Avaya P580 - Manual (Page 191)

Avaya P550R, P580, P880, and P882 Multiservice Switch User Guide, v5.3.1 5-11
Configuring Port Parameters
The following is an example of a problem with assigning more the
one VLAN to a port.
■
All PCs and Servers are connected to the Avaya Multiservice
Switch 10/100TX switch ports. The following configuring of
ports to VLANs are done with the Web Agent.
■
PC1 is a member of VLAN1 and is connect to switch Port 1
■
PC2 is a member of VLAN2 and is connected to switch Port 2
■
SERVER1 is a member of VLAN4 and is connected to switch
Port 4
With the set vlan CLI command, assign port 1, and port 2 to VLAN4
and also assign port 4 to VLAN1 and VLAN2. Then PC1 and PC2
could communicate with SERVER1 across VLANs without any
noticeable problems. However, when PC1 transmits a packet to
SERVER1, the following occurs:
■
The packet is sent to the Switch
■
The switch looks for the MAC address of SERVER1in the
Address Forwarding Table for VLAN1 (because this is the
actual port VLAN assigned to the port)
■
The switch will be unable to find an entry for the MAC
address of SERVER1
■
The switch will flood this packet to all ports assigned to
VLAN1 (regardless of how the VLAN was assigned to the
port)
* Note: The only exception to flooding a port is if
‘Known Mode’ is set to enable on the port,
which stops the flooding of destination
unknown unicast packets.
If you had many clients/servers on separate VLANs and they tried to
communicate over multiple VLANs using this method, you would
flood your network with undesired packets, thus slowing your
overall network performance. Currently, the best solution is to use a
L3 module to route between the VLANs. This would eliminate the
broadcast of destination unknown unicast packets.