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Chapter 34 Configuring Network Security with ACLs
Configuring IPv4 ACLs
Use one of these workarounds:
•
Modify the ACL configuration to use fewer resources.
•
Rename the ACL with a name or number that alphanumerically precedes the ACL names or
numbers.
To determine the specialized hardware resources, enter the
show platform layer4 acl map
privileged
EXEC command. If the switch does not have available resources, the output shows that index 0 to
index 15 are not available.
For more information about configuring ACLs with insufficient resources, see CSCsq63926 in the Bug
Toolkit.
For example, if you apply this ACL to an interface:
permit tcp
source source-wildcard
destination destination-wildcard
range 5 60
permit tcp
source source-wildcard
destination destination-wildcard
range 15 160
permit tcp
source source-wildcard
destination destination-wildcard
range 115 1660
permit tcp
source source-wildcard
destination destination-wildcard
And if this message appears:
ACLMGR-2-NOVMR: Cannot generate hardware representation of access list [chars]
The flag-related operators are not available. To avoid this issue,
•
Move the fourth ACE before the first ACE by using
ip access-list resequence
global configuration
command:
permit tcp
source source-wildcard
destination destination-wildcard
permit tcp
source source-wildcard
destination destination-wildcard
range 5 60
permit tcp
source source-wildcard
destination destination-wildcard
range 15 160
permit tcp
source source-wildcard
destination destination-wildcard
range 115 1660
or
•
Rename the ACL with a name or number that alphanumerically precedes the other ACLs (for
example, rename ACL
79
to ACL
1
).
You can now apply the first ACE in the ACL to the interface. The switch allocates the ACE to available
mapping bits in the Opselect index and then allocates flag-related operators to use the same bits in the
hardware memory.
IPv4 ACL Configuration Examples
This section provides examples of configuring and applying IPv4 ACLs. For detailed information about
compiling ACLs, see the
Cisco IOS Security Configuration Guide, Release 12.2
and to the Configuring
IP Services” section in the “IP Addressing and Services” chapter of the
Cisco IOS IP Configuration
Guide, Release 12.2.
shows a small networked office environment with routed Port 2 connected to blade server A,
containing benefits and other information that all employees can access, and routed Port 1 connected to
blade server B, containing confidential payroll data. All users can access blade server A, but Blade
server B has restricted access.
Use router ACLs to do this in one of two ways:
•
Create a standard ACL, and filter traffic coming to the server from port 1.
•
Create an extended ACL, and filter traffic coming from the server into port 1.