15 Problem Solving
When connection to a desired Web server fails
IPv4 and IPv6 Connection Problems
The possible causes and remedies for problems when using an IPv4 or IPv6 address
are as follows:
Unable to connect using an IPv4 address
Cannot access the proxy
server, firewall, or Web
server as a result of access
The following types of access control are used. Confirm the
configured access control.
Address (port) restriction
User access restriction (including access right levels)
Scheme restriction (cannot use HTTP etc.)
Transfer data size restriction
Method restriction (cannot use POST etc.)
HTTP header restriction (only accepting specified
Time restriction (only available during a specific period of
The setting to use the proxy
server is not configured.
In the environment using the proxy server, you must
configure the machine to use the proxy server to connect to
a desired Web server. Make sure that you configure the
settings to use the proxy server.
The setting to use a proxy
server is configured even
though the environment does
not use a proxy server.
In an environment that does not use a proxy server, such as
when connecting to an intranet, do not make the settings to
use the proxy server.
The proxy server address is
When the settings to use a proxy server are configured, you
cannot connect to a desired Web server only if the IP
address of the proxy server is correct. Set the correct IP
address of the proxy server.
When the proxy server
authentication, you cannot
connect to the server
because the user name or
password is incorrect.
Set the user name and password on the machine that allow
connection to the proxy server.
When 0 (zero) is prepended
to the head of a value for the
IPv4 address (for example:
Do not prepend 0 (zero) to each value of an IPv4 address.