bridge – IP Ethernet bridge

bind –a #Bb /net

The bridge device bridges packets amongst Ethernet interfaces. The number b in the bind is optional and selects a particular bridge (default 0).

The /net/bridge0 directory contains ctl, cache, log, and stats files, and numbered subdirectories for each physical interface.

Opening the ctl file reserves an interface. The file descriptor returned from the open(2) will point to the control file, ctl, of the newly allocated interface. Reading ctl returns a text string representing the number of the interface. Writing ctl alters aspects of the interface. The possible ctl messages are: bind ether name ownhash path [pvid[#prio][,vlans...]]
Treat the device mounted at path (e.g., /net/ether0) as an Ethernet medium and associate it with this bridge (forward its packets to the other interfaces associated with this bridge). Ownhash is an `owner hash'. The optional [pvid[#prio][,vlans...]] argument is explained in vlan command below.
bind bypass name ownhash path [pvid[#prio][,vlans...]]
This is the same as ether above, but bypasses the physical interface, ignoring all received frames from the interface and diverts all frames transmitted on that interface to the bridge.
bind tunnel name ownhash path path2 [pvid[#prio][,vlans...]]
Treat the device mounted at path as a network tunnel carrying Ethernet packets, the device mounted at path2 as an Ethernet and associate them with this bridge (forward its packets to the other interfaces associated with this bridge). Read packets from the path interface and write them to the path2 interface. Such tunnels have an MTU of 1400 bytes.
vlan pvid[#prio][,vlans...] type name [ownhash]
Change the 802.1Q VLAN configuration of a port identified by type, name and ownhash. The pvid is the "Native" VLAN id associated with untagged packets on a port. Packets with a VLAN id of pvid will be send out untagged on the port. Untagged packets received on the port will be tagged with the pvid. When pvid was not specified in a bind command above, ports default to a pvid of 1. The pvid can be specified as 0 when untagged packets should be ignored on a port. The optional prio argument specifies the default priority to assign to a incoming untagged packet on the port between 0 (lowest, default) and 7 (highest). The vlans... argument specifies comma separated ranges of other VLAN id's that the port is a member of (for trunk ports). Membership means the port is accepting tagged packets with VLAN id's listed here and ignores VLAN id's not listed here. Once accepted, packets are forwarded only to other ports that are members of the same (accepted) VLAN id. Unless pvid is 0, a port is always a member of its own pvid VLAN id, so it does not need to be listed twice.
unbind type name [ownhash]
Disassociate the interface associated with name from this bridge. Type must be ether or tunnel.
Clear the cache of (destination MAC address, VLAN id, port) tuples.
delay delay0 delayn
Set the delay0 and delayn parameters. delay0 is the constant microsecond delay per packet and delayn is the microsecond delay per byte.
set option
Set bridge option. The only known option is tcpmss, which limits the TCP Maximum Segment Size of TCP packets passing through to 1300 bytes.
clear option
Clear bridge option.

Reading stats returns statistics about the bridge.

Reading the log file returns data from the bridge's log and will block at end of file awaiting new data.

Reading the cache file prints the cache of (destination MAC address, VLAN id, port) tuples, one entry per line. The format is: the destination MAC (e.g., Ethernet) address in hex, VLAN id, port number, count of packets from this address, count of packets to this address, expiry time in seconds since the epoch, and e for expired entries or v for valid entries.

In a connection subdirectory, ctl and local don't do anything, but status returns a one–line status summary.

Set up a network bridge between two Ethernets (#l0 and #l1).
bind –a '#B' /net
bind –a '#l1' /net
echo 'bind ether outer 0 /net/ether0' >/net/bridge0/ctl
echo 'bind ether inner 0 /net/ether1' >/net/bridge0/ctl

Set up bridge1 with 3 access ports and a trunk port.
# create bridge1
bind –a '#B1' /net
# nic for trunk carrying only tagged vlans 10,20 and 30
bind –a '#l0' /net
echo 'bind ether trunk 0 /net/ether0 0,10,20,30' >/net/bridge1/ctl
# create virtual nics for access ports
bind –a '#l1:sink ea=001122334401' /net
bind –a '#l2:sink ea=001122334402' /net
bind –a '#l3:sink ea=001122334403' /net
echo 'bind ether port1 0 /net/ether1 10' >/net/bridge1/ctl
echo 'bind ether port2 0 /net/ether2 20' >/net/bridge1/ctl
echo 'bind ether port3 0 /net/ether3 30' >/net/bridge1/ctl

ip(3), ether(3)