Behavior Of Flow-Based Monitoring - Dell S4820T Configuration Manual

Behavior of Flow-Based Monitoring

Activate flow-based monitoring for a monitoring session by entering the flow-based enable
command in the Monitor Session mode. When you enable this capability, traffic with particular flows that
are traversing through the ingress interfaces are examined, and appropriate ACLs can be applied in the
ingress direction. By default, flow-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 traffic 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 traffic 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 specified 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 configure the flow-based enable command and do not apply an ACL on the source port or the
monitored port, both flow-based monitoring and port mirroring do not function. Flow-based monitoring
is supported only for ingress traffic 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 flow-based monitoring
and those sessions that are not enabled for flow-based monitoring. It downloads monitoring
configuration to the ACL agent whenever the ACL agent is registered with the port mirroring application
or when flow-based monitoring is enabled.
The show monitor session session-id command has been enhanced to display the Type field in
the output, which indicates whether a particular session is enabled for flow-monitoring.
Example Output of the show Command
Dell(conf-mon-sess-0)#do show monitor session 0
SessID Source
------ ------
0 Te 1/1
A
Access Control Lists (ACLs)
Destination
-----------
Te 1/2
Dir Mode Source IP
--- ---- ---------
rx Flow N/A
Dest IP
--------
N/
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