Your company here — click to reach over 10,000 unique daily visitors

openconnect - Man Page

Multi-protocol VPN client, for Cisco AnyConnect VPNs and others

Examples (TL;DR)



The program openconnect connects to VPN servers which use standard TLS/SSL, DTLS, and ESP protocols for data transport.

It was originally written to support Cisco "AnyConnect" VPN servers, and has since been extended with experimental support for Juniper Network Connect (--protocol=nc), Junos/Ivanti Pulse VPN servers (--protocol=pulse), PAN GlobalProtect VPN servers (--protocol=gp), F5 Big-IP VPN servers (--protocol=f5), Fortinet Fortigate VPN servers (--protocol=fortinet), and Array Networks SSL VPN servers (--protocol=array).

The connection happens in two phases. First there is a simple HTTPS connection over which the user authenticates somehow - by using a certificate, or password or SecurID, etc.  Having authenticated, the user is rewarded with an authentication cookie which can be used to make the real VPN connection.

The second phase uses that cookie to connect to a tunnel via HTTPS, and data packets can be passed over the resulting connection. When possible, a UDP tunnel is also configured: AnyConnect uses DTLS, while Juniper and GlobalProtect use UDP-encapsulated ESP. The UDP tunnel may be disabled with --no-dtls, but is preferred when correctly supported by the server and network for performance reasons. (TCP performs poorly and unreliably over TCP-based tunnels; see http://sites.inka.de/~W1011/devel/tcp-tcp.html.)



Read further options from CONFIGFILE before continuing to process options from the command line. The file should contain long-format options as would be accepted on the command line, but without the two leading -- dashes. Empty lines, or lines where the first non-space character is a # character, are ignored.

Any option except the config option may be specified in the file.


Continue in background after startup


Save the pid to PIDFILE when backgrounding

-c,--certificate=CERT [,--mca-certificate=CERT]

Use SSL client certificate CERT which may be either a file name or, if OpenConnect has been built with an appropriate version of GnuTLS, a PKCS#11 URL.

The --mca-certificate option sets the secondary certificate for multi-certificate authentication (according to Cisco's terminology, the SSL client certificate is called the "machine" certificate, and the second certificate is called the "user" certificate).


Give a warning when SSL client certificate has DAYS left before expiry

-k,--sslkey=KEY [,--mca-key=KEY]

Use SSL private key KEY which may be either a file name or, if OpenConnect has been built with an appropriate version of GnuTLS, a PKCS#11 URL.

The --mca-key option sets the private key for the secondary certificate (see --mca-certificate).


Use authentication cookie COOKIE.


Read cookie from standard input.


Enable all compression, including stateful modes. By default, only stateless compression algorithms are enabled.


Disable all compression.


Set compression mode, where MODE is one of stateless, none, or all.

By default, only stateless compression algorithms which do not maintain state from one packet to the next (and which can be used on UDP transports) are enabled. By setting the mode to all stateful algorithms (currently only zlib deflate) can be enabled. Or all compression can be disabled by setting the mode to none.


Use INTERVAL as Dead Peer Detection interval (in seconds). This will cause the client to use DPD at the specified interval even if the server hasn't requested it, or at a different interval from the one requested by the server.

DPD mechanisms vary by protocol and by transport (TLS or DTLS/ESP), but are all functionally similar: they enable either the VPN client or the VPN server to transmit a signal to the peer, requesting an immediate reply which can be used to confirm that the link between the two peers is still working.


Set the URL path of the initial HTTPS connection to the server.

With some protocols, this path may function as a login group or realm, hence the naming of this option. For example, the following invocations of OpenConnect are equivalent:

openconnect --usergroup=loginPath vpn.server.com
openconnect https://vpn.server.com/loginPath

Provide authentication form input, where FORM and OPTION are the identifiers from the form and the specific input field, and VALUE is the string to be filled in automatically. For example, the standard username field (also handled by the --user option) could also be provided with this option thus: --form-entry main:username=joebloggs.

If VALUE is not specified, this option will cause a hidden form field to be treated as a standard text-input field.

This option should not be used to enter passwords. --passwd-on-stdin should be used for that purpose. Not only will this option expose the password value via the OpenConnect process's command line, but unlike --passwd-on-stdin this option will not recognize the case of an incorrect password, and stop trying to re-enter it repeatedly.


Display help text


Use only the specified methods for HTTP authentication to a server.  By default, only Negotiate, NTLM and Digest authentication are enabled. Basic authentication is also supported but because it is insecure it must be explicitly enabled. The argument is a comma-separated list of methods to be enabled. Note that the order does not matter: OpenConnect will use Negotiate, NTLM, Digest and Basic authentication in that order, if each is enabled, regardless of the order specified in the METHODS string.


