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38 Chapter2
Networking Concepts
Address Resolution
Probe and Probe Proxy
NS 3000 LAN, 100VG-AnyLAN, and 100Base-T NIs with the
IEEE 802.3 protocol enabled are able to make use of a proprietary HP
protocol called probe. Probe makes it possible for nodes on an NS
IEEE 802.3 LAN, 100VG-AnyLAN, and 100Base-T to communicate
without a network directory or domain names. A node can determine
connection information about a node on the same LAN by sending a
multicast probe request out on the network. The target node recognizes
its address in the probe request and sends an individually addressed
probe reply with the necessary connection information to the
requesting node. The probe request/reply mechanism is sufficient to
obtain connection requirements within a network.
If the nodes on that LAN are to communicate with other networks, at
least one node on the network must have a network directory. The node
with the network directory is called a proxy server. By using the
probe protocol, a node without a network directory can multicast a
request for an internet address from the proxy server. For backup
purposes, you should designate at least two nodes to be proxy servers.
Address Resolution Protocol (ARP)
HP e3000 LAN, Token Ring, FDDI, 100VG-AnyLAN, AND 100Base-T
NIs are able to make use of a standard protocol called Address
Resolution Protocol (ARP). ARP provides IP address to station address
resolution. ARP is enabled when the Ethernet protocol or Token Ring is
enabled.
Enabling Probe and ARP
With the concurrent configuration of IEEE 802.3 and Ethernet on a
network, both the probe and ARP protocols are also enabled. Both
protocols broadcast requests to all nodes on the network to resolve the
address of a given remote node.
If you disable IEEE 802.3 on a LAN NI, you also disable the probe
protocol. Likewise, by disabling Ethernet, you disable the ARP protocol
associated with it. You cannot disable both of these protocols
simultaneously; at least one must be active to facilitate network
communications.