Cabletron Systems 9E312, 9E423 An Overview of Remote Bridge Management

9E312/9E423 Module Bridging

In Source Route bridging, the source node sends “explorer” packets to a

destination node that pass through a bridged network. Each bridge that sees the

explorer packet will append Routing Information (in the form of LAN segment

numbers) to it. When the destination node receives these explorer packets, it will

return a response to the source node that contains the route information ﬁeld

indicating which bridge paths the explorer packets took. In future communication

between the two nodes, the original source node will append the best route to the

destination node in a Routing Information Field (RIF) of its data frames, so that a

bridge on the network will simply have to examine the RIF to verify whether it is

a part of the route process.

Transparent bridges are most common in Ethernet networks. Individual

Transparent bridges monitor packet trafﬁc on attached network segments to learn

their network segment location in terms of which bridge port receives packets

originated from a particular station (determined via the packet’s Source Address

ﬁeld). This information gets stored in the bridge’s Filtering Database. When in the

Forwarding state, the bridge compares a packet’s destination address to the

information in the Filtering Database to determine if the packet should be

forwarded to another network segment or ﬁltered (i.e., not forwarded). A bridge

ﬁlters a packet if it determines that the packet’s destination address exists on the

same side of the bridge as the source address.

Transparent bridges in a network communicate with one another by exchanging

Bridge Protocol Data Units, or BPDUs, and collectively implement a Spanning

Tree Algorithm (STA) to determine the network topology, to ensure that only a

single data route exists between any two end stations, and to ensure that the

topology information remains current.

An Overview of Remote Bridge Management

With SPECTRUM Element Manager, you can view and manage bridging across

the 9E312/9E423 Module — and at each bridging interface — by using the

following windows:

• The Bridge Status window provides you with basic information about the

current status of the 9E312/9E423 Module’s bridging interfaces, and allows

you to enable or disable bridging at each interface of the switch. The Bridge

Status window also lets you access further windows to conﬁgure bridging at

the 9E312/9E423 Module.

• The Performance Graph and Interface Statistics windows graphically display

the trafﬁc passing between bridged networks, and let you compare and

contrast trafﬁc processed by each interface.