Allied Telesis x900-48 series Functiehandboek - Pagina 15
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Pagina afdrukkenExample 2: ports 5004-5008
In some more complex situations, we may need more than one classifier to cover all the
range we want to. Let's take UDP destination ports between 5004-5008
5004
5005
5006
5007
5008
According to the bolded bits, we may think that the changed bits are the last 5 bits so the
mask should be 11111111 11100000.
But remember that if we set the last 5 bits to 0, the mask will cover 2
want to cover only 5 ports, so let's divide 5 into 4+1.
5004
5005
5006
5007
5008
Now it is really easy to write the classifiers!
Example 3: ports 333-777
A more complex situation, let's try to write the classifiers for UDP ports between 333-777.
As we are trying to get rid of odd numbers in the beginning of our port range, we will prefer
to write classifiers for single port number for 333.
777-334+1 = 444 total number of port (+1 for including 333)
256 + 128 + 32 + 16 + 8 + 4 = 444 (7 classifiers)
7 classifiers + 1 classifier (for 333) = 8 classifiers
Now the question is how to locate these blocks. The short-cut to do that is, first, find the
position of the biggest block, which is 256 for our example. 256 should fit into one of the
following blocks:
0
256
512
768
...
65280
Page 15 | AlliedWare™ OS How To Note: Hardware Filters
=
00010011 10001100
=
00010011 10001101
=
00010011 10001110
=
00010011 10001111
=
00010011 10010000
=
00010011 10001100
=
00010011 10001101
=
00010011 10001110
=
00010011 10001111
=
00010011 10010000
create class=1 udpdp=5004 l4dmask=FFFC
create class=2 udpdp=5008
add swi hwfilt class=1,2 action=drop
-
255
-
512
-
767
-
1024
-
65536
Appendix A: How to use the layer 4 mask in classifiers
4 ports
+
1 port
5
= 32 ports. But we