Users Guide

Behavior of Flow-Based Monitoring
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 interfaces are examined, and
appropriate ACLs can be applied in the ingress direction. By default, ow-based monitoring is not enabled.
You must specify the monitor option with the permit, deny, or seq command for ACLs that are assigned to the source or the
monitored port (MD) to enable the evaluation and replication of trac that is traversing to the destination port. Enter the keyword
monitor with the seq, permit, or deny command for the ACL rules to allow or drop IPv4, IPv6, ARP, UDP, EtherType, ICMP, and TCP
packets. The ACL rule describes the trac that you want to monitor, and the ACL in which you are creating the rule will be applied to the
monitored interface. Flow monitoring is supported for standard and extended IPv4 ACLs, standard and extended IPv6 ACLs, and standard
and extended MAC ACLs.
CONFIG-STD-NACL mode
seq sequence-number {deny | permit} {source [mask] | any | host ip-address} [count [byte]]
[order] [fragments] [log [threshold-in-msgs count]] [monitor]
If the number of monitoring sessions increases, inter-process communication (IPC) bandwidth utilization will be high. The ACL manager
might require a large bandwidth when you assign an ACL, with many entries, to an interface.
The ACL agent module saves monitoring details in its local database and also in the CAM region to monitor packets that match the
specied criterion. The ACL agent maintains data on the source port, the destination port, and the endpoint to which the packet must be
forwarded when a match occurs with the ACL entry.
If you congure the flow-based enable command and do not apply an ACL on the source port or the monitored port, both ow-based
monitoring and port mirroring do not function. Flow-based monitoring is supported only for ingress trac and not for egress packets.
The port mirroring application maintains a database that contains all monitoring sessions (including port monitor sessions). It has
information regarding the sessions that are enabled for ow-based monitoring and those sessions that are not enabled for ow-based
monitoring. It downloads monitoring conguration to the ACL agent whenever the ACL agent is registered with the port mirroring
application or when ow-based monitoring is enabled.
The show monitor session session-id command has been enhanced to display the Type eld in the output, which indicates
whether a particular session is enabled for ow-monitoring.
Example Output of the show Command
Dell(conf-mon-sess-0)#do show monitor session 0
SessID Source Destination Dir Mode Source IP Dest IP
------ ------ ----------- --- ---- --------- --------
0 Te 1/1/1/1 Te 1/1/1/2 rx Flow N/A N/A
The show config command has been modied to display monitoring conguration in a particular session.
Example Output of the show Command
(conf-mon-sess-11)#show config
!
monitor session 11
flow-based enable
source TenGigabitEthernet 1/1/1/1 destination TenGigabitEthernet 1/1/1 direction both
The show ip | mac | ipv6 accounting commands have been enhanced to display whether monitoring is enabled for trac that
matches with the rules of the specic ACL.
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Access Control Lists (ACLs)