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[RedHat] ARP issue
04-12-2013
[RedHat] ARP issue
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arp(7P) arp(7P) NAME
arp - Address Resolution Protocol DESCRIPTION
ARP is a protocol used to dynamically map between DARPA Internet and hardware station addresses. It is used by all LAN drivers. ARP caches Internet-to-hardware station address mappings. When an interface requests a mapping for an address not in the cache, ARP queues the message that requires the mapping, and broadcasts a message on the associated network requesting the address mapping if the encapsula- tion method has been enabled for the interface. If a response is provided, the new mapping is cached and any pending message is transmit- ted. ARP queues at most one packet while waiting for a mapping request to be responded to; only the most recently ``transmitted'' packet is kept. To facilitate communications with systems that do not use ARP, calls are provided to enter and delete entries in the Internet-to-hardware station address tables. Application Usage: Each call takes the same structure as an argument. sets an ARP entry, gets an ARP entry, and deletes an ARP entry. These calls can be applied to any socket descriptor s, but only by the super-user. The structure contains: The address family for the must be for the it must be The only flag bits that can be written are and Fibre Channel hosts only support the flag. causes the entry to be permanent. specifies that the ARP code should respond to ARP requests for the indicated host coming from other machines. This allows a host to act as an ARP server, which may be useful in convincing an ARP-only machine to talk to a non-ARP machine. ARP watches passively for hosts impersonating the local host (i.e., a host that responds to an ARP mapping request for the local host's address). DIAGNOSTICS
This message printed on the console screen means that ARP has discovered another host on the local network that responds to mapping requests for its own Internet address. WARNINGS
To enable the encapsulation method, use the command (see ifconfig(1M)). AUTHOR
ARP was developed by the University of California, Berkeley. SEE ALSO
ifconfig(1M), inet(3N), lan(7), arp(1M). RFC826, Dave Plummer, Network Information Center, SRI. arp(7P)