carta
nos-tun(8)

nos-tun8

Implement ``nos'' or ``ka9q'' style ip over ip tunnel

Usage

nos-tun -t tunnel -s source -d destination -p protocol_number [source] target

Overview

The nos-tun utility is used to establish an nos style tunnel, (also known as ka9q or IP-IP tunnel) using a tun(4) kernel interface.

Tunnel is the name of the tunnel device /dev/tun0 for example.

Source and destination are the addresses used on the tunnel device. If you configure the tunnel against a cisco router, use a netmask of “255.255.255.252” on the cisco. This is because the tunnel is a point-to-point interface in the FreeBSD end, a concept cisco does not really implement.

Protocol number sets tunnel mode. Original KA9Q NOS uses 94 but many people use 4 on the worldwide backbone of ampr.org.

Target is the address of the remote tunnel device, this must match the source address set on the remote end.

Examples

This end, a FreeBSD box on address 192.168.59.34:

nos-tun -t /dev/tun0 -s 192.168.61.1 -d 192.168.61.2 192.168.56.45

Remote cisco on address 192.168.56.45:

interface tunnel 0
ip address 192.168.61.2 255.255.255.252
tunnel mode nos
tunnel destination 192.168.59.34
tunnel source 192.168.56.45

History

  • FreeBSD 16.0-CURRENT (2026-10-27) to FreeBSD 13.3-RELEASE: the text shown here
  • FreeBSD 13.2-RELEASE to FreeBSD 13.0-RELEASE
  • FreeBSD 12.4-RELEASE
  • FreeBSD 12.3-RELEASE
  • FreeBSD 12.2-RELEASE
  • FreeBSD 12.1-RELEASE
  • FreeBSD 12.0-RELEASE
  • FreeBSD 11.4-RELEASE
  • FreeBSD 11.3-RELEASE
  • FreeBSD 11.2-RELEASE
  • FreeBSD 11.1-RELEASE
  • FreeBSD 11.0-RELEASE
  • FreeBSD 10.4-RELEASE
  • FreeBSD 10.3-RELEASE
  • FreeBSD 10.2-RELEASE
  • FreeBSD 10.1-RELEASE
  • FreeBSD 10.0-RELEASE
  • FreeBSD 9.3-RELEASE
  • FreeBSD 9.2-RELEASE
  • FreeBSD 9.1-RELEASE
  • FreeBSD 9.0-RELEASE
  • FreeBSD 8.4-RELEASE
  • FreeBSD 8.3-RELEASE
  • FreeBSD 8.2-RELEASE
  • FreeBSD 8.1-RELEASE
  • FreeBSD 8.0-RELEASE
  • FreeBSD 7.4-RELEASE
  • FreeBSD 7.3-RELEASE
  • FreeBSD 7.2-RELEASE
  • FreeBSD 7.1-RELEASE
  • FreeBSD 7.0-RELEASE
  • FreeBSD 6.4-RELEASE
  • FreeBSD 6.3-RELEASE to FreeBSD 6.0-RELEASE
  • FreeBSD 5.5-RELEASE to FreeBSD 5.3-RELEASE
  • FreeBSD 5.2.1-RELEASE to FreeBSD 5.0-RELEASE
  • FreeBSD 4.11-RELEASE to FreeBSD 4.8-RELEASE
  • FreeBSD 4.7-RELEASE to FreeBSD 4.5-RELEASE
  • FreeBSD 4.4-RELEASE
  • FreeBSD 4.3-RELEASE
  • FreeBSD 4.2-RELEASE to FreeBSD 4.0-RELEASE
  • FreeBSD 3.5.1-RELEASE to FreeBSD 3.3-RELEASE
  • FreeBSD 3.2-RELEASE to FreeBSD 3.0-RELEASE

History

The nos-tun utility appeared in FreeBSD 3.0.

Authors

Nickolay N. Dudorov ⟨[email protected]⟩ wrote the program, Poul-Henning Kamp ⟨[email protected]⟩ wrote the man-page. Isao SEKI ⟨[email protected]⟩ added a new flag, IP protocol number.

Bugs

We do not allow for setting our source address for multihomed machines.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.