Users Guide

If ACL logging is stopped because the congured threshold is exceeded, it is re-enabled after the logging interval
period elapses. ACL logging is supported for standard and extended IPv4 ACLs, IPv6 ACLs, and MAC ACLs. You
can congure ACL logging only on ACLs that are applied to ingress interfaces; you cannot enable logging for ACLs
that are associated with egress interfaces.
You can activate ow-based monitoring for a monitoring session by entering the flow-based enable
command in the Monitor Session mode. When you enable this capability, trac with particular ows that are
traversing through the ingress and egress interfaces are examined and, appropriate ACLs can be applied in both
the ingress and egress direction. Flow-based monitoring conserves bandwidth by monitoring only specied trac
instead all trac on the interface. This feature is particularly useful when looking for malicious trac. It is available
for Layer 2 and Layer 3 ingress and egress trac. You may specify trac using standard or extended access-lists.
This mechanism copies all incoming or outgoing packets on one port and forwards (mirrors) them to another port.
The source port is the monitored port (MD) and the destination port is the monitoring port (MG).
Related Commands
• permit – assign a permit lter for IP packets.
permit icmp (for IPv6 ACLs)
To allow all or specic internet control message protocol (ICMP) messages, congure a lter.
Syntax
permit icmp {source address mask | any | host ipv6-address} {destination
address | any | host ipv6-address} [message-type] [ttl operator] [count [byte]]
[log [interval minutes] [threshold-in-msgs [count]] [monitor]
To remove this lter, you have two choices:
• Use the no seq sequence-number command if you know the lter’s sequence number.
•
Use the no permit icmp {source address mask | any | host ipv6-address}
{destination address | any | host ipv6-address} command.
Parameters
source address
mask
Enter a network mask in /prex format (/x) or A.B.C.D. The mask, when specied in
A.B.C.D format, may be either contiguous or non-contiguous.
any Enter the keyword any to specify that all routes are subject to the lter.
host ip-v6address Enter the keyword host then the IPv6 address to specify a host IP address.
destination Enter the IP address of the network or host to which the packets are sent.
ttl Enter the keyword ttl to permit a packet based on the time to live value. The range is
from 1 to 255.
operator Enter one of the following logical operand:
• eq(equal to) — matches packets that contain a ttl value that is equal to the specied
ttl value.
• neq(not equal to) — matches packets that contain a ttl value that is not equal to the
specied ttl value.
•
gt(greater than) — matches packets that contain a ttl value that is greater than the
specied ttl value.
• lt (less than) — matches packets that contain a ttl value that is less than the
specied ttl value.
• range(inclusive range of values) — matches packets that contain a ttl value that
falls between the specied range of ttl values.
Access Control Lists (ACL) 351