Subnetworks