brconfig

Configure network bridge parameters

Syntax:

brconfig -a

or:

brconfig  bridge [command [args ...]]

Runs on:

Neutrino

Options:

-a

Display the status of all bridge devices present on the system. This flag is mutually exclusive with all other subcommands.

All other operations require that a bridge be specified. If a bridge is specified with no subcommands, the status of that bridge is displayed. The following subcommands are available:

up

Start forwarding packets on the bridge.

down

Stop forwarding packets on the bridge.

add interface

Add the interface named by interface as a member of the bridge. The interface is put into promiscuous mode so that it can receive every packet sent on the network.

delete interface

Remove the interface named by interface from the bridge. Promiscuous mode is disabled on the interface when it's removed from the bridge.

maxaddr size

Set the size of the bridge address cache to size. The default is 100 entries.

timeout seconds

Set the timeout of address cache entries to the given number of seconds. If seconds is zero, then address cache entries don't expire. The default is 1200 seconds.

deladdr address

Delete address from the address cache.

flush

Delete all dynamically-learned addresses from the address cache.

flushall

Delete all addresses, including static addresses, from the address cache.

discover interface

Mark an interface as a “discovering” interface. When the bridge has no address cache entry (either dynamic or static) for the destination address of a packet, the bridge forwards the packet to all member interfaces marked as “discovering.” This is the default for all interfaces added to a bridge.

-discover interface

Clear the “discovering” attribute on a member interface. For packets without the “discovering” attribute, the only packets forwarded on the interface are broadcast or multicast packets and packets for which the destination address is known to be on the interface's segment.

learn interface

Mark an interface as a “learning” interface. When a packet arrives on such an interface, the source address of the packet is entered into the address cache as being a destination address on the interface's segment. This is the default for all interfaces added to a bridge.

-learn interface

Clear the “learning” attribute on a member interface.

stp interface

Enable the IEEE 802.1D Spanning Tree Protocol (STP) on the interface. Spanning Tree is used to detect and remove loops in a network topology.

-stp interface

Disable the Spanning Tree Protocol on the interface. This is the default for all interfaces added to a bridge.

maxage seconds

Set the time that a Spanning Tree Protocol configuration is valid. The default is 20 seconds, the minimum 1 second, and the maximum 255 seconds.

fwddelay seconds

Set the time that must pass before an interface begins forwarding packets when Spanning Tree is enabled. The default is 15 seconds, the minimum 1 second, and the maximum 255 seconds.

hellotime seconds

Set the time between broadcasting of Spanning Tree protocol configuration messages. The default is 2 seconds, the minimum 1 second, and the maximum 255 seconds.

priority value

Set the bridge priority for Spanning Tree. The default is 32768. Allowed numerical values range from 0 (highest priority) to 65535 (lowest priority).

ifpriority interface value

Set the Spanning Tree priority of the interface to value. The default is 128, the minimum 0, and the maximum 255.

ifpathcost interface value

Set the Spanning Tree path cost of the interface to value. The default is 55, the minimum 0, and the maximum 65535.

Description:

The brconfig utility is used to configure network bridge parameters and retrieve network bridge parameters and status from io-pkt.

A network bridge creates a logical link between two or more IEEE 802 networks that use the same (or “similar enough”) framing format. For example, it's possible to bridge Ethernet and 802.11 networks together, but it isn't possible to bridge Ethernet and Token Ring networks together.

To create a bridge interface, use the ifconfig command's create subcommand. Perform all other bridge configuration using the brconfig utility.

Examples:

The following code, when placed in the file /etc/ifconfig.bridge0, creates a bridge called bridge0, adds the interfaces ray0 and fxp0 to the bridge, and then enables packet forwarding. You could use such a configuration to implement a simple 802.11-to-Ethernet bridge (assuming the 802.11 interface is in ad hoc mode).

create
!brconfig $int add ray0 add fxp0 up

Consider a system with two 4-port Ethernet boards. The following code, when placed in the file /etc/ifconfig.bridge0 causes a bridge consisting of all eight ports to be created with Spanning Tree enabled:

create
!brconfig $int \
add tlp0 stp tlp0 \
add tlp1 stp tlp1 \
add tlp2 stp tlp2 \
add tlp3 stp tlp3 \
add tlp4 stp tlp4 \
add tlp5 stp tlp5 \
add tlp6 stp tlp6 \
add tlp7 stp tlp7 \
up

See also:

ifconfig, pf