[CentOS] Static routing on CentOS

Cretu Adrian adycrt at gmail.com
Wed Feb 26 14:09:38 UTC 2014


Hi,
You can not have a gateway that is on another ip subnet than your physical
interfaces from that server, so a route should have a gateway that is on
the same ip subnet as your interfaces.
In your case you should add another subnet on both servers something like:
HOST A: 172.29.120.2
HOST B: 172.29.120.3

And then add a route for 20.20.20.0 via 172.29.120.3.

Or you can just add on either of the servers one more ip address from the
class of the other server.
All this will work if the servers are on the same broadcast domain (
http://en.wikipedia.org/wiki/Broadcast_domain) if they are on distinct ones
then you need to configure the router between them to route the
20.20.20.0/24 network to host b.






On Wed, Feb 26, 2014 at 8:28 AM, Jatin Davey <jashokda at cisco.com> wrote:

> Hi All
>
> I have two hosts. Host A and Host B
>
> Host A routing table
> ------------------------
> [root at localhost ~]# route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> 172.29.110.0    172.29.109.1    255.255.255.0   UG    0 0        0 eth0
> 172.29.109.0    0.0.0.0         255.255.255.0   U     0 0        0 eth0
> 169.254.0.0     0.0.0.0         255.255.0.0     U     0 0        0 eth0
> 0.0.0.0         172.29.109.1    0.0.0.0         UG    0 0        0 eth0
>
> HOST A IP address : 172.29.109.254
>
>
>
> Host B routing table
> -------------------------
> [jatin at localhost ~]$ route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> 172.29.110.0    0.0.0.0         255.255.255.0   U     1 0        0 eth0
> 20.20.20.0      0.0.0.0         255.255.255.0   U     0 0        0 eth0
> 169.254.0.0     0.0.0.0         255.255.0.0     U     1002 0        0 eth0
> 0.0.0.0         172.29.110.1    0.0.0.0         UG    0 0        0 eth0
>
> HOST B Ip address : 172.29.110.93
>
>
> Host B basically houses some simulated devices which are configured in
> the ip address range of 20.20.20.1 to 20.20.20.254. The netmask being
> used here is 255.255.255.0
>
> I want to configure a static route on HOST A so that they can reach the
> simulated devices running on HOST B which are in the ip address range
> 20.20.20.1-20.20.20.254 , I am trying the following command but it does
> not configure the static route for me.
>
> [root at localhost ~]# route add -net 20.20.20.0 netmask 255.255.255.0 gw
> 172.29.110.93
> SIOCADDRT: Network is unreachable
>
>
> Any help is greatly appreciated.
>
> Thanks
> Jatin
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