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Ethan Brouwer
Asked: 2015-08-21 12:11:07 +0800 CST

Server abandons set static ip and returns to dhcp given address

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I have a few virtualized (ubuntu 14.04 LTS) servers under KVM that I'm trying to move to an ip block other than the one reserved for servers under dhcp (the 10.10.2.0/24 block). I change the ip and then run this command:

sudo ifdown -a && sudo ifup -a

And the whole setup on the new ip works for a little while. Then, after a few minutes, it all of a sudden switches back to wrong ip, even though my /etc/network/interfaces file is unchanged. Here it is:

# Interface lo
auto lo
iface lo inet loopback

# Interface eth0
auto eth0
iface eth0 inet static
    address 10.10.28.4
    netmask 255.255.0.0
    network 10.10.0.0
    broadcast 10.10.255.255
    dns-nameservers 10.10.85.2 10.10.85.71 8.8.8.8
    dns-search lan
    gateway 10.10.85.2

But my ifconfig is changed. I can repeat this over and over, but every time it switches ips (after I do nothing on the server for a bit) and my ssh connection just closes. Any thoughts? What other information might you need to help? Thanks in advance! This is super frustrating!

Edit: Just in case it does help, here's the two ifconfig outputs. After I set the static ip:

eth0      Link encap:Ethernet  HWaddr 52:54:00:51:b8:76  
          inet addr:10.10.28.4  Bcast:10.10.255.255  Mask:255.255.0.0
          inet6 addr: fe80::5054:ff:fe51:b876/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:102914 errors:0 dropped:4 overruns:0 frame:0
          TX packets:31863 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:148249682 (148.2 MB)  TX bytes:4566351 (4.5 MB)

And after it switches back:

eth0      Link encap:Ethernet  HWaddr 52:54:00:51:b8:76  
          inet addr:10.10.2.98  Bcast:10.10.255.255  Mask:255.255.0.0
          inet6 addr: fe80::5054:ff:fe51:b876/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:96960 errors:0 dropped:4 overruns:0 frame:0
          TX packets:29960 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:147748205 (147.7 MB)  TX bytes:4315514 (4.3 MB)
ubuntu

1 Answers

  1. Best Answer

    It sounds like network-manager is reverting the interface back to dhcp because it's not aware of the config change.

    Rather than doing ifup/ifdown restart the network-manager service:

    sudo service network-manager restart

    If network-manager isn't installed check to see if dhclient is still running. If it is stop it and try restarting the interface again.

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