2factor VPN - Network connection problems after connecting via 2factor VPN

By default, 2factor VPN users are assigned a single, static IP address. Users will experience network connectivity problems if they log into the 2factor VPN service from multiple computers or, in rare circumstances, if they connect multiple times from the same computer.

This document relates to the 2factor (OCIS) VPN service which is provided by the Office of Cybersecurity for users who need VPN access for interacting with highly sensitive data. It should not be confused with the more general WiscVPN service, which is available to all UW-Madison students, faculty, and staff with a valid NetID.


The 2factor VPN service is configured such that each user only has one available IP address. In order for network traffic to route correctly, each computer needs to have a unique IP. If you attempt to connect to 2factor VPN from multiple computers using the same certificate, additional computers may receive an error such as "Illegal address class" or "Host or network is 0" or "Other error". The reason for this error is that your assigned IP is already in use on another computer.

This issue may sometimes also occur when a previous connection attempt gets "stuck" without properly disconnecting.


If you are connected to 2factor VPN from multiple computers, disconnect from 2factor on all computers and then reconnect using only one computer. If you are connected from only one computer and encounter this problem, the issue may be with a stuck connection. If you wait, the connection may automatically expire after 15 minutes. Otherwise, contact the DoIT Help Desk and we will work with the 2factor admins to resolve the issue.

Keywords:virtual private network office of campus information security secure wireless sensitive data protecting protection 2factor VPN IP conflicts network issue connectivity connection problem timeout   Doc ID:14823
Owner:Gary F.Group:Office of Campus Information Security
Created:2010-08-09 19:00 CDTUpdated:2015-10-02 10:29 CDT
Sites:DoIT Help Desk, Office of Campus Information Security
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