Ericsson EFN324, User Manual, Page: 65 / 176

Glossary
Uplink is defined as an ethernet_port number. A connection must also be
defined from the switching domain to that port before packets may be
forwarded to the uplink.
Note that this measure alone will not always force packets up to the border
node. Intermediate aggregation switches in the Access network might forward
the packet according to the destination address of the packet, before it
reaches the border node. In order to ensure that packets reach the border
node, a gateway for forced forwarding is needed as well.
8.1.2 Define Gateway
The second step is to define a gateway.
Note: a gateway is not needed to enable either IP validation or virtual MAC,
which are described later.
Uplink packets, which are not addressed to the gateway, are discarded.
Downlink packets with other source addresses are also discarded. Note that
the Layer 2 MAC addresses are checked here. The Layer 3 IP addresses are
not checked here.
If these checks are not made, a packet sent from one End­user, directed to a
neighbor connected to the same or a neighboring EFN324, will first be
forwarded through the uplink to an aggregation switch. This switch can
potentially forward the packet directly to the EFN where the intended receiver
is located, rather than towards the border node. That EFN will then
unsuspectingly forward the packet to its destination.
So, in order to ensure that all packets pass the border node, in addition to an
uplink, a gateway should be defined.
Note:
Multicast packets are not subjected to the source address check.
8.1.3 ARP Proxy
The configuration of a gateway automatically activates an ARP proxy function
in the EFN324.
The ARP proxy answers all ARP requests from End­users, with the MAC
address of the gateway. As a result, all packets from End­users have the
gateway as their Layer 2 destination. All other uplink packets are discarded.