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Chapter 39 The Number Limitation Function of
MAC in Port Configuration
39.1 Introduction to the Number
Limitation Function of MAC in Port
MAC address list is used to identify the mapping relationship between the destination MAC
addresses and the ports of switch. There are two kinds of MAC addresses in the list: static
MAC address and dynamic MAC address. The static MAC address is set by users, having the
highest priority (will not be overwritten by dynamic MAC address), and will always be effective;
dynamic MAC address is learnt by the switch through transmitting data frames, and will only
be effective in a specific time range. When the switch receives a data framed waiting to be
transmitted, it will study the source MAC address of the data frame, build a mapping
relationship with the receiving port, and then look up the MAC address list for the destination
MAC address. If any matching list entry is found, the switch will transmit the data frame via the
corresponding port, or, the switch will broadcast the data frame over the VLAN it belongs to. If
the dynamically learnt MAC address matches no transmitted data in a long time, the switch will
delete it from the MAC address list.
Usually the switch supports both the static configuration and dynamic study of MAC address,
which means each port can have more than one static set MAC addresses and dynamically
learnt MAC addresses, and thus can implement the transmission of data traffic between port
and known MAC addresses. When a MAC address becomes out of date, it will be dealt with
broadcast. No number limitation is put on MAC address of the ports of our current switches;
every port can have several MAC addressed either by configuration or study, until the
hardware list entries are exhausted. To avoid too many MAC addresses of a port, we should
limit the number of MAC addresses a port can have.
To summer up, it is very meaningful to develop the number limitation function of MAC of port.
Switch can control the number of MAC address of ports through configuration commands.
Limiting the number of dynamic MAC of ports:
1. Limiting the number of dynamic MAC. If the number of dynamically learnt MAC address by
the switch is already larger than or equal with the max number of dynamic MAC address, then
shutdown the MAC study function on this port, otherwise, the port can continue its study.
Summary of Contents for QSW-2800 series
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