Patricia Bittencourt wrote:
Hi,
I'm dealing with a problem that the worker nodes that are behinda NAT aren't able to reach outside from time to time. (ie: on a given moment I can ping an address name and immediately after I cannot: "ping: unknown host"). The NAT was configurated using the following: *nat -A POSTROUTING -o eth1 -j MASQUERADE COMMIT
Please, any advice here would be appreciated.
The obvious fix is to configure your NAT gateway host as a caching DNS server and make the hosts behind NAT use it's private address instead of something on the other side. However, it should work anyway. Do you have enough traffic that you could be filling your conntrack tables? UDP entries remain for a timeout interval since you can't see a disconnect.
See if the /proc/sys/net/ipv4/netfilter/ip_conntrack_* values are reaonable for your scale.
Patricia Bittencourt wrote:
Thank you Les, John, for the reply. One thing that I noticed is that there are lots of nfs connections in TIME_WAIT. And since I have been facing problems with NFS (ie. taking too much time to cd to a mounting area on client) the problems regarding network appeared.
The TIME_WAIT connections does not free memory, rigth? Do you believe that NFS might be creating a network congestion? Among NFS optimization possibilities is that one in particular that take more effect to avoid performance problems in your oppinion?
TIME_WAIT states happen when you close a TCP connection which shouldn't happen at all on nailed-up mounts. Do you have the automounter set up for short timeouts and something that could be traversing the mount points frequently to stir up traffic and connections? You could switch to UDP to avoid the TCP state handshakes and overhead.
On Thu, 2008-04-24 at 14:27 -0700, Patricia Bittencourt wrote:
Hi,
I'm dealing with a problem that the worker nodes that arebehind a NAT aren't able to reach outside from time to time. (ie: on a given moment I can ping an address name and immediately after I cannot: "ping: unknown host"). The NAT was configurated using the following: *nat -A POSTROUTING -o eth1 -j MASQUERADE COMMIT
Please, any advice here would be appreciated.What's in you /etc/hosts files? You need ip's and names in there for clients on the Lan. You will need a primary and secondary dns addresses in /etc/resolve.conf
Thanks, Patricia
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John -
Les Mikesell -
Patricia Bittencourt