Foundry NetIron M2404C and M2404F Metro Access Switches Configuring VLANs (Rev.03)
Virtual LANs
© 2008 Foundry Networks, Inc.
Page 6 of 73
If a port is defined as untagged on a certain VLAN and a tagged packet arrives at that port with the
correct VLAN, then the packet will be switched to that VLAN.
Each port has a default VLAN. If a packet with no VID arrives at a port, the packet will be
regarded as pertaining to the port default VLAN. If the port is not a member of the default VLAN
configured on it, all incoming untagged packets will be discarded.
NOTE
Packets arriving tagged with a VLAN ID that is not configured on a port will be
discarded.
Figure 2
is an example for the use of tagged VLANs. Several computers are connected to some
switches that are connected to Switch 4. If the direct communication between the users needs to be
denied, each user can be put on a different VLAN.
Figure 2: VLAN Tagging Example
Tagged VLANs on Link Aggregation Ports
Tagging is commonly used with the Link Aggregation feature. Tags enable multiple VLANs to
span multiple switches, using one or more aggregated links. In a port-based VLAN, some VLANs
can be configured on trunk ports, as shown in
Figure 3
. In this example all the connections up to
the Central Offices (COs) are Fast Ethernet. The capacity of the connection between the two COs
is increased by Link Aggregation. The connections to the User Networks represent users or hubs.
Each of the connections carries a different VLAN.
For more information about the Link Aggregation feature refer to “
Configuring Interfaces
”.