HP TopTools for Hubs and Switches - Manual (Page 74)

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Group Policies
Advanced Switch Features
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.
Enabling Broadcast Control for IP
The IP protocol uses Address Resolution Protocol (ARP) packets to find the
MAC address of a node that corresponds to the network layer address. When
Broadcast Control is enabled, the switch intercepts the ARP packet on its way
to the destination node. If this destination is unknown to the switch, the switch
floods the ARP request to all ports. When the destination port responds, the
switch stores information about the source and destination MAC addresses
and layer 3 addresses in its ARP cache. This information allows the switch to
proxy a reply containing the MAC address of a destination to the source of an
ARP request. The source can then send a unicast packet directly to the
destination. The amount of broadcast traffic has been decreased.
Automatic IP RIP Control
To further reduce broadcast traffic, you can check Automatic IP RIP Control.
IP RIP packets are sent out periodically (every 30 seconds) to distribute
routing information. By enabling Automatic IP RIP Control, the switch will
only forward RIP packets out the ports on which RIP packets have been
received. Since routers are the only devices that generate RIP packets, this
ensures that RIP packets are only sent out ports with routers attached to them.
When this feature is not enabled, IP RIP packets are forwarded to all ports.
Enabling Broadcast Control for IPX
The IPX protocol broadcasts all of its known routes and services every minute
by using IPX, RIP and Service Advertising Protocol (SAP) packets. When
servers are booted up, they advertise their services using SAP. These frames
must be forwarded by routers, which maintain a database of this information,
allowing clients on the network to obtain the internetwork addresses of the
servers where they can access services.