IBM SC30-3681-08 manual Frame Forwarding over the Frame Relay Network, Protocol Addresses

Using Frame Relay

Frame Forwarding over the Frame Relay Network

When the FR protocol receives a packet for encapsulation, it compares the packet's network address to the entries in the Address resolution Protocol (ARP) cache. If the ARP cache contains the DLCI number that matches the network address, the FR protocol encapsulates that packet into a frame and transmits the frame over its speci®ed local DLCI. If the ARP cache does not contain a match, the FR protocol sends out an ARP request over all con®gured PVCs on the interface. When the appropriate end-point responds with an ARP response, the FR protocol adds its local DLCI that received the ARP response to the ARP cache. Subsequent data packets directed to the same network address are then encapsulated into a frame and sent out over its local DLCI.

Protocol Addresses
	Protocol addresses can be either mapped statically to FR network PVC addresses
	or SVCs using locally con®gured names or discovered dynamically through Inverse
	ARP or ARP. (For more information on ARP and Inverse ARP, see the Protocol
	Con®guration and Monitoring Reference.) Either method is protocol-dependent as
	illustrated in Table 55.
	Note: Static protocol addresses are also referred to as static ARP entries. A static
	ARP entry is added to the con®guration with theadd protocol-address
	command.
	Table 55. Protocol Address Mapping
				VC Con®gured at
		ARP and Inverse		Protocol
	Protocol Type	ARP Usage	Static Mapping	Con®guration
	AP2	Yes	Yes	No
	IP	Yes	Yes	No
	IPX	Yes	Yes	No
	Banyan VINES**	No	No	No
	DNA IV	Yes	Yes	No
	OSI*, **	No	No	Yes
	* You must con®gure OSI at the protocol level to map the protocol address to the FR PVC.
	** Not supported using SVCs.

Multicast Emulation and Protocol Broadcast

Multicast emulation is an optional feature that allows protocols requiring multicast such as ARP to function properly over the FR interface. With multicast emulation, a multicast frame is transmitted on each active PVC. By using the enable and disable multicast commands, you can turn this feature on or off. Protocols that utilize multicast are AP2, ARP, Banyan VINES, DNA4, IP, and IPX.

Protocol broadcast is another optional feature that allows the IP RIP protocol to function properly over the FR interface. By using the enable protocol-broadcastand disable protocol-broadcastcommands, you can turn this feature on or off.

For protocols that support ARP/InARP over Frame Relay, Frame Relay will only multicast a protocols packets over a circuit if a protocol address was either learned or con®gured for that circuit.

394MRS V3.2 Software User's Guide