[SOLVED] CentOS 7 as NAT Gateway - almost

taylorkh · 03-17-2017, 10:55 AM

Thanks again c0wb0y and lazydog.

I think my brain is in a loop. I decided to start over, use NetworkManager and figure out what it did. I reimaged my test PC with a snapshot from before I started messing with the network configuration. I enabled both NICs The wired NIC picked up 192.168.0.115 and the wireless 192.168.0.125. Everything seemed to work OK. I saved the state of things network thus

Code:

ifconfig > ifconfig.before
iptables-save > savedrules.before
cat /etc/sysctl.conf > sysctl.before
firewall-cmd --list-all-zones > zones.before
route -nv > route.before

I then edited the wired NIC using NetworkManager and changed it to "Shared with other computers." I saved the change, stopped and started the NIC and ran the above commands again - saving the results to .after files. ifconfig showed that the wired NIC was now on the 10.42.0 subnet

Code:

p1p2: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.42.0.1  netmask 255.255.255.0  broadcast 10.42.0.255

Using a utility called Beyond Compare (scootersoftware.com) I examined the other files. I found NO changes to sysctl nor to the zones. The routing table changed thus

Code:

Before
------
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    100    0        0 p1p2
0.0.0.0         192.168.0.1     0.0.0.0         UG    600    0        0 wlp2s0
192.168.0.0     0.0.0.0         255.255.255.0   U     100    0        0 p1p2
192.168.0.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp2s0

After
-----
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.0.1     0.0.0.0         UG    600    0        0 wlp2s0
10.42.0.0       0.0.0.0         255.255.255.0   U     100    0        0 p1p2
192.168.0.0     0.0.0.0         255.255.255.0   U     600    0        0 wlp2s0

Most of the changes were evident in the saved rules as shown in the attachment below.

This worked, it was EASY and I will keep the rules comparison for study. Time to move on to something else - like actually setting my network up this way - and perhaps setting up DHCP on the "router" PC to server the 10.42.0 subnet.

Again, thanks for your input.

Ken

Jjanel · 03-20-2017, 02:01 AM

Cool! You can mark this as 'Solved', via ThreadTools at top,
so future searchers will see that there's a Solution here!
(Actually, -my- 'dropping' the word 'Solved' here -> search hits

)

taylorkh · 03-20-2017, 08:52 AM

Thanks Jjanel,

I guess the original intent was solved. I need to make one more test to see if I mark this resolved or file a bug. It occurred to me this morning when I was taking my dog on our morning walk - great time for thinking...

Suppose I have a second PC with two NICs which I attach to my 10.42.0 subnet issuing forth from the "Shared..." NIC on the "router" PC. I then set the second NIC on the second PC to "Shared..." If it also gets assigned 10.42.0.1 - Houston we have a problem.

I will update the thread once I have the results (unless I get my network in a DO loop and the whole thing collapses into a black hole

Ken

taylorkh · 03-20-2017, 09:15 AM

As there is no "Partially Solved" "Workaround" nor "Jury-rigged" option in thread tools I will be marking this thread Solved. However, I do need to add a caution. As I posted one reply above and have now tested... If I attempt to daisy chain beyond the 10.42.0 subnet created by the first "Shared with other computers" NIC it WILL NOT WORK. Specifically if a second PC with two NICs is connected to the "Shared.." NIC on the first PC and the second NIC on the second PC is then set to "Shared..." it will be assigned the default 10.42.0.1 address.

Ken