Preventing ICMP Redirects? (was: Re: [LARTC] HTTP only works on second try from doublely NAT'ed wi

Preventing ICMP Redirects? (was: Re: [LARTC] HTTP only works on second try from doublely NAT'ed wi

[Rogerio]

<PRE>On Feb 10 2001, bert hubert wrote:
&gt;<i> You can, I think, but you need to be very sure that your NAT machine
</I>&gt;<i> isn't sending out any ICMP Redirects.
</I>
	I've been bitten by these ICMP Redirects once. Is there any
	way to prevent them from being sent out? Perhaps doing some
	packet filtering of the ICMP Redirects? Even if this works,
	this sure sounds like a dirty solution... :-(

	In that occasion, I was trying to set up a masquerading box
	with only one NIC and two IP addresses (the Internet-valid one
	and the private one), hooking everything in a single hub and
	routing accordingly.

	I don't remember the details (since this was many months ago),
	but the only solution that I could make work was to buy
	another NIC for the masquerading box and put one IP in each
	NIC, doing everything as usual. :-(

	As I don't remember more details of the situation, I'm just
	hoping that this description rings a bell for someone. Any
	explanation of how to make this setup with just one NIC or
	comments on why this shouldn't be done are immensely
	appreciated.


	Thanks in advance, Roger...

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-  Rogerio Brito - <A HREF="mailto:rbrito@iname.com">rbrito@iname.com</A> - <A HREF="http://www.ime.usp.br/~rbrito/">http://www.ime.usp.br/~rbrito/</A>
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

</PRE>

Preventing ICMP Redirects? (was: Re: [LARTC] HTTP only

[Dan]

<PRE>At 02:36 AM 2/11/2001 -0200, Rogerio Brito wrote:
&gt;<i>On Feb 10 2001, bert hubert wrote:
</I>&gt;<i> &gt; You can, I think, but you need to be very sure that your NAT machine
</I>&gt;<i> &gt; isn't sending out any ICMP Redirects.
</I>&gt;<i>
</I>&gt;<i>         I've been bitten by these ICMP Redirects once. Is there any
</I>&gt;<i>         way to prevent them from being sent out? Perhaps doing some
</I>&gt;<i>         packet filtering of the ICMP Redirects? Even if this works,
</I>&gt;<i>         this sure sounds like a dirty solution... :-(
</I>&gt;<i>
</I>&gt;<i>         In that occasion, I was trying to set up a masquerading box
</I>&gt;<i>         with only one NIC and two IP addresses (the Internet-valid one
</I>&gt;<i>         and the private one), hooking everything in a single hub and
</I>&gt;<i>         routing accordingly.
</I>&gt;<i>
</I>&gt;<i>         I don't remember the details (since this was many months ago),
</I>&gt;<i>         but the only solution that I could make work was to buy
</I>&gt;<i>         another NIC for the masquerading box and put one IP in each
</I>&gt;<i>         NIC, doing everything as usual. :-(
</I>&gt;<i>
</I>&gt;<i>         As I don't remember more details of the situation, I'm just
</I>&gt;<i>         hoping that this description rings a bell for someone. Any
</I>&gt;<i>         explanation of how to make this setup with just one NIC or
</I>&gt;<i>         comments on why this shouldn't be done are immensely
</I>&gt;<i>         appreciated.
</I>
Even when you correctly aliased your single NIC to act like two interfaces?

eth0:0  routable ip / external (seperate) subnet
eth1:1 local ip / local subnet

I've done what you described using aliasing a couple of times and I never 
got bit by ICMP redirects (like I did this last time).

Now I kind of wish I would have fixed the ICMP redirect problem instead of 
just changing subnets.  :-)

Dan Browning, Cyclone Computer Systems, <A HREF="mailto:danb@cyclonecomputers.com">danb@cyclonecomputers.com</A>



</PRE>