Creating a new router under a existing lan

rgto · 06-19-2015, 06:08 AM

Hello there! First of all I need to show my environment, this is my LAN:

Code:

[root@Server1 ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.28.0       0.0.0.0         255.255.252.0   U     0      0        0 eth0
link-local      0.0.0.0         255.255.0.0     U     0      0        0 eth0
default         10.0.28.1       0.0.0.0         UG    0      0        0 eth0
[root@brasilia ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:14:5F:33:2E:87
          inet addr:10.0.28.5  Bcast:10.0.31.255  Mask:255.255.252.0
...

Into this LAN, I've created a new CentOS7 server to make a new subnet 192.168.128.0/22 under this 10.0.28.0/22. I need do this new subnet clients (eg. a PC setted to 192.168.128.20/22) communicate with 10.0.28.0/22 LAN, and inverse the same. I need both LANs communicate between themself.

At this new CentOS7 server, I have enp0s3 (ethernet1) with IP 10.0.31.200/22 and enp0s8 (ethernet2) with IP 192.168.128.1/22 setted. This CentOS7 server looked like this:

Code:

[root@CentOS7 ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.28.5       0.0.0.0         UG    1024   0        0 enp0s3
10.0.28.0       0.0.0.0         255.255.252.0   U     0      0        0 enp0s3
192.168.128.0   0.0.0.0         255.255.252.0   U     0      0        0 enp0s8

I've done "echo 1 > /proc/sys/net/ipv4/ip_forward", then my PC 192.168.128.20 now can ping 10.0.31.200 and 192.168.120.20, but I can't reach any other computer from 10.0.28.* and who is on 10.0.28.* can't reach any computer into 192.168.128.*!

What I need to do? Thanks!

wildwizard · 06-19-2015, 06:17 AM

Quote:

Originally Posted by rgto

At this new CentOS7 server, I have enp0s3 (ethernet1) with IP 10.0.31.200/22 and enp0s8 (ethernet2) with IP 192.168.128.1/22 setted. This CentOS7 server looked like this:

Code:

[root@CentOS7 ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         10.0.28.5       0.0.0.0         UG    1024   0        0 enp0s3
10.0.28.0       0.0.0.0         255.255.252.0   U     0      0        0 enp0s3
192.168.120.0   0.0.0.0         255.255.252.0   U     0      0        0 enp0s8

See the highlighted part of your post that I have quoted?

Is one of those a typo in your post here or have you actually got them wrong on the system, as those don't match.

rgto · 06-19-2015, 07:21 AM

Oh I'm sorry, I typed wrong here, the correct is 192.168.128.0 where you mentioned. I'll fix it here.

But the problem is the same. One thing I forgot to mention: if i'm in this new CentOS7 system, I can ping both subnets.

wildwizard · 06-21-2015, 03:30 AM

Ok so the machine in the middle can see both networks ok?

Once you have a yes to that move on ....

Q. How do machines on each network know how to get to the other network?
A. Via routing tables

A shortcut is to add a fixed route on the default gateway device on each network pointing back to the machine in the middle
The long way is to do the same to each machine on the network