RDOMAIN(4)

NAME
rtable, rdomain - routing tables and routing domains

DESCRIPTION
The traditional kernel routing system had a single table for routes and allowed only non-conflicting IP address assignments. The rtable feature allows multiple lookup tables for routes. The rdomain feature makes it possible to assign the same IP address to more than one interface.

  Routing tables
Each rtable contains routes for outbound network packets. A routing domain can contain more than one rtable. Within a domain, IP addresses used for different interfaces cannot overlap. Multiple routing tables are commonly used for Policy Based Routing.

  Routing domains
Each rdomain is a completely separate address space in the kernel. An IP address (e.g. 10.0.0.1/16) can be assigned in more than one rdomain, but cannot be assigned more than once per rdomain. An interface belongs to one and only one rdomain. The interface's rdomain determines which rdomain an incoming packet will be in. Virtual interfaces do not need to belong to the same rdomain as the parent. Each rdomain contains at least one routing table.

Network traffic within an rdomain stays within the current routing domain. pf(4) is used to move traffic from one rdomain to a different rdomain.

EXAMPLES
Set up em0 and lo4 onto rdomain 4:

    # ifconfig em0 rdomain 4
    # ifconfig lo4 rdomain 4
    # ifconfig lo4 inet 127.0.0.1/8
    # ifconfig em0 192.0.2.100/24

Set a default route and localhost reject route within rdomain 4:

    # route -T4 -qn add -net 127 127.0.0.1 -reject
    # route -T4 -n add default 192.0.2.1

Start an sshd in rdomain 4:

    # route -T4 exec /usr/sbin/sshd

pf.conf snippet to block incoming port 80, and nat-to and move to rtable 0 on interface em1:

    block in on rdomain 4 proto tcp to any port 80
    match out on rdomain 4 to !$internal_net nat-to (em1) rtable 0

SEE ALSO
route(4), pf.conf(5), ifconfig(8), route(8)

HISTORY
OpenBSD support for rdomains first appeared in OpenBSD 4.9 and IPv6 support first appeared in OpenBSD 5.5.