Cisco Systems BC-109 Manual De Usuario

 Configuring Source-Route Bridging BC-135

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:

•

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. 

 If a single condition is to be denied, there must be an access-list command that permits 

everything as well, or all access is denied.

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

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. 

netbios output-access-filter bytes name

Specify a byte-based access filter on 
outgoing messages.

{permit | deny}

{type-code 

wild-mask | address mask} 

Create an access list for filtering 
frames by protocol type.