Configuring Transparent Bridging
Transparent and SRT Bridging Configuration Task List
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Cisco IOS Bridging and IBM Networking Configuration Guide
To reduce the amount of bandwidth that LAT traffic consumes on serial interfaces, you can specify a
LAT-specific form of compression. Doing so applies compression to LAT frames being sent out by the
Cisco IOS software through the interface in question. To configure LAT compression, use the following
command in interface configuration mode:
LAT compression can be specified only for serial interfaces. For the most common LAT operations (user
keystrokes and acknowledgment packets), LAT compression reduces LAT’s bandwidth requirements by
nearly a factor of two.
Establishing Multiple Spanning-Tree Domains
The Cisco IEEE 802.1D bridging software supports spanning-tree domains of bridge groups. Domains
are a feature specific to Cisco. This feature is only available if you have specified IEEE as the
Spanning-Tree Protocol. A domain establishes an external identification of the BPDUs sent from a
bridge group. The purpose of this identification is as follows:
•Bridge groups defined within the domain can recognize that BPDU as belonging to them.
•Two bridged subnetworks in different domains that are sharing a common connection can use the
domain identifier to identify and then ignore the BPDUs that belong to another domain. Each
bridged subnetwork establishes its own spanning tree based on the BPDUs that it receives. The
BPDUs it receives must contain the domain number to which the bridged subnetwork belongs.
Bridged traffic is not domain identified.
Note Domains do not constrain the propagation of bridged traffic. A bridge bridges nonrouted
traffic received on its interfaces regardless of domain.
You can place any number of routers or bridges within the domain. Only the devices within a domain
share spanning-tree information.
When multiple routers share the same cable and you want to use only certain discrete subsets of those
routers to share spanning-tree information with each other, establish spanning-tree domains. This
function is most useful when running other applications, such as IP User Datagram Protocol (UDP)
flooding, that use the IEEE spanning tree. You also can use this feature to reduce the number of global
reconfigurations in large bridged networks.
To establish multiple spanning-tree domains, use the following command in global configuration mode:
For an example of how to configure domains, see the “Complex Transparent Bridging Network Topology
Example” section later in this chapter.
Command Purpose
bridge-group bridge-group lat-compression Reduces the amount of bandwidth that LAT traffic consumes on a
serial interface.
Command Purpose
bridge bridge-group domain domain-number Establishes a multiple spanning-tree domain.