I have problem with my centos box. After upgrading few packages, after some time network get broken.

What happens is that eth0 is not functional anymore. Only error in log file I have found was this one:

Invalid IP4 netmask 'NETMASK0' ""

After some research I figured out it was problem with route-eth0 config file because network starts, but routes are not added. If I add them manually, then all goes fine.

Without it, routing table is very strange one:

 [root@CentOS-70-64-minimal network-scripts]# route -e
 Kernel IP routing table
 Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
 default         gateway         UG        0 0          0 eth1
 default         gateway         UG        0 0          0 eth0
 gateway UH        0 0          0 eth0
 CentOS-70-64-mi UH        0 0          0 eth0
 link-local     U         0 0          0 eth0   gateway UGH       0 0          0 eth0   U         0 0          0 eth1

It is CentOS Linux release 7.2.1511 (Core).




# routing for eth0

Btw, eth1 is working fine. Also on other server all interfaces are working with same configuration.

Problem may be because it was centos 6 and then updated to centos 7. Maybe some setting left and make problem.

Because site is live, I made temporary solution adding this line to crontab to run every minute:

/etc/sysconfig/network-scripts/ifup-routes eth0
  • pls add centos version to question – sjsam Sep 1 '16 at 21:33
  • 1
    please include the configuration file for eth0 (/etc/sysconfig/network-scripts/ifcfg-eth0) – Rabin Sep 1 '16 at 22:48
  • You can only have a single default route/gateway. It looks like you're trying to set them on both eth1 and eth0. – Eric Renouf Sep 2 '16 at 12:16

If you had configured scope point to point link (because NETMASK= then you wanted to route all traffic via eth0:


I don't understand for what did you configure default route via eth1?

I think you have to change configuration of eth0 interface :


And delete the routing configuration file for eth0 interface. I see that two interfaces are connected to two independent providers. That's why i recommend you to use iproute2. How to configure it you can see at Configuring Multiple Default Routes in Linux


I would suggest you to use nmtui interface to setup IP, route, DNS etc., This will update corresponding configuration files automatically.

nmtui is packaged along with NetworkManager-tui-1.4.0-12.el7.x86_64 rpm.


/etc/sysconfig/network-scripts/route-eth0 is not the correct place to configure the default gateway, that file should be used only for additional static routes. You should have a GATEWAY= line in /etc/sysconfig/network-scripts/ifcfg-eth0 or ifcfg-eth1, not both. Without having some advanced routing having more than one default route is not going to work as your route output shows.

  • It does not help. If I run service network restart eth0 is again without proper gateway. – Živorad Antonijević Sep 2 '16 at 11:09
  • That's probably because you have a default gateway configured on eth1 already. As I said, you can't have two default gateways, not without advanced configuration anyway, which is beyond the scope of this question. – bodgit Sep 2 '16 at 13:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.