Technical data

4. Packages

BRIDGE_DEV_x_DEV_x_PATHCOST Default: BRIDGE_DEV_x_DEV_x_PATHCOST=’100’

This setting is optional and can also be completely omitted.

Only valid if BRIDGE_DEV_x_STP=’yes’ is set!

Indirectly speciﬁes the bandwidth for this connection. The lower the value the higher is

the bandwidth and therefore the connection gets a higher priority.

The calculation base proposed is 1000000 kbit/s which leads to the traﬃc costs listed in

table 4.1. Please note to use the actual usable bandwidth in the formula when calculating.

As a result this leads to signiﬁcantly lower values than you would expect, especially on

wireless lan.

Note: The current IEEE standard from 2004 uses 32 bit numbers for bandwidth calcu-

lation which is not supported on Linux yet.

Bandwidth Setting of BRIDGE_DEV_x_DEV_x_PATHCOST

64 kbit/s 15625

128 kbit/s 7812

256 kbit/s 3906

10 Mbit/s 100

11 Mbit/s 190

54 Mbit/s 33

100 Mbit/s 10

1 Gbit/s 1

Table 4.1.: Values for BRIDGE_DEV_x_DEV_x_PATHCOST as a function of bandwidth

4.2.6. Notes

A bridge will forward any type of Ethernet data - thus e.g. a regular DSL modem can be used

over WLAN as if it had a WLAN interface. No packets that pass the bridge will be examined

for any undesirable activities (ie the ﬂi4l packet ﬁlter is not active!). Use only after careful

consideration of security risks (ie as a WLAN access point). There is also the possibility to

activate EBTables support however.

4.2.7. EBTables - EBTables for ﬂi4l

As of Version 2.1.9 ﬂi4l has rudimental EBTables support. By setting OPT_EBTABLES=’yes’

EBTables support will get activated.

This means that all ebtables kernel modules get loaded and the ebtables program on the

ﬂi4l-routers will get available. In contrast to the much simpliﬁed netﬁlter conﬁguration through

the diﬀerent ﬁlter lists of ﬂi4l it then is necessary to write an ebtables script of your own. This

means you have to write the complete ebtables script yourself.

For background informations about EBTables support please read the EBTables documen-

tation at http://ebtables.sourceforge.net.

There is the possibility of issuing ebtables commands on the router before and after setting

up the netﬁlter (PF_INPUT_x, PF_FORWARD_x etc). To do so, create the ﬁles ebtables.pre und