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Tune the SRB Network
Configuring Source-Route Bridging BC-139
The access lists defined in the previous section create the following configuration:
interface tokenring 0
access-expression in ~lsap(202) | dmac(701)
!
access-list 202 permit 0x0404 0x0001 ! Permits SNA frames (command or response)
access-list 202 permit 0x0004 0x0001 ! Permits SNA Explorers with NULL DSAP
!
! Access list 701 will permit the FEP MAC address
! of 0110.2222.3333
access-list 701 permit 0110.2222.3333
This is a better and simpler access list than the one originally introduced and will probably result in
better run-time execution as a result. Therefore, it is best to simplify your access expressions as much
as possible before configuring them into the Cisco IOS software.
Note An “access-expression” type filter cannot exist with a “source-bridge” type filter on the same
interface. The two types of filters are mutually exclusive.
Alter Access Lists Used in Access Expressions
Because access expressions are composed of access lists, special care must be taken when deleting
and adding access lists that are referenced in these access expressions.
If an access list that is referenced in an access expression is deleted, the access expression merely
ignores the deleted access list. However, if you want to redefine an access list, you can create a new
access list with the appropriate definition and use the same name as the old access list. The newly
defined access list replaces the old one of the same name.
For example, if you want to redefine the NetBIOS access list named MIS that was used in the
preceding example, you would use the following sequence of configuration commands:
! Replace the NetBIOS access list
interface tokenring 0
access-expression in (smac(701) & netbios-host(accept))
no netbios access-list host accept permit CISCO*
Tune the SRB Network
The following sections describe how to configure features that enhance network performance by
reducing the number of packets that traverse the backbone network:
• Enable or Disable the Source-Route Fast-Switching Cache
• Enable or Disable the Source-Route Autonomous-Switching Cache
• Enable or Disable the SSE
• Establish the Connection Timeout Interval
• Optimize Explorer Processing
• Configure Proxy Explorers
Note In some situations, you might discover that default settings for LLC2 configurations are not
acceptable. In such a case, you can configure LLC2 for optimal use. The chapter “Configuring LLC2
and SDLC Parameters” in this publication describes how you can use them to optimize your network
performance.