El vie, 10 de 09 de 2004 a las 05:10, John Black escribiÃ: > How does assigning alias IP address work? > > I have one network jack coming into my server room. > eth0 10.10.10.10 > > I have two servers with public IP address. > this assigns them, right? > ifconfig eth0:10 192.168.1.10 netmask 255.255.255.0 > ifconfig eth0:11 192.168.2.11 netmask 255.255.255.0 > > iptables -t nat -A PREROUTING -d 192.168.1.10 -i eth0 \ > -j DNAT --to-destination 10.10.10.11 > iptables -t nat -A PREROUTING -d 192.168.2.11 -i eth0 \ > -j DNAT --to-destination 10.10.10.12 > > When a mail or web request is made from the internet. > How does it know where the servers are? > > thanks > John The new kernel networking code named iproute2 doesn't make any differences between IPs assigned to an interfaces or aliased IPs. You can assign any number of IPs to an interface, and this can be primary IPs or secundary IPs, but for the kernel it's just another IP assigned to the machine (really it's more complex, the IPs are assigned to services, not any hardware in particular). So when a request is made from the internet the routing code just looks in it's tables what routes it have to use, and as the IPs are assigned to the same machine it sends the request to the machine you have assigned the IPs. -- Jose Maria Lopez Hernandez Director Tecnico de bgSEC jkerouac@xxxxxxxxx bgSEC Seguridad y Consultoria de Sistemas Informaticos http://www.bgsec.com ESPAÃA The only people for me are the mad ones -- the ones who are mad to live, mad to talk, mad to be saved, desirous of everything at the same time, the ones who never yawn or say a commonplace thing, but burn, burn, burn like fabulous yellow Roman candles. -- Jack Kerouac, "On the Road"
