#### 4.4.2 Host configuration variables

Address = <IP address|hostname> [<port>] [recommended]

  This variable is only required if you want to connect to this host. It must resolve to the external IP address where the host can be reached, not the one that is internal to the VPN. If no port is specified, the default Port is used. Multiple Address variables can be specified, in which case each address will be tried until a working connection has been established.

Cipher = <cipher> (aes-256-cbc)

  The symmetric cipher algorithm used to encrypt UDP packets. Any cipher supported by LibreSSL or OpenSSL is recognized. Furthermore, specifying "none" will turn off packet encryption. It is best to use only those ciphers which support CBC mode.

ClampMSS = <yes|no> (yes)

  This option specifies whether tinc should clamp the maximum segment size (MSS) of TCP packets to the path MTU. This helps in situations where ICMP Fragmentation Needed or Packet too Big messages are dropped by firewalls.

Compression = <level> (0)

  This option sets the level of compression used for UDP packets. Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib), 10 (fast lzo) and 11 (best lzo).

Digest = <digest> (sha256)

  The digest algorithm used to authenticate UDP packets. Any digest supported by LibreSSL or OpenSSL is recognized. Furthermore, specifying "none" will turn off packet authentication.

IndirectData = <yes|no> (no)

  This option specifies whether other tinc daemons besides the one you specified with ConnectTo can make a direct connection to you. This is especially useful if you are behind a firewall and it is impossible to make a connection from the outside to your tinc daemon. Otherwise, it is best to leave this option out or set it to no.

MACLength = <bytes> (4)

  The length of the message authentication code used to authenticate UDP packets. Can be anything from 0 up to the length of the digest produced by the digest algorithm.

PMTU = <mtu> (1514)

  This option controls the initial path MTU to this node.

PMTUDiscovery = <yes|no> (yes)

  When this option is enabled, tinc will try to discover the path MTU to this node. After the path MTU has been discovered, it will be enforced on the VPN.

Port = <port> (655)

  This is the port this tinc daemon listens on. You can use decimal portnumbers or symbolic names (as listed in `/etc/services`).

PublicKey = <key> [obsolete]

  This is the RSA public key for this host.

PublicKeyFile = <path> [obsolete]

  This is the full path name of the RSA public key file that was generated by ‘`tincd --generate-keys`’. It must be a full path, not a relative directory.

  From version 1.0pre4 on tinc will store the public key directly into the host configuration file in PEM format, the above two options then are not necessary. Either the PEM format is used, or exactly one of the above two options must be specified in each host configuration file, if you want to be able to establish a connection with that host.

Subnet = <address[/prefixlength[#weight]]>

  The subnet which this tinc daemon will serve. Tinc tries to look up which other daemon it should send a packet to by searching the appropriate subnet. If the packet matches a subnet, it will be sent to the daemon who has this subnet in his host configuration file. Multiple subnet lines can be specified for each daemon.

  Subnets can either be single MAC, IPv4 or IPv6 addresses, in which case a subnet consisting of only that single address is assumed, or they can be a IPv4 or IPv6 network address with a prefixlength. For example, IPv4 subnets must be in a form like 192.168.1.0/24, where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask. Note that subnets like 192.168.1.1/24 are invalid! Read a networking HOWTO/FAQ/guide if you don’t understand this. IPv6 subnets are notated like fec0:0:0:1::/64. MAC addresses are notated like 0:1a:2b:3c:4d:5e.

  Prefixlength is the number of bits set to 1 in the netmask part; for example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes /22. This conforms to standard CIDR notation as described in RFC1519

  A Subnet can be given a weight to indicate its priority over identical Subnets owned by different nodes. The default weight is 10. Lower values indicate higher priority. Packets will be sent to the node with the highest priority, unless that node is not reachable, in which case the node with the next highest priority will be tried, and so on.

TCPonly = <yes|no> (no) [deprecated]

  If this variable is set to yes, then the packets are tunnelled over a TCP connection instead of a UDP connection. This is especially useful for those who want to run a tinc daemon from behind a masquerading firewall, or if UDP packet routing is disabled somehow. Setting this options also implicitly sets IndirectData.

  Since version 1.0.10, tinc will automatically detect whether communication via UDP is possible or not.