Set BROWSER as the executable used by OpenConnect to handle the authentication process with gateways that support the single-sign-on-external-browser authentication method.


Use IFNAME for tunnel interface


After tunnel is brought up, use syslog for further progress messages


Prepend a timestamp to each progress message


Copy TOS / TCLASS of payload packet into DTLS and ESP packets. This is not set by default because it may leak information about the payload (for example, by differentiating voice/video traffic).


Drop privileges after connecting, to become user USER


Drop privileges during execution of trojan binary or script (CSD, TNCC, or HIP).


Run SCRIPT instead of the trojan binary or script.


Use INTERVAL as interval (in seconds) for repeat execution of Trojan binary or script, overriding default and/or server-set interval.


Request MTU from server as the MTU of the tunnel.


Indicate MTU as the path MTU between client and server on the unencrypted network. Newer servers will automatically calculate the MTU to be used on the tunnel from this value.

-p,--key-password=PASS [,--mca-key-password=PASS]

Provide passphrase for certificate file, or SRK (System Root Key) PIN for TPM

--mca-key-password provides the passphrase for the secondary certificate (see --mca-certificate).


Use HTTP or SOCKS proxy for connection. A username and password can be provided in the given URL, and will be used for authentication. If authentication is required but no credentials are given, GSSAPI and automatic NTLM authentication using Samba's ntlm_auth helper tool may be attempted.


Use only the specified methods for HTTP authentication to a proxy.  By default, only Negotiate, NTLM and Digest authentication are enabled. Basic authentication is also supported but because it is insecure it must be explicitly enabled. The argument is a comma-separated list of methods to be enabled. Note that the order does not matter: OpenConnect will use Negotiate, NTLM, Digest and Basic authentication in that order, if each is enabled, regardless of the order specified in the METHODS string.


Disable use of proxy


Use libproxy to configure proxy automatically (when built with libproxy support)


Passphrase for certificate file is automatically generated from the fsid of the file system on which it is stored. The fsid is obtained from the statvfs(2) or statfs(2) system call, depending on the operating system. On a Linux or similar system with GNU coreutils, the fsid used by this option should be equal to the output of the command:

stat --file-system --printf=%i\\n $CERTIFICATE

It is not the same as the 128-bit UUID of the file system.


Less output


Set packet queue limit to LEN packets. The default is 32. A high value may allow better overall bandwidth but at a cost of latency. If you run Voice over IP or other interactive traffic over the VPN, you don't want those packets to be queued behind thousands of other large packets which are part of a bulk transfer.

This option sets the maximum inbound and outbound packet queue sizes in OpenConnect itself, which control how many packets will be sent and received in a single batch, as well as affecting other buffering such as the socket send buffer (SO_SNDBUF) for network connections and the OS tunnel device.

Ultimately, the right size for a queue is "just enough packets that it never quite gets empty before more are pushed to it". Any higher than that is simply introducing bufferbloat and additional latency with no benefit. With the default of 32, we are able to saturate a single Gigabit Ethernet from modest hardware, which is more than enough for most VPN users.

If OpenConnect is built with vhost-net support, it will only be used if the queue length is set to 16 or more. This is because vhost-net introduces a small amount of additional latency, but improves total bandwidth quite considerably for those operating at high traffic rates. Thus it makes sense to use it when the user has indicated a preference for bandwidth over latency, by increasing the queue size.


Invoke SCRIPT to configure the network after connection. Without this, routing and name service are unlikely to work correctly. The script is expected to be compatible with the vpnc-script which is shipped with the "vpnc" VPN client. See https://www.infradead.org/openconnect/vpnc-script.html for more information. This version of OpenConnect is configured to use /etc/vpnc/vpnc-script by default.

On Windows, a relative directory for the default script will be handled as starting from the directory that the openconnect executable is running from, rather than the current directory. The script will be invoked with the command-based script host cscript.exe.


Pass traffic to 'script' program over a UNIX socket, instead of to a kernel tun/tap device. This allows the VPN IP traffic to be handled entirely in userspace, for example by a program which uses lwIP to provide SOCKS access into the VPN.


Define the VPN server as a simple HOST or as an URL containing the HOST and optionally the PORT number and the PATH; with some protocols, the path may function as a login group or realm, and it may equivalently be specified with --usergroup.

As an alternative, define the VPN server as non-option command line argument.


Set login username to NAME


Report version number


More output (may be specified multiple times for additional output)


XML config file


Select GROUP from authentication dropdown or list entry.

Many VPNs require a selection from a dropdown or list during the authentication process. This selection may be known as authgroup (on Cisco VPNs), realm (Juniper, Pulse, Fortinet), domain (F5), and gateway (GlobalProtect). This option attempts to automatically fill the appropriate protocol-specific field with the desired value.


