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Chapter 1 Introduction Installation and Operation Manual

1-16 Functional Description Egate-100 Ver. 4.0

Frames are forwarded, dropped, or flooded at this stage for the following reason:

• Forwarded – A frame will be forwarded according to its DA, to the bridge port

where its DA was learned

• Dropped – Local filtering: if the port for that DA entry in the MAC table is the

port on which the frame was received, the frame will be dropped

• Flooded –

 If there is no information regarding the DA in the MAC table then the

frame is flooded to all ports

 Frames with multicast or broadcast address are flooded to all ports.

Egress Process

In this bridge mode, the frames are transmitted unchanged: No tags are added or

removed.

VLAN Ethertype

By default, the system uses Ethertype 8100 to identify and manipulate VLAN

frames (including stacking and other actions).

It is possible to configure Egate-100 to use another Ethertype to identify and

manipulate VLAN frames. Thus, Egate-100 can support a proprietary VLAN

Ethertype (9100) or new standards (S-TAG per 802.1ad using 88A8).

The Egate-100 VLAN Ethertype configuration is in effect for any VLAN

identification and operation. Thus, only frames with the configured Ethertype are

identified as VLAN-tagged frames, and all stacking operations are done using the

configured Ethertype.

Split Horizon

The Egate-100 split horizon functionality overrides the VLAN-aware bridge

forwarding rules, and imposes a logical forwarding restriction on the bridge

standard behavior to support certain application requirements.

The basic VLAN-aware bridge forwarding rules determine that bridge ports

sharing the same VLAN act as the same Ethernet segment for this VLAN. This

means that unicast connectivity between the ports is possible and broadcasts,

multicasts, and unknown unicasts are flooded to all ports sharing the same VLAN.

There are applications where remote sites sharing the same VLAN must disable

the local switching performed at Egate-100 between the remote sites. An

example of such an application is Internet Access/DSLAM Aggregation.

There are three options for Split Horizon:

• Enabling local switching

• Disabling switching between the PDH ports for all LANs

• Enabling Split Horizon for specific VLANs. This means that for example

Internet access VLANs may use Split Horizon while other VLANs used for VPNs

between remotes still use the connectivity between the bridge ports at the

Egate-100 level.

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RAD Data comm 100 Dokumentacja Strona 48