Re: firewalls for dummies?

[Erwann CORVELLEC <eco@guy-hoquet.net>]

Stuart Marshall wrote:
> The one test so far was set up as:
> 
>  upstream router ------ firewall -- switched_hub ---- local_machine_a
>  X.Y.116.254            ^      ^
>  X.Y.12.254 (alias)     |      |
>                         |      |
>         eth0 = X.Y.12.2 |      |_ eth1 = X.Y.12.242
> 
> Here local_machine_a was configured as:
> 
>         IPADDR=X.Y.12.107
>         NETMASK=255.255.255.0
>         NETWORK=X.Y.12.0
>         BROADCAST=X.Y.12.255
>         GATEWAY=X.Y.12.242
> 
> I put a "1" into /proc/sys/net/ipv4/ip_forward and set the chain
> policies all to ACCEPT hoping to create a simple pass-through system.
> No bytes would go from the inside to the outside or the other way round.

  You have to setup proxy arp. Watch kernel docs but that should do it:
echo 1 > /proc/sys/net/ipv4/conf/eth0/proxy_arp
echo 1 > /proc/sys/net/ipv4/conf/eth1/proxy_arp

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  ECO.  | Hiroshima 45 -> Tchernobyl 86 -> Window$ 00 |
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