Port Monitor Commands - Dell N1100-ON Reference Manual

Port Monitor Commands

Dell EMC Networking N1100-ON/N1500/N2000/N2100-
ON/N3000/N3100-ON/N4000 Series Switches
Dell EMC Networking switches allow the user to monitor traffic with an
external network analyzer. The external network analyzer can use any of the
Ethernet ports as a probe port. The probe port transmits a mirror copy of the
traffic being probed. Network traffic transmission is always disrupted
whenever a configuration change is made for port monitoring. Therefore,
whenever port monitoring is enabled, the probe port does not always forward
traffic as a normal port. When diagnosing problems, an operator should
always check the status of port monitoring.
The port monitoring feature allows the user to configure a session. A session
consists of one destination or probe port and one or multiple source ports.
When a session is enabled, any traffic entering or leaving the source ports of
that session is copied (mirrored) onto the corresponding destination port. A
network traffic analyzer can be attached to destination ports to analyze the
traffic patterns of source ports.
A session is operationally active only if both a destination port and at least
one source port are configured. If neither is true, the session is inactive. A port
configured as a destination port acts as a mirroring port when the session is
operationally active. If it is not, the port acts as a normal port and participates
in all normal operation with respect to transmitting traffic.
The port mirroring logic stage occurs after the after the VLAN tag processing
stage on ingress and before the VLAN tag processing stage on egress. When
mirroring packets associated with DVLAN/QinQ SP or CE ports, the outer
VLAN tag may or may not appear in the frame. Due to the internal processing
of QinQ tagging, the TPID of ingress frames mirrored from the SP port will
always be 0x8100. In addition, packets forwarded internally across a stacking
link may have different tags applied than packets forwarded on a local egress
port. This is due to the processing required for forwarding across a stack.
Any Ethernet port may be configured as a source port.
Caveats:
• Platforms may behave unpredictably if an attempt is made to mirror a port
of greater speed than the probe port.
Layer 2 Switching Commands
637