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

Linux Advanced Routing and Traffic Control

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At 02:36 AM 2/11/2001 -0200, Rogerio Brito wrote:
On Feb 10 2001, bert hubert wrote:
> You can, I think, but you need to be very sure that your NAT machine
> isn't sending out any ICMP Redirects.

        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.

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, danb@xxxxxxxxxxxxxxxxxxxx




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