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Managing Switches
Configuration
VLANs make large networks more manageable. You can group users
according to some shared characteristic, such as a common business
function or a common protocol. A single switch may have several
independent VLANs within it.
Note: VLANs must be created with the device console.
Configuration - Device Features
The Device Features page (only found on switches) lets you set some or all
of these features:
■ Automatic Broadcast Control (ABC)
■ Multicast Filtering (IGMP)
■ Spanning Tree
Automatic Broadcast Control (ABC)
Automatic Broadcast Control (ABC) is a feature that controls broadcasts
through IP/IPX Broadcast Reduction. IP/IPX Broadcast Reduction reduces
the number of broadcasts propagated through the network.
Using ABC, the switch acts as a proxy server, replying to Address Resolution
Protocol (ARP) requests, Nearest Server Query (NSQ) requests, and
GetLocalTarget requests on behalf of the destination node. An ARP cache
(learned address table) is created for each subnet allowing the switch to
proxy reply with the resolved MAC address instead of forwarding the
requests out all ports. This limits the broadcasts within the switching
domain. The Service Advertising Protocol (SAP) table performs the same
function in an IPX network. By using these tables, the switch can resolve
addresses for any node in the network that it already knows about.
Routing Information Protocol. The switch also intercepts Routing
Information Protocol (RIP) and SAP broadcasts and forwards these only to
ports where routers and servers have been detected. This also reduces the
number of broadcasts on the network.
For example, if User A sends out a broadcast message to connect to its
server, the request is sent out of all ports on the switch. When the server
responds to User A, the switch intercepts the response and learns that the
server is on that port. When User B sends a request to the same server, the
switch already knows which port that server is on and sends that
information to User B, just as if the server had responded to the request.
User B’s request is not broadcast out any of the switch ports.
Managing Switches
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