Technical data

4. Packages

DEV_MTU_N='1'

DEV_MTU_1='eth0 1496'

4.2.5. BRIDGE - Ethernet Bridging for ﬂi4l

This is a full-ﬂedged ethernet-bridge using spanning tree protocol on demand. For the user

the Computer seems to work as a layer 3 switch on conﬁgured ports.

Further information on bridging can be found here:

• Homepage of the Linux Bridging Project:

http://bridge.sourceforge.net/

• The detailed and authoritative description of the bridging standards:

http://standards.ieee.org/getieee802/download/802.1D-2004.pdf.

(Mainly informations from page 153 on are interesting. Please note that the Linux

bridging code is working according to standards from 1998, allowing only 16 bit Values

for pathcost as an example.)

• Calculation of diﬀerent timing values for the spanning tree protocol:

http://www.dista.de/netstpclc.htm

• See how STP is working by looking at some nice examples:

http://web.archive.org/web/20060114052801/http://www.zyxel.com/support/supportnote/

ves1012/app/stp.htm

OPT_BRIDGE_DEV Default: OPT_BRIDGE_DEV=’no’

’yes’ activates the bridge package, ’no’ deactivates it.

BRIDGE_DEV_BOOTDELAY Default: BRIDGE_DEV_BOOTDELAY=’yes’

This setting is optional and can also be completely omitted.

As a bridge needs at least 2 BRIDGE_DEV_x_FORWARD_DELAY in seconds to become active

this period has to be waited if devices are needed at the startup of the ﬂi4l-router. As

an example consider sending syslog messages or dialing in via DSL. If the entry is set

to ’yes’ 2 BRIDGE_DEV_x_FORWARD_DELAY is waited automatically. If the bridges are

not required at startup-time ’no’ should be set to accelerate the startup process of ﬂi4l

router.

BRIDGE_DEV_N Default: BRIDGE_DEV_N=’1’

The number of independent bridges. Each bridge has to be considered completely iso-

lated. This applies in particular for the setting of BRIDGE_DEV_x_STP. There will be created

one virtual device by the name of ’br nummer ’ per bridge.

BRIDGE_DEV_x_NAME Default: BRIDGE_DEV_x_NAME=”

The symbolic name of the bridge. This name can be used by other packages in order to

use the bridge regardless of its device name.