On Wed, Apr 14, 1999 at 06:25:19PM -0700, [EMAIL PROTECTED] wrote:
> Bernd> Proxy ARP means: Answer ARP requests for IP Addresses which are not
> Bernd> local to you. For example a PPP Server will answer for ARP requsts for
> Bernd> one of its clients. This means all servers in a network whith a dial-in
> Bernd> server can talk to the PPP clients without knowing, that they are
> Bernd> "behind" the PPP router.
>
> Bernd> Gratious ARP means: request you own address just to inform all hosts on
> Bernd> the same wire about your new/changed address.
>
> OK, I understand that the applications are different, but the resulting arp
> packet is the same, right? Basically, a host tells everyone on it's LAN to
> send packets destined for a particular IP address to it's MAC address.
No, since setting proxy arp with the arp command does not genrate any
packets. It just fills a table which will be used if a request is received.
In that case the response from the proxy arp table is unecessary, because as
mentioned above the host will anser requests for its addresses (all of them)
anyway.
> You mentioned something about answering SYNs. What was that about?
It was about detecting a failed server by observing the TCP session
establishments to it and do a failover if there are none within a given time
(e.g. 1sec). But its hard to do to make it stable.
> I am considering using "ifconfig -arp" to disable arp from the online
> server host, so that if/when it goes down, the failover host can do
> gratuitous arp. Are there any pitfals in doing this?
The primary server wont answer any ARP requests at all, therefore you will
have to run arp_send on it, too.
> Can I turn arp off for just the eth0:1 alias, and leave it on for the
> eth0 device?
Well, you mean turn off sending arp resposnes for the address assigned to
eth0:1, i guess. (Since the reqests are always recieved via eth0 and send
via eth0 its the only �real� device). This is not possible as far as I know.
But you can "hardcode" the HW addresses in the router for the eth0 addresses
of the both hosts.
Greetings
Bernd
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