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Alteon OS Application Guide
Appendix A: Troubleshooting
24742C4911, January 2007
NOTE – Traffic on VLAN 4095 is not mirrored to the external ports.
Port Mirroring behavior
This section describes the composition of monitored packets in the GbE Switch Module, based
on the configuration of the ports.
If a tagged port's PVID is the same as its VLAN ID, then the egress traffic on that port is
untagged. Therefore, the following port-mirroring cases are differentiated, as described below:
Tagged or untagged frames from mirrored ports whose VLAN ID is the same as the moni-
toring port's PVID: mirrored frames viewed at the monitoring port are untagged
Tagged or untagged frames from mirrored ports whose VLAN ID is different than the
monitoring port's PVID: mirrored frames viewed at the monitoring port are tagged with
the VLAN ID of ingress/egress port for ingress/egress mirroring respectively.
Layer 2 Port Mirroring
In this scenario, you observe Layer 2 port mirroring.
Same VLAN as Mirrored Port
Both ports tagged: Tagged packet with VID of the VLAN to which the ports belong
Mirrored port tagged, Monitoring port untagged: Untagged packet
Mirrored port untagged, Monitoring port tagged: Tagged packet with VID of the
VLAN to which both ports belong
Both ports untagged: Untagged packet
Different VLAN from Mirrored Port
Both ports tagged: Tagged packet with VID of mirrored port
Mirrored port tagged, Monitoring port untagged: Tagged packet with VID of mirrored
port
Mirrored port untagged, Monitoring port tagged: Tagged packet with VID of mirrored
port
Both ports untagged: Tagged packet with VID of mirrored port