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Old 11-06-2012, 10:57 AM   #1
LQ Newbie
Registered: Oct 2012
Posts: 2

Rep: Reputation: Disabled
Unhappy Linux as a router

I am having to learn Linux again. I have a vmware environment with a Linux VM that i am using for routing. There was a setup like this before i got here and i simply cloned the vm as another vm to replicate the router setup for a new subnet i put in place. i have changed the hostname and IP of both interface cards. added the default route and installed and setup dhcp helper. everything works like a champ, i get the dhcp address from my dhcp server. i see the registration on the dhcp server itself. problem is that once the client vm has the dhcp address, it will not ping anything past the new router. i went to the original vm and if i ping from it i can see all of my network and subnets.

the odd thing that i see is that when a client connects to the original router, the dhcp gateway shows the ip of the nic in the router. on the router that is not working, the client dhcp gateway if my firewall on the other side of the router i added.

working router
default route is

client on 10.1 subnet gets dhcp address
it looks like this

non-working router
default route is

client on 12.1 subnet
gets dhcp address
it looks like this

on client on working router all looks okay
on client on non-working router, can't see past linux router

i have compared all the settings i am aware of between the 2 routers and don't see a setting that is different

again haven't worked with Linux and many years and much is changed. i think i am missing something simple, but just not sure at this point. can supply more information if needed.

thanks for any help
Old 11-07-2012, 07:20 AM   #2
Registered: Dec 2006
Distribution: RHEL Debian
Posts: 42

Rep: Reputation: 15
Have you enabled ip forwarding?
Old 11-07-2012, 08:24 AM   #3
LQ Newbie
Registered: Oct 2012
Posts: 2

Original Poster
Rep: Reputation: Disabled
Thanks for the reply,

Part of the problem is solved. I rebooted my firewall last night. Some of the issues seemed to be the firewall not passing to the 12.1 subnet through the static route setup for it. Also found that i had a bad interfaces file on the 12.1 Linux router and that seemed to be causing some of the network issues?, not sure, but when i fixed it and restarted networking, i can now see the other subnets in my network. this was after i had rebooted my firewall and was still having the issue of network unreachable.

the problem now is that when i ping from a client on the 12.1 subnet, the 1.1 subnet replies and all is good. however when i ping my other subnets or try to go to internet, i get request timed out. so it sees the other subnets, but can't connect to them? i tried making the timeout on the ping 5 seconds, but it always replies with request timed out.

the other issue resolved was the bad gateway address. i had the scope option wrong on the dhcp server. once i fixed that the correct 12.1 gateway address showed up on the client in that 12.1 subnet.

i checked the sysctl.conf and the ip forwarding is enabled on boot.

thanks for the help!

Last edited by terryball; 11-07-2012 at 08:27 AM.


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