Authenticate to the VPN, output the information needed to make the connection in a form which can be used to set shell environment variables, and then exit.

When invoked with this option, OpenConnect will not actually create the VPN connection or configure a tunnel interface, but if successful will print something like the following to stdout:


Thus, you can invoke openconnect as a non-privileged user (with access to the user's PKCS#11 tokens, etc.) for authentication, and then invoke openconnect separately to make the actual connection as root:

eval `openconnect --authenticate https://vpnserver.example.com`;
[ -n ["$COOKIE"] ] && echo ["$COOKIE"] |
  sudo openconnect --cookie-on-stdin $CONNECT_URL --servercert $FINGERPRINT --resolve $RESOLVE

Earlier versions of OpenConnect produced only the HOST variable (containing the numeric server address), and not the CONNECT_URL or RESOLVE variables. Subsequently, we discovered that servers behind proxies may not respond correctly unless the correct DNS name is present in the connection phase, and we added support for VPN protocols where the server URL's path component may be significant in the connection phase, prompting the addition of CONNECT_URL and RESOLVE, and the recommendation to use them as described above. If you are not certain that you are invoking a newer version of OpenConnect which outputs these variables, use the following command-line (compatible with most Bourne shell derivatives) which will work with either a newer or older version:

sudo openconnect --cookie-on-stdin ${CONNECT_URL:-$HOST} --servercert $FINGERPRINT ${RESOLVE:+--resolve=$RESOLVE}

Fetch and print cookie only; don't connect (this is essentially a subset of --authenticate).


Print cookie to stdout before connecting (see --authenticate for the meaning of this cookie)


Additional CA file for server verification. By default, this simply causes OpenConnect to trust additional root CA certificate(s) in addition to those trusted by the system. Use --no-system-trust to prevent OpenConnect from trusting the system default certificate authorities.


Do not trust the system default certificate authorities. If this option is given, only certificate authorities given with the --cafile option, if any, will be trusted automatically.


Do not advertise IPv6 capability to server


Set OpenSSL ciphers to support for DTLS


Set OpenSSL ciphers for Cisco's DTLS v1.2


Use PORT as the local port for DTLS and UDP datagrams


Enable verbose output of all HTTP requests and the bodies of all responses received from the server.


Enforces Perfect Forward Secrecy (PFS). That ensures that if the server's long-term key is compromised, any session keys established before the compromise will be unaffected. If this option is provided and the server does not support PFS in the TLS channel the connection will fail.

PFS is available in Cisco ASA releases 9.1(2) and higher; a suitable cipher suite may need to be manually enabled by the administrator using the ssl encryption setting.


Disable DTLS and ESP


Version of the Cisco ASA software has a bug where it will forget the client's SSL certificate when HTTP connections are being re-used for multiple requests. So far, this has only been seen on the initial connection, where the server gives an HTTP/1.0 redirect response with an explicit Connection: Keep-Alive directive. OpenConnect as of v2.22 has an unconditional workaround for this, which is never to obey that directive after an HTTP/1.0 response.

However, Cisco's support team has failed to give any competent response to the bug report and we don't know under what other circumstances their bug might manifest itself. So this option exists to disable ALL re-use of HTTP sessions and cause a new connection to be made for each request. If your server seems not to be recognizing your certificate, try this option. If it makes a difference, please report this information to the openconnect-devel@lists.infradead.org mailing list.


Never attempt password (or SecurID) authentication.


Prevent OpenConnect from advertising to the server that it supports any kind of authentication mode that requires an external browser.

Some servers will force the client to use such an authentication mode if the client advertises it, but fallback to a more "scriptable" authentication mode if the client doesn't appear to support it.


Do not attempt to post an XML authentication/configuration request to the server; use the old style GET method which was used by older clients and servers instead.

This option is a temporary safety net, to work around potential compatibility issues with the code which falls back to the old method automatically. It causes OpenConnect to behave more like older versions (4.08 and below) did. If you find that you need to use this option, then you have found a bug in OpenConnect. Please see https://www.infradead.org/openconnect/mail.html and report this to the developers.


The ancient, broken 3DES and RC4 ciphers are insecure; we explicitly disable them by default. However, some still-in-use VPN servers can't do any better.

This option enables use of these insecure ciphers, as well as the use of SHA1 for server certificate validation.


Do not expect user input; exit if it is required.


Read password from standard input


Select VPN protocol PROTO to be used for the connection. Supported protocols are anyconnect for Cisco AnyConnect (the default), nc for experimental support for Juniper Network Connect (also supported by most Junos/Ivanti Pulse servers), pulse for experimental support for Junos/Ivanti Pulse, gp for experimental support for PAN GlobalProtect, f5 for experimental support for F5 Big-IP, fortinet for experimental support for Fortinet Fortigate, and array for experimental support for Array Networks SSL VPN.

