Packet Forwarding; Aging Time; Filtering Database - D-Link DES-6300 User Manual

Modular L3 Ethernet Switch User's Guide

Packet Forwarding

The Switch learns the network configuration and uses this information to forward packets. This
reduces the traffic congestion on the network, because packets, instead of being transmitted to all
segments, are transmitted to the destination only. Example: if Port 1 receives a packet destined
for a station on Port 2, the Switch transmits that packet through Port 2 only, and transmits
nothing through the other ports.

Aging Time

The Aging Time is a parameter that affects the auto-learn process of the Switch in terms of the
network configuration. Dynamic Entries, which make up the auto-learned-node address, are aged
out of the address table according to the Aging Time that you set.
The Aging Time can be from 10 seconds to 9999 seconds. A very long Aging Time can result
with the out-of-date Dynamic Entries that may cause incorrect packet filtering/forwarding
decisions.
On the other hand, if the Aging Time is too short, many entries may be aged out soon, resulting
in a high percentage of received packets whose source addresses cannot be found in the address
table, in which case the Switch will broadcast the packet to all ports, negating many of the
benefits of having a switch.

Filtering Database

A switch uses a filtering database to segment the network and control communications between
segments. It also filters packets off the network for intrusion control (MAC Address filtering).
For port filtering, each port on the switch is a unique collision domain and the switch filters
(discards) packets whose destination lies on the same port as where it originated. This keeps
local packets from disrupting communications on other parts of the network.
For intrusion control, whenever a switch encounters a packet originating from or destined to a
MAC address defined by the user, the switch will discard the packet.
Filtering includes:
Dynamic filtering – Automatic learning and aging of MAC addresses and their location on the
network. Filtering occurs to keep local traffic confined to its segment.
MAC address filtering – The manual entry of specific MAC addresses to be filtered from the
network.
Filtering done by the Spanning Tree Protocol – Able to filter packets based on topology,
making sure that signal loops don't occur.
Filtering done for VLAN integrity – Packets from a member of a VLAN (VLAN 2, for
example) destined for a device on another VLAN (VLAN 3) will be filtered.
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