CLI Guide

Usage Information
When the congured maximum threshold is exceeded, generation of logs is stopped. When the interval at which
ACL logs are congured to be recorded expires, the subsequent, fresh interval timer is started and the packet
count for that new interval commences from zero. If ACL logging was stopped previously because the congured
threshold is exceeded, it is re-enabled for this new interval.
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
deny tcp — assigns a lter to deny TCP packets.
deny udp — assigns a lter to deny UDP packets.
ip access-list extended — creates an extended ACL.
deny icmp
To drop all or specic internet control message protocol (ICMP) messages, congure a lter.
Syntax
deny icmp {source mask | any | host ip-address} {destination mask | any | host
ip-address} [dscp] [count [byte]] [order] [fragments][threshold-in-msgs]
[count]]
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 deny icmp {source mask | any | host ip-address} {destination mask |
any | host ip-address} command.
Parameters
source Enter the IP address of the network or host from which the packets were sent.
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-address Enter the keyword host then the IP address to specify a host IP address.
destination Enter the IP address of the network or host to which the packets are sent.
dscp Enter this keyword dscp to deny a packet based on the DSCP value. The range is from 0
to 63.
count (OPTIONAL) Enter the keyword count to count packets processed by the lter.
byte (OPTIONAL) Enter the keyword byte to count bytes processed by the lter.
Access Control Lists (ACL) 161