Configuring Transparent Bridging
Transparent and SRT Bridging Configuration Examples
BC-79
Cisco IOS Bridging and IBM Networking Configuration Guide
Figure 21 Bridged Subnetworks with Domains
For proper bridging operation, the bridged subnetworks cannot have connections between them, but they
can be connected to the same backbone. In this example, three of the four bridged subnetworks are
connected to the FDDI backbone and each belongs to a separate domain.
Domains used in this topology allow the bridged subnetworks to be independent of one another while
still bridging traffic onto the backbone destined for other connected bridged subnetworks. Domains can
be used in this manner only if the bridged subnetworks have a single point of attachment to one another.
In this case, the connection to the FDDI backbone is that single point of attachment.
Each router on which a domain is configured and that has a single point of attachment to the other
bridged subnetworks, checks whether a BPDU on the backbone is its own. If the BPDU does not belong
to the bridged subnetwork, the Cisco IOS software ignores the BPDU.
Separate bridged subnetworks, as in this example, allow spanning-tree reconfiguration of individual
bridged subnetworks without disrupting bridging among the other bridged subnetworks.
Router A Router B
Router D
Domain 1 Domain 2
Domain 3
33 33
3
E0 E2 E3
F0
F0 1
1
555
55
E4
S0 S1 S2
Bridged Subnetwork
Bridged Subnetwork
1
11
T1 T2
Router C
Circuit group 7
Circuit group 4
E1
E2
FDDI
To other
parts of BSN
E1
To other
parts of BSN
To other
parts of BSN
222
F0
2
S2322
E5
To other
parts of BSN
Bridged Subnetwork
S2 S0 S1
Bridged Subnetwork