weirdness with slow ssh connections (IPv6 related?)

[Eric Shubert]

Steven A. DuChene wrote:
> I am working on a project with 50 - 70 servers in the AT&T data center
> on University. They have either RHEL5U3 or CentOS5U3 on the systems.
> I have DNS configured with the normal bind 9 packages that come with
> CentOS5U3. My problem is when using ssh to get between the systems
> if i use the short name for a system it takes a long time to get to
> a shell prompt on the remote system. If I use the fully qualified
> domain name or the IP address of I use a "-4" with the short name
> I get to a shell prompt immediately. So to illustrate:
> 
> root at adm #  ssh new75
> 
> takes a LONG time to get shell prompt.
> 
> Any of the following get me a shell prompt almost immediately:
> 
> root at adm #  ssh -4 new75
> 
> root at adm #  ssh new75.wholedomain.here
> 
> root at adm #  ssh 10.4.5.6   (IP address of new75 system)
> 
> Since the "-4" option seems to have a positive effect I have gone
> to each system and made sure the IPv6 kernel modules are not loaded
> and the network file in /etc/sysconfig/ has the following line in
> it:
> 
> NETWORKING_IPV6=no
> 
> but that made little or no difference to the problem. The lines
> I added to the /etc/modprobe.conf file look like this:
> 
> alias net-pf-10 off
> alias ipv6 off
> 
> I believe it some strange interaction problem between IPv6 and DNS
> but I do not have a clear plan on what to try next.
> 
> Any suggestions?
> --
> Steven DuChene
> 
> 

http://forums.cpanel.net/f5/rh-5-4-update-bind-named-network-unreachable-resolving-ipv6-129889.html
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-- 
-Eric 'shubes'