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proxy_arp setting on host [message #48425] Wed, 17 October 2012 12:51 Go to next message
Dmitrijs Jerihovs is currently offline  Dmitrijs Jerihovs
Messages: 1
Registered: October 2012
Junior Member
From: *balticom.lv
Hello,

Can someone explain when i need to use proxy_arp enabled on OpenVZ host and
why ?
Re: proxy_arp setting on host [message #48616 is a reply to message #48425] Thu, 25 October 2012 10:55 Go to previous message
Solar Designer is currently offline  Solar Designer
Messages: 5
Registered: August 2011
Junior Member
From: *parallels.com
On Wed, Oct 17, 2012 at 03:51:25PM +0300, Dmitrijs Jerihovs wrote:
> Can someone explain when i need to use proxy_arp enabled on OpenVZ host and
> why ?

Looks like no one has replied, so let me try.

In my experience, proxy_arp may need to be enabled when a container is
assigned an IP address not in a network that the host has a static route
for on one of its interfaces. Configuring such static routes appears to
be a better approach.

For example, if your server is initially on 192.168.100.0/24, and thus
it has this network configured on its eth0, you may proceed to use IPs
in this /24 for containers with no issues and no magic needed. However,
if at a later time you need to use e.g. 192.168.101.101 for a container,
you might have issues unless you either enable proxy_arp or add a static
route on the host's eth0 for a network containing 192.168.101.101 (e.g.,
for 192.168.101.64/26 or whatever network address and netmask is right).

I observed this behavior on RHEL5'ish OpenVZ kernels.

Alexander
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