Re: How does arp work with NAT?

Peter 'Luna' Runestig (peter+linux-kernel@runestig.com)
Thu, 26 Aug 1999 09:31:46 +0200


----- Original Message -----
From: <kuznet@ms2.inr.ac.ru>
To: Peter 'Luna' Runestig <peter+linux-kernel@runestig.COM>
Cc: <linux-kernel@vger.rutgers.edu>
Sent: den 25 augusti 1999 17:16
Subject: Re: How does arp work with NAT?

!!! First I must correct myself: Of cource my firewall has two nics! In my
original post, it seemed it only had one. This is the correct nic config:

eth0 133.20.12.67
eth0:0 133.20.12.68
eth1 192.168.71.201

> Hello!
>
> > 0:60:97:15:41:48 ff:ff:ff:ff:ff:ff 0806 60: arp who-has 133.20.12.20 \
> > tell 133.20.12.67
> > ^^
> ...
> > It seems that the arp "source address" isn't NAT'ed. Is it supposed to
be, or isn't things
> > designed that way?
>
> BTW I see no rules to translate/masquerade this address in your setup,
> so that it is difficult to understand your question.

Hmm... isn't this the translating rule:

[root@fd_router /]# ip rule
<snip>
32025: from 192.168.71.33 lookup main map-to 133.20.12.68
<snip>

What I (also) forgot to include in my original post:

[root@fd_router /]# ip route list table local
<snip>
nat 133.20.12.68 via 192.168.71.33 scope host
<snip>

> Generally, ARP requests are sent with "source" address of the packet which
> hits wire, (provided you did not break kernel with some of patches
floating
> here). Do you see? It is translated by definition.

No, I'm afraid I lost you here... But according to Matthew G. Marsh
<mgm@paktronix.com>, the arp request was correctly send with the nic's
primary address as source address.

> Alexey Kuznetsov

Cheers,
Peter

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