Ubuntu - how to ignore dns and default route on all but one?

dns default route

credit

  • https://serverfault.com/questions/674731/multiple-dhcp-uplinks-how-to-ignore-dns-and-default-route-on-all-but-one
  • https://serverfault.com/a/674738

(I am still interested in solutions that only touch /etc/network/interfaces{,.d/}, but not /etc/dhcp/. In the absence of such solutions, I use this one.)

In /etc/dhcp*/dhclient.conf, remove the options routers, domain-name-servers, domain-name, domain-search from the global request statement. Then add this (assuming eth0 is the device where default route and DNS shall not get ignored):

interface "eth0" {
    also request routers, domain-name-servers, domain-name, domain-search;
}

This solution works at least for isc-dhcp-client version 4.2.2.dfsg.1-5+deb70u8 as it is shipped with Debian 7. I assume it works for later versions too.

Edit:

Confirmed that the original idea works with minor changes (eth0 must be quoted, and it should be request, not required) Specified the dlclient version this works for