Alcatel Carrier Internetworking Solutions Switch/Router Manuale Utente

Page 22-9

In release 2.1 and later, AutoTracker’s 

VLAN

 port policy can be set to operate in either of two 

distinct modes:

• In the original mode, wherein membership in all 

VLAN

s active on a port is inherited by all 

• In a new mode, wherein membership in all 

VLAN

s active on a port 

 

 inherited by all 

devices connected to that port. This is the current, default functionality with which the 
switch ships. Current port policy functionality is explained on page 22-11.

Port policy functionality is set on a switch-wide basis, via a flag in the switch’s 

 file 

called 

. The switch ships with port policy functionality set to operate in the new 

mode. You can revert the switch to original port policy functionality by editing the file and 
setting the 

 flag to 1. You must then restart the switch. (The file is accessed, and 

can be edited, via the switch User Interface. You can view the current setting of 

 

with the 

 

 command. See Chapter 7, “Managing Files,” for information on editing 

the 

 file.)

Port policies can cause problems in a multi-switch environment. AutoTracker assumes that 
each switch in a multi-switch environment can independently arrive at identical 

VLAN

 assign-

ments for all devices in the network. This is not true when port policies are in effect because 
of their very nature: port policies are switch-specific and not network wide. The figure on 
page 22-10, which explains original port policy functionality, provides an example of how 
port policies can result in inconsistent 

VLAN

 membership between two switches – notice the 

inconsistent 

VLAN

 membership in Omni Switch/Router 1 and in Omni Switch/Router 2.

The use of port policies in a multi-switch environment can result in connectivity problems if 
the source switch and the destination switch are separated by other switches. The switches 
along the path of the frame will not have identical 

VLAN

 memberships. At any particular 

switch along the path, frames could be lost because of inconsistencies in the 

VLAN

 member-

ship of the frames’ source and destination devices. 

In addition, AutoTracker maintains devices in the same 

VLAN

 without regard to the devices’ 

location – provided the devices match the same AutoTracker policies throughout the network. 
Multiple switches will assign a device to the same 

VLAN

s provided that device matches the 

same policies on each switch. This is not possible when port policies are in effect because, as 
stated, by their very nature port policies are switch-specific and not network-wide. 

For these reasons, the Omni Switch/Router now ships with new port policy functionality 
(although, as explained, you can revert the switch to original port policy functionality if you 
wish). The new functionality still enables users to assign ports to 

VLAN

s and still enables those 

ports to carry traffic for those 

VLAN

s. However, with the new functionality, port policies are 

not used to learn 

VLAN

In order for a device to be assigned to a 

VLAN

, it must match an existing logical policy of the 

VLAN

The following pages provide examples of original and current port policy functionality. The 
limitations of port policies become apparent if one tries to use port policies to create two 

VLAN

s in these sample networks, one for Devices A and B and one for Devices C and D.