Reference Guide

74 | Access Control Lists (ACLs)
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To configure a filter for an extended IP ACL without a specified sequence number, use any or all of the
following commands in the IP ACCESS LIST mode:
When you use the
log keyword, CP processor logs details about the packets that match. Depending on how
many packets match the log entry and at what rate, the CP may become busy as it has to log these packets’
details.
Figure 6-7 illustrates an extended IP ACL in which the sequence numbers were assigned by the software.
The filters were assigned sequence numbers based on the order in which they were configured (for
example, the first filter was given the lowest sequence number). The
show config command in the IP
ACCESS LIST mode displays the two filters with the sequence numbers 5 and 10.
Figure 6-7. Extended IP ACL
To view all configured IP ACLs and the number of packets processed through the ACL, use the show ip
accounting access-list
command (Figure 232) in the EXEC Privilege mode.
Configuring Layer 2 and Layer 3 ACLs on an Interface
Both Layer 2 and Layer 3 ACLs may be configured on an interface in Layer 2 mode. If both L2 and L3
ACLs are applied to an interface, the following rules apply:
• The packets routed by FTOS are governed by the L3 ACL only, since they are not filtered against an
L2 ACL.
• The packets switched by FTOS are first filtered by the L3 ACL, then by the L2 ACL.
Command Syntax Command Mode Purpose
{deny | permit} {source mask | any |
host ip-address} [count [byte] [dscp]
[
order] [fragments]
CONFIG-EXT-NACL Configure a deny or permit filter to
examine IP packets.
{deny | permit} tcp {source mask] |
any | host ip-address}} [count [byte]
[dscp] [
order] [fragments]
CONFIG-EXT-NACL Configure a deny or permit filter to
examine TCP packets.
{deny | permit} udp {source mask |
any | host ip-address}} [count [byte]
[dscp] [
order] [fragments]
CONFIG-EXT-NACL Configure a deny or permit filter to
examine UDP packets.
FTOS(config-ext-nacl)#deny tcp host 123.55.34.0 any
FTOS(config-ext-nacl)#permit udp 154.44.123.34 0.0.255.255 host 34.6.0.0
FTOS(config-ext-nacl)#show config
!
ip access-list extended nimule
seq 5 deny tcp host 123.55.34.0 any
seq 10 permit udp 154.44.0.0 0.0.255.255 host 34.6.0.0
FTOS(config-ext-nacl)#