Allied Telesis AT-S63 User Manual

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Chapter 2: Enhanced Stacking
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Section I: Basic Operations
Master Switch and the 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. It uses that information to know which subnet to 
send out its broadcast packets and to monitor for the management 
packets from the other switches and from remote management 
workstations.
Designating the common VLAN and subnet 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 Switch with Layer 3 routing 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.
For the most part, routing interfaces are limited to the IPv4 packet routing 
feature and are unnecessary beyond that feature. There are, however, a 
few exceptions. One is the enhanced stacking feature. The rule is that the 
master switch of an enhanced stack must have at least one interface and 
the interface must be assigned to the common subnet that interconnects 
the switches of the stack. Furthermore, the interface must be designated 
as the switch’s local interface. The act of designating an interface as the 
local interface tells the switch which interface and which subnet it should 
use for the enhanced stacking feature.
For background information on the IPv4 routing feature, refer Chapter 27, 
“Internet Protocol Version 4 Packet Routing” on page 299.