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I have Cloudmin setup on a CentOS 64 bit server and I have several virtual machines running on it using Xen.

When I try to change the 'Maximum network speed' in Cloudmin from Unlimited to anything (to throttle the VMs internet speed), the VM reports 'Ping failed' - and I am then unable to connect via SSH to it.

If I then change the Network speed back to Unlimited, it works fine. What could be the problem? I originally posted this on the Cloudmin forums a few days ago but have had no response so I thought I would post it here.

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please edit your post to include a link to the other forum where you asked this so that anybody considering answering or following the other discussion track can do so. This is always good etiquette when cross-posting. –  Caleb Apr 18 '11 at 16:31
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@Caleb I have now added the link. –  Joel Kennedy Apr 18 '11 at 17:06

1 Answer 1

I suspect this is the fault of incomplete programming in Cloudmin. They probably took a shortcut in the whole scenario and only enabled traffic shaping for TCP (and maybe UDP). My guess is that without traffic shaping enabled, there are just some normal NAT rules in place. With traffic shaping, everything is put into buckets, perhaps derived from tc or a similar system, and ICMP traffic is not taking into consideration at all. You can confirm this by using nmap or another tool to scan the network addresses with probes in several protocols and see if all ICMP traffic really is killed when enabling rate limiting, or if something peculiar is happening to ping.

I am not a cloudmin guy, so that is all speculation. Anybody else out there that can test this?

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