Cisco Systems BC-109 manual Configure NetBIOS Access Filters Using a Byte Offset

Secure the SRB Network

The NetBIOS station access list contains the station name to match, along with a permit or deny condition. You must assign the name of the access list to a station or set of stations on the network.

To assign a station access list name, use the following command in global configuration mode:

Command	Purpose
netbios access-list host name {permit deny} pattern	Assign the name of an access list to a
	station or set of stations on the network.

When filtering by station name, you can choose to filter either incoming or outgoing messages on the interface. To specify the direction, use one of the following commands in interface configuration mode:

Command	Purpose
netbios input-access-filter host name	Define an access list filter for incoming
	messages.
netbios output-access-filter host name	Define an access list filter for outgoing
	messages.

Configure NetBIOS Access Filters Using a Byte Offset

To configure access filters you must do the following:

Step 1 Assign a byte offset access list name.

Step 2 Specify the direction of the message to be filtered on the interface.

Keep the following notes in mind while configuring access filters using a byte offset:

•When an access list entry has an offset plus the length of the pattern that is larger than the packet’s length, the entry will not make a match for that packet.

•Because these access lists allow arbitrary byte offsets into packets, these access filters can have a significant impact on the amount of packets per second transiting across the bridge. They should be used only when situations absolutely dictate their use.

The NetBIOS byte offset access list contains a series of offsets and hexadecimal patterns with which to match byte offsets in NetBIOS packets. To assign a byte offset access list name, use the following command in global configuration mode:

Command	Purpose
netbios access-list bytes name {permit deny} offset	Define the byte offsets and patterns
pattern	within NetBIOS messages to match
	with access list parameters.

Note Using NetBIOS Byte Offset access filters disables the autonomous or fast switching of source-route bridging frames.

When filtering by byte offset, you can filter either incoming or outgoing messages on the interface. To specify the direction, use one of the following commands in interface configuration mode:

	Command	Purpose
	netbios input-access-filter bytes name	Specify a byte-based access filter on
		incoming messages.
BC-134Bridging and IBM Networking Configuration Guide