Invalidating ARP Caches


Jon Crowcroft (jon@Cs.Ucl.AC.UK)
Mon, 1 Jun 87 15:51:14 GMT-0:00


I have only had one answer on how to invalidate arp caches in
hosts when i move my IP (proxy arp) subnet router, so here's my
thoughts...

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Could call this NARP (not arp):

I am considering writing a service that listens for IP broadcasts
(multicasts when available) and invalidates arp caches on basis
of these. When (before/after) a router moves, it will still
forward these packets so sitting on any host I can (hopefully
only with certain privilages) say:

arpinval {ip addr}*

which will broadcast some packet like

IP header with NARP type + <IP Addr Addr etc)

(has to be IP broadcast, not lower level or the IP subnet routers wont
forward it). When routers get clever, they could send this
packet for me.

Any reason not to do this, apart from the obvious possible
misuses and broadcast traffic (though only one broadcast to fix
a lot of hosts)?

jon



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