[CentOS] Gateway question

Tue Aug 9 07:58:40 UTC 2016
Levente Birta <blevi.linux at gmail.com>

On 09/08/2016 06:56, Anthony K wrote:
> On 08/08/16 21:05, Levente Birta wrote:
>> But how can I add achieve this only with ip route command ... without
>> route?
>> Can I add this in any config files (ex: route-enp2s0)?
> Hi Levente.
> The iproute2 man page for each command is rather well documented on
> CentOS 7.  For instance, to view the specifics of *ip route*, type *man
> ip-route*.  On older versions of CentOS, all commands to ip have been
> lumped into *m**an ip*.
> Also, would you care to explain why you'd want to have the same subnet
> on 2 interfaces of the same device?  If both networks had a host with
> the same IP, and another host on either one of the networks needed to
> talk to one of them, how would the router know which one to talk to?
> I have encountered this before where one company acquired another and
> they both had same subnet IP's.  Before we renumbered one of the
> subnets, we resolved this via iptables mungling and policy routing.  So,
> it's doable, but why when there's plentiful supply of RFC1918 IP addresses?

As I said in the initial message the centos box need to access the 
internet on both interfaces, the gateway in function of source IP ( the 
two IPs allocated on the centos box on two interfaces ) route the 
traffic on different WAN connection.

My problem simply is that on the Centos box I cannot access the internet 
on the second interface (i.e. second WAN connection) without the 
command: #route add default gw dev enp3s0

I'd like to mention that any traffic on the LAN is going in/out on the 
right interface ... just the internet cannot be reached on the second 

What I don't understand why the route command allow to add a second 
default gateway with different interface, but the ip route command doesn't?