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Page 806 / 998 Scroll up to view Page 801 - 805
Bridge
Basic bridge configuration
iMG/RG Software Reference Manual (ADSL Port)
8-36
GenericTrace
= DSP
debug
= disable
MaxRSMemory
= 32
Profile
= MAIN
DetectNoise
= Disable
PortSpeed
= 2405
resetDefaults
= false
8.4
Bridge
The transparent bridge on the Allied Telesis Media Gateway main application software provides MAC level
bridging for Ethernet-like networks. The transparent bridge may be configured to interconnect different type of
interfaces in order to forward packets that arrive from a specific physical media to another different physical
media.
The transparent bridge plays a fundamental rule in the Allied Telesis Media Gateway architecture because it is
used not only for pure bridging functionality but it’s also used when routing is performed between ip interfaces
attached to Ethernet ports to ipinterfaces attached to ADSL port (only when RFC1483 encapsulation type is
used).
8.4.1
Basic bridge configuration
The following picture reports the basic bridge configuration that is always present in any Allied Telesis Media
Gateway system configuration, note that group ADSL C devices have a 6 ethernet switch ports on board but
the basic principles operation are the same.
Page 807 / 998
Basic bridge configuration
Bridge
8-37
iMG/RG Software Reference Manual (ADSL Port)
FIGURE 8-2
Basic software bridge configuration
The bridge software and the overall system architecture has been designed in order to have frames forwarded
by the bridge always being tagged frames. All the bridge interfaces must therefore be able to manage tagged
frames.
The bridge software has two interfaces named
defaulti
and
qinterface
respectively.
The
defaulti
interface receives always tagged frames from the switch chipset that is configured to support multi-
ple vlan on the Ethernet ports and manage tagged/untagged frames. The
defaulti
interface forwards tagged
frames either to the bridge
qinterface
or to other configured bridge interfaces based on the destination MAC
address (see below).
The Allied Telesis Media Gateway is always configured with one ip interface ip0 attached (connection
b
) on an
Ethernet transport named
t1
.
The transport
t1
add a tag header with VID = 1 to all the outgoing packets routed or generated by ip0 interface.
These packets arriving on the bridge interface
qinterface
will be forwarded to the other bridge interfaces
depending on the destination MAC address registered in the bridge database: if the bridge has previously regis-
tered the destination MAC address as belong to a specific interface, the packet will be forwarded only to this
interface, otherwise the packet is forwarded to all the existing interfaces.
qinterface
Bridge Software
L2 switch
bunbridge
dynamic
VID 1 (tagged)
a
VID 1 (untagged)
b
t1
ip0
defaulti
VID 1 (tagged)
c
VID 1 (tagged)
default
cpu
lan1
lan2
lan3
lan4
ethernet0
Page 808 / 998
Bridge
Multiple VLAN support
iMG/RG Software Reference Manual (ADSL Port)
8-38
In the opposite direction, packets arriving from
qinterface
(connection
a
) are filtered by the
bunbridge
module
and only tagged packets having VID = 1 are sent to ip0 interface.
8.4.2
Multiple VLAN support
Bunbridge port is an intermediate layer between the bridge
qinterface
and the ethernet transport
t1
. This inter-
mediate layer is used to separate tagged frames received from
qinterface
based on the VID value:
•
It remove the tag header from tagged framed with VID=1 and then forward them to ip0 interface;
•
it forward any other tagged frames with VID
≠
1 to an additional intermediate port, named
ethernet1
(see
example below).
Ethernet1
port looks like an additional system port that receives tagged frames (from the bridge) and forward
them to Ethernet transports modules depending on the VID value. Each Ethernet transport will then remove
the tag header from the frames and will forward such untagged frames to the IP interface attached to it.
Once frames are arrived to the IP layer, routing functions as well as any other functionality that operates at
layer 3/4 can be performed.
