HP J3250M manual Enabling Broadcast Control for IPX, Automatic IP Gateway Configuration

Managing Switches

Configuration

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.

Automatic IPX RIP/SAP Control. To further reduce network traffic, you can check the Automatic IPX RIP/SAP Control check box. The switch will intercept RIPs and SAPs, broadcasting them only to ports where IPX routers or servers have been detected, or to ports that have been configured to transmit RIPs or SAPs. When this feature is not enabled, IPX RIP/SAP packets are forwarded to all ports.

Automatic IP Gateway Configuration

When Automatic IP Gateway Configuration is enabled, the switch will modify replies from the DHCP server so that the Default Gateway IP address of client becomes the client’s own IP address. This is useful in a multinetted

Managing Switches

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