on a Cisco Switch
Access ports only
sends untagged frames and belongs to and carries the traffic of only one VLAN.
Traffic is received and sent in native formats with no VLAN tagging. Anything
arriving on an access port is assumed to belong to the VLAN assigned to the
You can configure a
port in access mode and specify the VLAN to carry the traffic for that
interface. If you do not configure the VLAN for a port in access mode, or an
access port, the interface carries the traffic for the default VLAN, which is
VLAN 1. You can change the access port membership in a VLAN by configuring the
VLAN. You must create the VLAN before you can assign it as an access VLAN for
an access port. If you change the access VLAN on an access port to a VLAN that
is not yet created, the UCS Manager shuts down that access port.
If an access port
receives a packet with an 802.1Q tag in the header other than the access VLAN
value, that port drops the packet without learning its MAC source address. If
you assign an access VLAN that is also a primary VLAN for a private VLAN, all
access ports with that access VLAN receives all the broadcast traffic for the
primary VLAN in the private VLAN mode.
Trunk Ports on a Cisco
Trunk ports allow
multiple VLANs to transport between switches over that trunk link. A trunk port
can carry untagged packets simultaneously with the 802.1Q tagged packets. When
you assign a default port VLAN ID to the trunk port, all untagged traffic
travels on the default port VLAN ID for the trunk port, and all untagged
traffic is assumed to belong to this VLAN. This VLAN is referred to as the
native VLAN ID for a trunk port. The native VLAN ID is the VLAN that carries
untagged traffic on trunk ports.
The trunk port sends
an egressing packet with a VLAN that is equal to the default port VLAN ID as
untagged; all the other egressing packets are tagged by the trunk port. If you
do not configure a native VLAN ID, the trunk port uses the default VLAN.
Changing the native VLAN on a trunk port, or an access VLAN of an
access port flaps the switch interface.