FIGURE 8-3
Example of system architecture to support multiple vlan management
vlan 7
vlan 1
qinterface
Bridge Software
bunbridge
VID 4 (tagged)
VID 7 (tagged)
VID 1 (tagged)
VID 4 (tagged)
VID 7 (tagged)
VID 1 (tagged)
VID 4 (tagged)
VID 7 (tagged)
VID 1 (tagged)
VID 4 (tagged)
VID 7 (tagged)
VID 1 (tagged)
t1
ip0
bunbridge
VID 4 (tagged)
vlan_4
ip_4
bunbridge
VID 7 (tagged)
VID 1 (untagged)
VID 4 (untagged)
VID 7 (untagged)
vlan_7
ip_7
defaulti
default
lan1
lan2
lan3
lan4
ethernet0
ethernet1
vlan 4
cpu
vlan 7
vlan 4
vlan 1
Page 809 / 998
Bridge command reference
Bridge
8-39
iMG/RG Software Reference Manual (ADSL Port)
8.4.3
Bridge command reference
8.4.3.1 Bridge CLI commands
This chapter describes the
Bridge
commands provided by the CLI:
8.4.3.1.1 BRIDGE ADD INTERFACE
Syntax
BRIDGE ADD INTERFACE <name>
Description
This command adds a named interface to the bridge.
Options
The following table gives the range of values for each option that can be specified with
this command and a default value (if applicable).
Example
--> bridge add interface pvc_1_32_if
TABLE 8-3
Bridge commands
Functions
Fiber
A
Fiber
B
Fiber
C
Fiber
D
Fiber
E
Modular
ADSL
A
ADSL
B
ADSL
C
BRIDGE ADD INTERFACE
X
X
X
BRIDGE ADD VLANINTERFACE
X
X
BRIDGE ATTACH
X
X
X
BRIDGE CLEAR INTERFACES
X
X
X
BRIDGE DELETE INTERFACE
X
X
X
BRIDGE DETACH
X
X
X
BRIDGE LIST INTERFACES
X
X
X
BRIDGE LIST VLANS
X
X
BRIDGE SET FILTERAGE
X
X
X
BRIDGE SET INTERFACE FILTERTYPE
X
X
X
BRIDGE SET INTERFACE PORTFILTER
BRIDGE SHOW
X
X
X
BRIDGE SHOW INTERFACE
X
X
X
Option
Description
Default Value
name
An arbitrary name that identifies the interface. It can be
made up of one or more letters or a combination of letters
and digits, but it cannot start with a digit.
N/A
Page 810 / 998
Bridge
Bridge command reference
iMG/RG Software Reference Manual (ADSL Port)
8-40
See also
BRIDGE ATTACH
BRIDGE LIST INTERFACES
BRIDGE LIST VLAN
8.4.3.1.2 BRIDGE ADD VLANINTERFACE
Description
BRIDGE ADD VLANINTERFACE
{<name>|number} {tagged|untagged} <interfacename>
This command adds an interface in the egress interface list of the named VLAN. The
egress interface list for a VLAN is the union of tagged interfaces and the untagged inter-
faces. For the default VLAN, all the bridge interfaces, are automatically configured as its
untagged egress interfaces. The user need not explicitly add untagged interfaces for the
DefaultVlan.
Options
The following table gives the range of values for each option that can be specified with
this command and a default value (if applicable).
Example
--> bridge add vlainterface vlan666 tagged pvc_0_35_if
See also
BRIDGE LIST VLAN
BRIDGE LIST INTERFACES
8.4.3.1.3 BRIDGE ATTACH
Syntax
BRIDGE ATTACH {<name>|<number>} <transport>
Description
This command attaches an existing transport to an existing bridge interface to allow data
to be bridged via the transport.
Only one transport can be attached to an interface. If you use this command when there
is already a transport attached to the interface; the new transport replaces the previous
one.
This command implicitly enables the transport being attached.
Option
Description
Default Value
name
A name that identifies an existing VLAN. To display the list of
statically configured VLANs, use
bridge list static vlans.
N/A
number
A number that identifies an existing VLAN.
tagged
To add a port in the tagged port list of the named VLAN.
untagged
To add a port in the untagged port list of the named VLAN.

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