Cisco Systems BC-109 manual Configure Administrative Filters for Token Ring Traffic

Configure Administrative Filters for Token Ring Traffic

Command	Purpose
netbios output-access-filter bytes name	Specify a byte-based access filter on
	outgoing messages.

Configure Administrative Filters for Token Ring Traffic

Source-route bridges normally filter frames according to the routing information contained in the frame. That is, a bridge will not forward a frame back to its originating network segment or any other network segment that the frame has already traversed. This section describes how to configure another type of filter—the administrative filter.

Administrative filters can filter frames based on the following methods:

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Protocol type—IEEE 802 or Subnetwork Access Protocol (SNAP)

Token Ring vendor code

Source address

Destination address

Whereas filtering by Token Ring address or vendor code causes no significant performance penalty, filtering by protocol type significantly affects performance. A list of SNAP (Ethernet) type codes is provided in the “Ethernet Type Codes” appendix in the Bridging and IBM Networking Command Reference.

Filter Frames by Protocol Type

You can configure administrative filters by protocol type by specifying protocol type codes in an access list. You then apply that access list to either IEEE 802.2 encapsulated packets or to SNAP-encapsulated packets on the appropriate interface.

The order in which you specify these elements affects the order in which the access conditions are checked. Each condition is tested in succession. A matching condition is then used to execute a permit or deny decision. If no conditions match, a deny decision is reached.

Note If a single condition is to be denied, there must be an access-listcommand that permits everything as well, or all access is denied.

To filter frames by protocol type, use the following command in global configuration mode:

Command	Purpose
access-listaccess-list-number {permit deny} {type-code	Create an access list for filtering
wild-mask address mask}	frames by protocol type.

You can filter IEEE 802-encapsulated packets on either input or output. The access list you specify is the one you created that includes the protocol type codes.

Configuring Source-Route Bridging BC-135