Ray Van Dolson wrote:
On Thu, May 10, 2007 at 06:34:54PM +0100, Plant, Dean wrote:
Hello List,
Due to a problem with CentOS 5 and one of our firewalls I am having to disable tcp window scaling to stop network connections grinding to a halt. I am also trying to Kickstart CentOS 5 machines through the firewall so need to disable window scaling at install time.
I have added to the kickstart file
%pre echo 0 > /proc/sys/net/ipv4/tcp_window_scaling
But the install still hangs while transferring the stage2.img
Should the above %pre work or do I need to do something else to disable window scaling during the install.
In case anyone's interested CentOS 5 is the first time we have suffered this problem both CentOS 3&4 worked without issue.
Weird issue. Haven't seen anyone else have it (at least on this list).
Can you switch over to your shell console when the hang happens and examine the value of tcp_window_scaling to see if maybe it gets reset somehow? I believe %pre should work....
Weird... Tell me about it, I spent a lot of time head scratching trying to figure out why network connections would just mysteriously hang. Eventually found reference to a problem with tcp_window_scaling and firewalls and after disabling tcp_window_scaling on my test CentOS 5 box, everything started working.
The install does not get far enough for the shell console to be available, it hangs at the transferring stage2.img.
Dean
On Thu, May 10, 2007 at 07:04:51PM +0100, Plant, Dean wrote:
Weird... Tell me about it, I spent a lot of time head scratching trying to figure out why network connections would just mysteriously hang. Eventually found reference to a problem with tcp_window_scaling and firewalls and after disabling tcp_window_scaling on my test CentOS 5 box, everything started working.
The install does not get far enough for the shell console to be available, it hangs at the transferring stage2.img.
Dean
Ah, probably before %pre even has run (?) Well you could rebuild the kernel on the install CD to disable window scaling by default. :) Ok, not a particularly useful option... maybe someone else will have a suggestion.
In HP-UX you can pass kernel parameters at boot-time, I wonder if anything similar could be done? Probably not.
Have you captured a tcpdump of what happens when the "freeze" occurs with an intermediary system? Maybe a setting could be changed on your switch? Although I would doubt the switch would be a factor. Are your packets going through an intermediary router?
I plan to do some network installs of CentOS 5 soon, will be interesting to see if this issue occurs.
Ray
-
Plant, Dean -
Ray Van Dolson