Wildcard Filters - HP 10:10 LAN Bridge MB Installation And Reference Manual

Wildcard Filters

The wildcard filter is a 32-bit binary pattern that can be applied to any 32-bit section at any
location in received packets. The location is determined by specifying a byte offset (the
distance in bytes from the beginning of the packet to the start of the section where the wildcard
filter is to be applied). The bridge compares the wildcard filter to the data in the specified
section in the packet and discards the packet if the bit patterns match. (Use Xs in the wildcard
filter to match either 1 or 0 in the corresponding bit position in the packet.)
Example wildcard filter
Start of frame
compare bits and discard
the packet if they match
Byte offset
Example IEEE 802.3 or Ethernet packet
Figure 6-1. How the Wildcard Filter Works
You can specify up to two wildcard filters. They may consist of different bit patterns and byte
offsets. The bridge applies each filter to the received packet independently. See chapter 3,
"Configuration", for the wildcard filter configuration process and some examples.
These filters can be applied to any section of an IEEE 802.3 or Ethernet packet: source or
destination addresses, packet length (for 802.3 packets), packet type (for Ethernet packets), data
field, and even the CRC. Because it is possible to specify patterns within the MAC data field,
wildcard filters can also be used for protocol filtering.
Note that, because of the extra processing required, the use of wildcard filters may reduce
bridge performance slightly.
How the Bridge Works 6-5