Allied Telesis AT-S63 - Manual (Page 91)

AT-S63 Management Software Menus Interface User’s Guide
Section I: Basic Operations 91
Common VLAN When a master switch searches for the other switches in an enhanced
stack, it sends out a broadcast packet out a local subnet. (The designation
of the subnet is explained in “Master Switch and Local Interface,” next.)
Since a broadcast packet cannot cross a router or a VLAN boundary, the
switches of a stack must be connected together with a common VLAN.
The VLAN acts as the transfer path for the broadcast packets from the
master switch to the slave switches and also serves as the path for other
management packets.
Here are a couple things to keep in mind as you plan the common VLAN
for your enhanced stack:
ˆ Any valid VLAN name and VLAN identifier (VID) can be used for the
common VLAN, but it should be the same on all the switches in the
stack.
ˆ A slave switch of an enhanced stack can be indirectly connected to the
master switch through other switches, provided there is an
uninterrupted path of the common VLAN from a slave switch to the
master switch.
ˆ The Default_VLAN can be used as the common VLAN.
ˆ The common VLAN does not have to be dedicated solely to the
enhanced stacking feature.
For background information on port-based and tagged virtual LANs, refer
to “VLAN Overview” on page 590.
Master Switch
and Local
Interface
Before a switch can function as the master switch of an enhanced stack, it
needs to know which subnet is acting as the common subnet among the
switches in the stack. After it has that information, it can begin to monitor
that subnet for the management packets from the other switches and from
remote management workstations. Knowing the common subnet, it will
also know which subnet to send out the broadcast packets when
searching for the switches in the stack.
This process involves creating a routing interface on the master switch on
the common subnet and designating it as the local interface. The concept
of routing interfaces first appeared in the AT-9400 Series switches with the
introduction of Layer 3 routing on the device and the implementation of
static routing and the Routing Information Protocol (RIP) version 1 and 2.
An interface represents a logical connection to a network or subnet local to
the switch for purposes of routing packets. To configure an interface, you
assign it an IP address and subnet mask appropriate to the subnet where
it will route packets, and add it to the VLAN that contains the subnet.