Allied Telesis x900-24 series Profile mask, Following figure shows the copies of these rules

How many filters can you create?

The following figure shows the copies of these rules.

Port	Start
1	1
2	1
3	1
4	9
5	9
6	1
...	...
...	...
52	1

Table that maps ingress port to the starting point of the rule comparison process

1		Rule 1
2		Rule 2
3		Rule 3
4		Rule 4
5
6
7
8
9		Copy of rule 1
10		Copy of rule 2
11		Copy of rule 3
12		Copy of rule 4
13		QoS rule #1
14		QoS rule #2
	Rule table

When a QoS policy has been applied to ports 4 and 5, all the hardware filter rules have to be replicated further down in the rule table, and the QoS-specific rules added to the table below this copy of the hardware filter rules. For ports 4 and 5, the rule comparison process starts at entry 9 in the rule table, not at entry 1.

The entries 5-8 in the table have been left blank because separate sets of rules in the rule table must begin at an 8-entry boundary.

So, if there are several QoS policies configured on the switch, then there will be several copies of the hardware filter rules within the rule table. This, of course, can significantly reduce the maximum number of hardware filters that can be created.

Also, the protocols that use filters (see page 11) create at least one entry each.

2. The profile (mask)

The other item that affects the number of filters you can create is called the profile. Conceptually, this is a 16-byte mask that decides which set of bytes should be extracted from a packet as it enters the filtering process, to be compared against all the hardware filter and QoS classifiers. Hardware filters and QoS share a single mask.

In effect, the mask is the sum of all the individual bytes required for each individual classifier parameter. The number of bytes required by each classifier parameter depends on what fields it maps on. For example:

source MAC address—6 bytes

destination MAC address—6 bytes

Page 9 AlliedWare™ OS How To Note: Hardware Filters