Configuring Virtual LANs (VLANs)
December 2000 25 - 55
Figure 25.21 VLAN list on Foundry Stackable Layer 2 Switch
As shown in this example, the MAC VLAN list contains four entries. For simplicity, each of the MAC addresses in
the list in this example belongs to a host attached to the switch. Each of the MAC addresses belongs to a host
attached to the switch port indicated in the file. When the switch receives a packet from one of the MAC
addresses, the packet matches an entry in the MAC VLAN list. When this occurs, the switch adds the packet to
VLAN specified in the MAC VLAN entry. Moreover, of the output port for the packet is a tagged port, the switch
adds the four-byte tag field to the end of the packet thus tagging the packet.
NOTE: If the switch receives a packet with a source MAC address that is contained in the MAC VLAN list, but
that switch receives that packet on a different port than the one specified in the MAC VLAN list, the packet does
not match the list and is switched normally. The MAC VLAN switching described in this section is not performed
for the packet.
In this example, suppose host 1145.5563.a101 sends a packet destined for a host on the router attached to port
10. The switch compares the packet’s source MAC address and input port against the entries in the MAC VLAN
field and finds a match. The switch then assigns that packet to the VLAN indicated in the MAC VLAN file. In this
case, the VLAN ID is 10. Since the packet’s destination is reached through switch port 10, a tagged port, the
switch also adds the tag to the packet before placing the packet in the output queue on port 10. The MAC VLAN
list does not specify a priority for the packet, so the switch uses the priority associated with the port. In this case,
the priority is normal so the switch places the packet in the normal priority queue.
If the switch receives a packet from host 1145.5563.C11f on port 4, the switch assigns the packet to VLAN 20 and
places the packet in the high priority queue of its output port. If the output port is tagged, the switch also adds the
tag to the packet.
Configuring a MAC VLAN List
To configure the MAC VLAN list:
1. Create a new text file. For convenience, you might want to create the text file on the TFTP server from which
the switch will download the MAC VLAN list. Otherwise, you can copy the file onto the TFTP server after you
add the commands to the file.
Server
Link
Activity
FDX
Link/Act
FDX
Link/Act
FDX
Link/Act
FDX
Link/Act
Link
Activity
Power
Console
FastIron Multilayer
Router
1145.5563.a101
1145.5563.a102
e4
1145.5563.c11f
MAC VLAN File:
Source MAC, VLAN ID, input port, priority
ext mac-vlan 145.5563.a101 10 ethernet 1
ext mac-vlan 145.5563.a102 10 1
ext mac-vlan 145.5563.a103 20 4
ext mac-vlan 145.5563.c11f 20 4 priority high
ethernet
ethernet
ethernet
1145.5563.a103
e10
e1
Ports e1 - e9 are untagged.
Port e10 is tagged.
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