You were redirected to ip.bieringer.net because of
DNS resolution of 'ip.bieringer.de' will be stopped next
Please update your bookmarks
(see also misusage of ip.bieringer.de)

ip.bieringer.net

Carrier-Grade NAT (CGN) Test Page

Home

If you like ipv6calc, Deep Space 6 or ip.bieringer.net you can donate via

PayPal

Liberapay

In case you see only (parts of) one square filling in the IPv4 2D source port distribution and dots are changing colors to yellow/red, yellow/red lines in the histogram and the port reusage > 0%, your system is probably behind a Carrier-Grade NAT device.
Update of graphics every ms and status every ms) Unexpected behavior may occur when used via proxy

This page requires JavaScript enabled!

Switch here to HTTP
Control	Amount of connections to use for test: for test use 8, for analysis 1024/2048 is a good choice
Workflow step
Time [s] Consumed/Left
Protocol	IPv4	IPv6
Status
Info
Address Port
Port Counter
Address Counter
Port Min/Max/Delta Assumed Start/Width Reusage
Histogram each x covers 256 ports each y-dot covers up to 16 hits and above 256 hits as y-dot a line shows an overflow
2D Source Port distribution each dot refers to one source port same port used a 2nd time same port used >= 3 times

How it works using Javascript in local browser:

A sequence of requests are made by browser using 'XMLHttpRequest' to a page returning client IP and port for IPv4 and IPv6
Relation of delta of seen min/max port to amount of ports plus distribution and histogram will show whether Carrier-Grade NAT is probably active or not
Examples:

Using Linux you can simulate the behavior of CGN using e.g. on the host itself by reducing source port range to 256 ports only:

as user "root" execute (don't forget to reset after the test...) for IPv4+IPv6
# record current value sysctl net.ipv4.ip_local_port_range net.ipv4.ip_local_port_range = 32768 60999 # set small range and run test sysctl -w net.ipv4.ip_local_port_range="32768 33023" # reset back to original sysctl -w net.ipv4.ip_local_port_range="32768 60999"
as user "root" execute (don't forget to reset after the test...) for IPv4-only
# add dedicated IPv4 Source-NAT rule restricting outgoing ports iptables -t nat -I POSTROUTING -p tcp -j SNAT --to-source :41984-42239 # run test # remove NAT rule iptables -t nat -D POSTROUTING -p tcp -j SNAT --to-source :41984-42239
as user "root" execute (don't forget to reset after the test...) for IPv6-only
# add dedicated IPv6 Source-NAT rule restricting outgoing ports ip6tables -t nat -I POSTROUTING -p tcp -j SNAT --to-source :41984-42239 # run test # remove NAT rule ip6tables -t nat -D POSTROUTING -p tcp -j SNAT --to-source :41984-42239