VEB(4) FreeBSD Kernel Interfaces Manual VEB(4)
NAME
veb, vport - Virtual Ethernet Bridge network device
SYNOPSIS
pseudo-device veb
DESCRIPTION
The veb pseudo-device supports the creation of a single layer 2 Ethernet
network between multiple ports. Ethernet interfaces are added to the veb
bridge to be used as ports. Unlike bridge(4), veb takes over the
operation of the interfaces that are added as ports. They are then
independent of the host network stack: the individual Ethernet ports no
longer function as independent devices and cannot be configured with
inet(4) or inet6(4) addresses or other layer-3 features themselves.
The Ethernet network managed by veb can be connected to the network stack
as a whole by creating a vport interface and attaching it as a port to
the bridge. From the perspective of the host network stack, a vport
interface acts as a normal interface connected to an Ethernet network and
can be configured with addresses.
veb is a learning bridge that maintains a table of Ethernet addresses and
the port that each address is reachable with. The bridge learns about
the reachability of Ethernet addresses by reading the source address on
packets received by ports, and then entering the address and port into
the table dynamically. Static address entries may also be configured in
the table, disabling dynamic learning for that address. Ethernet address
learning can be disabled on individual ports.
When forwarding a packet, the address table is searched for the
destination Ethernet address and the packet is sent to the associated
port in the table entry. If no entry is found in the table, or the
packet is addressed to a multicast or broadcast address, the packet is
flooded to all other ports on the bridge. Flooding of packets to unknown
unicast addresses can be disabled on individual ports.
veb provides multiple mechanisms for filtering packets traversing the
bridge. By default it filters IEEE 802.1Q VLAN and SVLAN packets, but
can be configured to forward them by setting the link0 flag. veb can
filter Ethernet packets entering or leaving ports using bridge rules.
Ports can be configured as members of protected domains to restrict
communication between them.
pf(4) can be used to filter IP packets as they enter or leave the bridge.
By default this filtering is disabled, but can be enabled by setting the
link1 flag. The exception to this policy is on vport interfaces, where
pf(4) runs as packets enter and leave the network stack regardless of the
value of the link1 flag. A consequence of this behaviour is that packets
traversing vport interfaces appear to travel in the opposite direction to
packets travelling over other ports.
veb supports the addition of span ports to the bridge. Span ports
transmit a copy of every packet received by the bridge, allowing for
passive monitoring of traffic on a separate host.
SEE ALSO
ipsec(4), options(4), pf(4), hostname.if(5), ifconfig(8), netstart(8)
HISTORY
The veb driver first appeared in OpenBSD 6.9.
AUTHORS
David Gwynne <
[email protected]>
FreeBSD 14.1-RELEASE-p8 October 28, 2021 FreeBSD 14.1-RELEASE-p8