See https://www.infradead.org/openconnect/protocols.html for details on features and deficiencies of the individual protocols.

OpenConnect does not yet support all of the authentication options used by Pulse, nor does it support Host Checker/TNCC with Pulse. If your Junos/Ivanti Pulse VPN is not yet supported with --protocol=pulse, then --protocol=nc may be a useful fallback option.


Enable one-time password generation using the MODE algorithm. --token-mode=rsa will call libstoken to generate an RSA SecurID tokencode, --token-mode=totp will generate an RFC 6238 time-based password, and --token-mode=hotp will generate an RFC 4226 HMAC-based password. Yubikey tokens which generate OATH codes in hardware are supported with --token-mode=yubioath. --token-mode=oidc will use the provided OpenIDConnect token as an RFC 6750 bearer token.

--token-secret={ SECRET[,COUNTER] | @FILENAME }

The secret to use when generating one-time passwords/verification codes. Base 32-encoded TOTP/HOTP secrets can be used by specifying "base32:" at the beginning of the secret, and for HOTP secrets the token counter can be specified following a comma.

RSA SecurID secrets can be specified as an Android/iPhone URI or a raw numeric CTF string (with or without dashes).

For Yubikey OATH the token secret specifies the name of the credential to be used. If not provided, the first OATH credential found on the device will be used.

For OIDC the secret is the bearer token to be used.

FILENAME, if specified, can contain any of the above strings.  Or, it can contain a SecurID XML (SDTID) seed.

If this option is omitted, and --token-mode is "rsa", libstoken will try to use the software token seed saved in ~/.stokenrc by the "stoken import" command.


After disconnection or Dead Peer Detection, keep trying to reconnect for SECONDS. The default is 300 seconds, which means that openconnect can recover a VPN connection after a temporary network outage lasting up to 300 seconds.


Automatically resolve the hostname HOST to IP instead of using the normal resolver to look it up.


When creating new TLS connections, always present the hostname HOST as the SNI (Server Name Indication) in place of the correct hostname, which will still be sent in the HTTP 'Host:' header, and expect the peer's certificate to match the SNI rather than the correct hostname. This may be useful for Domain Fronting, by which some filtered or censored Internet connections can be bypassed.

Note that sending different values for the SNI and 'Host:' header violates HTTP standards and is prevented by many cloud hosting providers.


Accept server's SSL certificate only if it matches the provided fingerprint. This option implies --no-system-trust, and may be specified multiple times in order to accept multiple possible fingerprints.

The allowed fingerprint types are SHA1, SHA256, and PIN-SHA256. They are distinguished by the 'sha1:', 'sha256:' and 'pin-sha256:' prefixes to the encoded hash. The first two are custom identifiers providing hex encoding of the peer's public key, while 'pin-sha256:' is the RFC7469 key PIN, which utilizes base64 encoding. To ease certain testing use-cases, a partial match of the hash will also be accepted, if it is at least 4 characters past the prefix.


Use STRING as 'User-Agent:' field value in HTTP header.

Some VPN servers may require specific values matching those sent by proprietary VPN clients in order to successfully authenticate or connect. For example, when connecting to a Cisco VPN server, --useragent 'AnyConnect Windows 4.10.06079' or --useragent 'Cisco AnyConnect VPN Agent for Windows 2.2.0133', or when connecting to a Pulse server, --useragent 'Pulse-Secure/'.


Use STRING as the software version reported to the head end. (e.g. --version-string '2.2.0133')


Use STRING as 'X-CSTP-Hostname:' field value in HTTP header. For example --local-hostname 'mypc', will advertise the value 'mypc' as the suggested hostname to point to the provided IP address.


OS type to report to gateway.  Recognized values are: linux, linux-64, win, mac-intel, android, apple-ios. Reporting a different OS type may affect the dynamic access policy (DAP) applied to the VPN session.  If the gateway requires CSD, it will also cause the corresponding CSD trojan binary to be downloaded, so you may need to use --csd-wrapper if this code is not executable on the local machine.


In the data phase of the connection, the following signals are handled:


performs a clean shutdown by logging the session off, disconnecting from the gateway, and running the vpnc-script to restore the network configuration.


disconnects from the gateway and runs the vpnc-script, but does not log the session off; this allows for reconnection later using --cookie.


writes progress message with detailed connection information and statistics.


forces an immediate disconnection and reconnection; this can be used to quickly recover from LAN IP address changes.


See https://www.infradead.org/openconnect/contribute.html for various features that we wish OpenConnect had, and https://www.infradead.org/openconnect/protocols.html for information on the quirks and limitations of the individual VPN protocols.

See Also



David Woodhouse <dwmw2@infradead.org>

Referenced By

ocproxy(1), ocserv(8), vpnns(1).