Technical data

4. Packages

Very unusual problems can appear especially using EBTables without perfectly knowing the

diverse operational modes of layer 2 and 3. Some ﬁltering rules of the packet ﬁlter will work

completely diﬀerent with EBTables support enabled.

4.2.1. Broadcast Relay - Forwarding of IP Broadcasts

Using a Broadcast Relay, IP broadcasts can surpass interface boundaries. This is necessary

for applications which determine network devices using broadcasts (eg QNAP Finder). Broad-

casts are normally not passed across network boundaries by the router. This problem can be

circumvented by using a broadcast relay.

Within a Broadcast Relay broadcasts are always forwarded to all connected interfaces. This

means that setting up a second Broadcast Relay with interfaces swapped is not necessary. In

addition, multiple broadcast relays including the same interface are not allowed.

OPT_BCRELAY Broadcast Forwarding

Default: OPT_BCRELAY=’no’

Setting ’yes’ here activates the Broadcast Relay package. Specifying ’no’ deactivates

the Broadcast Relay package completely.

BCRELAY_N Default: BCRELAY_N=’0’

The number of Broadcast Relays to conﬁgure.

BCRELAY_x_IF_N Default: BCRELAY_x_IF_N=’1’

Number of interfaces assigned to this broadcast relay.

BCRELAY_x_IF_x Default: BCRELAY_x_IF_x=” Name of the interface assigned to this broad-

cast relay.

For illustration an example follows where the computer with the application (eg QNAP

Finder) is located in the internal network (connected to eth0) and the NAS is in a diﬀerent

network (connected to eth1).

OPT_BCRELAY='yes'

BCRELAY_N='1'

BCRELAY_1_IF_N='2'

BCRELAY_1_IF_1='eth0'

BCRELAY_1_IF_2='eth1'

4.2.2. Bonding - Combining Several Network Interface Cards In One Link

Bonding refers to joining at least two network interface cards into one link. The cards even

may be of diﬀerent type (ie 3Com and Intel) or speed (ie 10 Mbit/s or 100 Mbit/s). You can

either connect linux computers directly or connect to a network switch using bonding. In this

way a 200 Mbit/s full duplex connection from a ﬂil4-router to a switch can be used without

much eﬀort. Everyone interested in using bonding should have read the documentation in the

kernel directory (bonding.txt). The names of the bonding settings largely correspond to the

names used there.