Restrictions To Baystack 281Xx Switches In Bridged And Routed Networks; Filtering Lattisspan Packets In Bridged Networks - Bay Networks BayStack 281 Series Manual

Restrictions to BayStack 281xx Switches in Bridged and Routed
Networks

Filtering LattisSpan Packets in Bridged Networks

893-00965-A

Restrictions to BayStack 281xx Switches in Bridged and Routed Networks

Bridges and routers provide some restrictions for deploying BayStack 281xx
switches and creating virtual LANs. Two core concepts about routers and
switches must be understood.
• Virtual LANs created by BayStack 281xx switches are equivalent to a
broadcast domain. Broadcast and multicast frames are always forwarded
to other devices within a given virtual LAN.
• Routers segment the broadcast domain. Routers do not forward broadcast
or multicast frames though their interfaces (unless they are configured to
support bridging protocols).
This section discusses the effect of LattisSpan topology management packets
within bridged and routed network environments.
Special consideration must also be given to using BayStack 281xx switches in
networks that include routers with bridging software enabled, MAC-level
bridges, and repeaters.
NOTE: When you use any of these devices to connect two or more
BayStack 281xx switches, LattisSpan multicast packets must be filtered and
discarded by the internetworking device. LattisSpan multicast packets should
be prevented from passing through the internetworking device. However,
LattisSpan multicast packets can pass through devices, such as a fiber optic
repeater and a remote bridge, that are used to extend the distance of a
LattisSpan trunk link.
The BayStack 281xx switch uses special multicast packets to execute the
topology management process. All BayStack 281xx switches within a
community exchange topology information using these LattisSpan multicast
packets to establish trunk ports, break loops, and construct topology databases.
As router or bridge connections to the BayStack 281xx switch are established
(using the RJ-45 ports), the new source addresses are learned and added to the
port MAC Store Table after the new devices send data to the switch.
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