[CentOS] Fwd: Different behavior of net.ipv4.ip_local_port_range between RHEL-5 and RHEL-6

Thu Nov 8 08:53:54 UTC 2012
Santi Saez <santi at woop.es>

Forwarding just in case anyone is familiar with this on CentOS, thanks!



Just found that net.ipv4.ip_local_port_range has different behavior
between RHEL releases: until v6 although you have multiple source IPs
you can only use a fixed number of local ports, seems that
"ip_local_port_range" is a global configuration or limitation. On RHEL-6
kernel (testing with 2.6.32-279) you can bind() to N local ports per
source IP, it's a per-IP limit: total ports = ip_local_port_range x
source IP.

The problem is that on RHEL-5 and 4 you can only make
ip_local_port_range outgoing connections and you can't use different
source IPs trick to increase this limitation. I have been testing and
vanilla 2.6.32 kernel and other Linux distributions like Debian doesn't
support this. What has been changed/patched on RHEL-6 to allow this?

Santi Saez