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SubjectRe: [2.2] Network Interface aliasing
On Tue, 9 Nov 1999, Alan Cox wrote:

> > (255.255.255.255) but further investigation shows that this server
> > will respond (incorrectly) to an ARP. It's my understanding that
> > loopbacks should not respond to ARP requests. We've also tried adding
> > the -arp when aliasing the loopback to no avail.
>
> Loopbacks dont respond to arp. The ethernet interfaces however will respond
> to arps for an address belonging to that machine



Make sure your are not tcpdumping on the machine in question.
If you put an interface in PROMISC mode, it will answer any packets to
any IP it thinks it has holds...



Example, machines A,B,C all have the same IP on a lookback or
dummy interface. A load director/etc is currently routing all traffic
to the cluster IP to machine A.

Should machine Bs interface get into PROMISC mode all packets
(even though they are sent to another MAC addr) will hit the IP layer,
and should the IP be found on a local interface, the machine will
respond.


Sooo, should you be running multiple machines sharing an IP
for any reason *make sure* none of the cards are in PROMISC mode, or
things will break down quickly.

---
As folks might have suspected, not much survives except roaches,
and they don't carry large enough packets fast enough...
--About the Internet and nuclear war.



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