Cisco Systems BC-109 manual Tune the SRB Network, Alter Access Lists Used in Access Expressions

Tune the SRB Network

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:

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Enable or Disable the Source-RouteFast-Switching Cache

Enable or Disable the Source-RouteAutonomous-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.

Configuring Source-Route Bridging BC-139