ServerIron ADX Security Guide 73
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Enabling ACL filtering of fragmented packets 2
On an individual interface basis, you can configure an IronCore device to automatically drop a
fragment whose source and destination IP addresses exactly match an ACL entry that has Layer 4
information, even if that ACL entry’s action is permit. To do so, enter the following command at the
configuration level for an interface.
ServerIronADX(config-if-1/1)# ip access-group frag deny
Syntax: [no] ip access-group frag deny

Clearing the ACL statistics

Statistics on the ACL account report can be cleared:
•When a software reload occurs
•When the ACL is bound to or unbound from an interface
•When you enter the clear access-list command, as in the following example.
ServerIronADX(config)# clear access-list all
Syntax: clear access-list all | ethernet <slot>/<port>
Enter all to clear all statistics for all ACLs.
Use ethernet <slot>/<port> to clear statistics for ACLs a physical port.
Enabling ACL filtering of fragmented packets

Filtering fragmented packets for rule-based ACLs

By default, when a rule-based ACL is applied to a port, the port will use the ACL to permit or deny
the first fragment of a fragmented packet, but forward subsequent fragments of the same packet
in hardware. Generally, denying the first fragment of a packet is sufficient, since a transaction
cannot be completed without the entire packet.
NOTE
The fragmentation support described in this section applies only to rule-based ACLs.
NOTE
Enhanced fragment handling is not supported on 10 Gigabit Ethernet modules. By default, 10
Gigabit Ethernet modules also forward the first fragment instead of using the ACLs to permit or deny
the fragment.
For tighter control, you can enable CPU filtering of all packet fragments on a port. When you enable
CPU filtering, the port sends all the fragments of a fragmented packet to the CPU. The CPU then
permits or denies each fragment according to the ACL applied to the port. You can enable CPU
filtering of fragments on individual ports.
You also can configure the port to drop all packet fragments.
To enable CPU filtering of packet fragments on an individual port, enter commands such as the
following.
ServerIronADX(config)# interface ethernet 1/1
ServerIronADX(config-if-1/1)# ip access-group frag inspect