Determining Layer 4 Operation Usage; Determining Logical Operation Unit Usage - Cisco 7604 Configuration Manual
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Guidelines and Restrictions for Using Layer 4 Operators in ACLs
Determining Layer 4 Operation Usage
You can specify these types of operations:
•
•
•
•
•
We recommend that you do not specify more than nine different operations on the same ACL. If you
exceed this number, each new operation might cause the affected ACE to be translated into more than
one ACE.
Use the following two guidelines to determine Layer 4 operation usage:
•
•
Determining Logical Operation Unit Usage
Logical operation units (LOUs) are registers that store operator-operand couples. All ACLs use LOUs.
There can be up to 32 LOUs; each LOU can store two different operator-operand couples with the
exception of the range operator. LOU usage per Layer 4 operation is as follows:
•
•
•
•
•
For example, this ACL would use a single LOU to store two different operator-operand couples:
... Src gt 10 ...
... Dst gt 10
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
34-8
gt (greater than)
lt (less than)
neq (not equal)
eq (equal)
range (inclusive range)
Layer 4 operations are considered different if the operator or the operand differ. For example, in this
ACL there are three different Layer 4 operations ("gt 10" and "gt 11" are considered two different
Layer 4 operations):
... gt 10 permit
... lt 9 deny
... gt 11 deny
There is no limit to the use of "eq" operators as the "eq" operator does not use a logical
Note
operator unit (LOU) or a Layer 4 operation bit. See the
Unit Usage" section on page 34-8
Layer 4 operations are considered different if the same operator/operand couple applies once to a
source port and once to a destination port. For example, in this ACL there are two different Layer 4
operations because one ACE applies to the source port and one applies to the destination port.
... Src gt 10 ...
... Dst gt 10
gt uses 1/2 LOU
lt uses 1/2 LOU
neq uses 1/2 LOU
range uses 1 LOU
eq does not require a LOU
Chapter 34
Understanding Cisco IOS ACL Support
"Determining Logical Operation
for a description of LOUs.
OL-4266-08
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