Filter
Top Products
22
CrossFire 8600/8605 Token-Ring Switches v. 1.2, P/N: 710001641 Switch Theory of Operation
Source-routed frames are switched across logical rings by Source-Route Bridging
and within each logical ring by Source-Route Switching.
The Bridge Relay Function runs the IEEE 802.1D Spanning Tree Protocol.
Duplicate MAC addresses are
not
allowed.
SRT/SRB
This is a special mode combining SRT and the SRB switching modes. Each Logical
Ring will operate either in SRT mode or in SRB mode. Transparent bridging will
only take place between logical rings in SRT mode. Source-route bridging will take
place between all logical rings.
The purpose of the SRT/SRB mode is to allow duplicate MAC addresses to be used
when in SRT mode. The ports on which the duplicate MAC addresses reside can be
reached only by source routing.
The Bridge Relay Function runs the IBM Spanning Tree Protocol on the SRB
logical rings to eliminate parallel paths with all source route bridges. It runs IEEE
802.1D Spanning Tree Protocol on the SRT logical rings to eliminate parallel paths
with other SRT bridges. The two resulting spanning trees are joined together.
The IEEE 802.1D Spanning Tree Protocol is still used to eliminate parallel paths
within each logical ring whether it is SRB or SRT.
The benefit of the SRT/SRB mode is that it allows part of the network to be run in
SRT mode to accommodate applications that do not support source routing, while
still supporting duplicate MAC addresses on a number of SRB ports (for example,
for SNA gateway applications).
Filtering
Filtering is important for a LAN switch. Filters can be used to reduce broadcast
traffic, block certain protocols and provide security functions.
The switch provides filters for:
•
Destination or source MAC addresses
•
Destination service access point (DSAP)
•
Subnetwork Access Protocol (SNAP) type
Each protocol filter can be applied on a per-port basis for both input and output
traffic. This feature allows certain protocols to be blocked from certain ports. For
example, filters can be established to allow only Systems Network Architecture
(SNA) traffic to flow to ports with SNA gateways.
Source and destination MAC address filtering can be applied to all incoming
frames. The MAC address filters act in one of three ways: