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' 0.0.0.0After 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         0.0.0.0         UG        0 0          0 eth1 default         gateway         0.0.0.0         UG        0 0          0 eth0 gateway         0.0.0.0         255.255.255.255 UH        0 0          0 eth0 CentOS-70-64-mi 0.0.0.0         255.255.255.255 UH        0 0          0 eth0 link-local      0.0.0.0         255.255.0.0     U         0 0          0 eth0 188.40.24.199   gateway         255.255.255.255 UGH       0 0          0 eth0 192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 eth1It is CentOS Linux release 7.2.1511 (Core)./etc/sysconfig/network-scripts/ifcfg-eth0:DEVICE=eth0BOOTPROTO=noneONBOOT=yesHWADDR=44:8A:5B:D8:74:B3IPADDR=136.243.34.136NETMASK=255.255.255.255SCOPE=peer 136.243.34.129IPV6INIT=yesIPV6ADDR=2a01:4f8:212:283::2/64IPV6_DEFAULTGW=fe80::1IPV6_DEFAULTDEV=eth0/etc/sysconfig/network-scripts/route-eth0# routing for eth0ADDRESS0=0.0.0.0NETMASK0=0.0.0.0GATEWAY0=136.243.34.129Btw, 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
Network/routing problem with centos
linux;centos;ethernet;route