2 grammes kai route tables

[I.Ioannou]

Exw se ena site 2 grammes : line1 kai line2, kai oi dyo bgainoun
Internet. To default getaway einai apo tin line1. To zitoumeno einai 
kapoios tropos wste an den antapokrinetai h line1 (kaki
syndesi, polla lost packets klp) aytomata na ginei default
getaway h line2. Isws kai me kapoio tropo na alaksoun ta
records tou DNS alla ayto einai 2reuon.
Kanei to routed gia ayta ? Kai an nai, exei kaneis kanena
sample config tetoias periptwsis ?

TIA
roryt