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Static IPs and default route on 1und1 CentOS 5 Servers

I’ve been experiencing some serverdowns at a client who uses 1und1 CentOS 5 Servers. After some investigation I discovered that cronjobs were still running although the server appeared to be down. Checking the syslogs showed me a bunch of failed DHCP requests which remebered me of the fact that 1und1 uses DHCP to configure the server machines. I don’t think this is a good idea so I changed the setup to static IPs.

Since 1und1 puts every server behind a dedicated firewall the setup is not as easy as you think. I’ll document it here because It may be useful for other people and certainly for myself after a couple of months.

Configure a static IP address

Open the file /etc/sysconfig/network-scripts/ifcfg-eth0 and edit it to look like the following:

DEVICE=eth0
BOOTPROTO=none
TYPE=Ethernet
ONBOOT=yes
HWADDR=$YOURMACADDRESS
NETMASK=255.255.255.255
IPADDR=$YOURIP
GATEWAY=10.255.255.1

Save the file.

Configure static routes

This is the tricky part. Configuring a default gateway using the GATEWAY= setting is not enough. You have to setup the routes yourself. To do so create a new file /etc/sysconfig/network-scripts/route-eth0 with the following contents:

10.255.255.1 dev eth0
default via 10.255.255.1 dev eth0

Now you only have to reload the networking configuration via

service network reload

and you are done!

This post helped me a lot with the solution.

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This entry was posted on Wednesday, March 11th, 2009 at 11:10 pm and is filed under Technology. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

2 Responses to “Static IPs and default route on 1und1 CentOS 5 Servers”

  1. bcat Says:
    March 20th, 2009 at 3:15 am

    This was very handy. I have servers at 1und1 also, and an ISP that I do work for on occasion asked if we could do something like this on his client network.

    Thanks!

  2. Sebastian Says:
    March 20th, 2009 at 10:07 am

    Hi,

    I’m glad to hear the post was helpful. Thanks very much for letting me know. This is always very encouraging.

    Best regards,
    Sebastian

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