Re: IP Alias with iptables

[Antony Stone <Antony@Soft-Solutions.co.uk>]

On Tuesday 20 April 2004 4:08 am, Rodrigo Haces wrote:

> New Situation:
>
> eth0: 192.168.1.1 Connected to hub 1
> eth1: 192.168.0.1 Connected to hub 2
>
> hub 1 is for guests
> hub 2 is for administrative porposes, and MUST be able to use network
> 192.168.0.x and 192.168.1.x

So, the firewall needs to allow 192.168.1.0/24 addresses to connect to 
192.168.0.0/24 but not the other way round.

> so this is something i thought.
>
> eth0... 192.168.1.1 netmask 255.255.255.0
> eth1... 192.168.0.1 netmask 255.255.0.0

Doesn't look good.

> eth1:1. 192.168.1.101 netmask 255.255.0.0

Looks as bad as the first idea, with only one interface.

> my laptop is part of the administrative sector, i have 192.168.0.10 ip, but
> i need to be able to use also 192.168.1.10 so i can monitor guests,

What is wrong with yur laptop havign just one IP address (that *is* 
conventional, after all), and the firewall allowing it to "monitor" addresses 
in the other subnet?   Perhaps you should explain more about what you mean by 
"monitor"?

> Any ideas

Yes.   Have two subnets with separate address ranges, a firewall in between, 
and allow one subnet to connect to the other, but not the other way round.

eg:
eth0 192.168.1.1 netmask 255.255.255.0
eth1 192.168.0.1 netmask 255.255.255.0

iptables -P FORWARD DROP
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

Regards,

Antony.

-- 
Success is a lousy teacher.  It seduces smart people into thinking they can't 
lose.

 - William H Gates III

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