DELL N3000 User Manual

412

Monitoring Switch Traffic

For each source port, you can specify whether to mirror ingress traffic (traffic

the port receives, or RX), egress traffic (traffic the port sends, or TX), or both

ingress and egress traffic.

The packet that is copied to the destination port is in the same format as the

original packet on the wire. This means that if the mirror port is copying a

received packet, the copied packet is VLAN tagged or untagged as it was

received on the source port. If the mirror is copying a transmitted packet, the

copied packet is VLAN tagged or untagged as it is being transmitted on the

source port. Destinations include physical interfaces and RSPAN VLANs.
After you configure the port mirroring session, you can enable or disable the

administrative mode of the session to start or stop the probe port from

receiving mirrored traffic.

Port Mirroring Behaviors

The following behaviors are applicable to monitor ports:

• The destination port loses its VLAN configuration when port mirroring is

enabled. The VLAN configuration is restored when the port is no longer

configured for a monitor session. The mirrored source and the transit ports

retain their VLAN configuration. Transit ports must be members of the

RSPAN VLAN.

• When port mirroring is enabled, all MAC address entries associated with

destination ports are purged. This prevents transmitting packets out of the

port that are not seen on the mirrored port. If spanning tree is enabled, this

is treated as a topology change.

• The spanning tree protocol is disabled on destination ports such that

frames are always received from or transmitted out of the port as soon as

the port is up (spanning tree status is forwarding and role is disabled). This

is analogous to always setting the spanning tree state of the port to

forwarding. When a port is no longer configured to be the destination

port, spanning tree is re-enabled for that port, if configured. Note that the

NOTE:

You can create a DiffServ policy class definition or an ACL that mirrors

specific types of traffic to a destination port. For more information, see