3Com 7600 manual Spanning Tree, Protocol, Address of a bridge port, called Self

11-8CHAPTER 11: ETHERNET LANS AND BRIDGES IN THE 7600 CARD

Static Addresses The network manager may want to restrict a particular station to

	communicate only through specific input and output bridge ports in
	order to keep its traffic confined to certain portions of the network
	topology. Or, he may want to maintain a station that transmits so
	infrequently that it would be aged-out by the aging mechanism. For
	these cases the learning method is not suitable. Instead, the FDB provides
	for address entries called static addresses. These are entered or removed
	manually by the operator (and are therefore also called Management
	addresses) or they can be supplied with the device. The Read-onlyaddress
	is a special type of static address which is supplied with the device for
	internal use and cannot be altered. An example of a Read-only address is
	the address of a bridge port, called “Self”.
Defining	In the 7600 Card, static addresses with various degrees of permanency
permanency of	can be defined as follows:
static addresses

Allowed ports for static addresses

QPermanent - Entries that remain in the FDB when the device is reset

QDelete-on-Reset - Entries that are deleted when the device is reset

QDelete-on-Timeout - Static entry that is deleted after the aging time

Input and output bridge ports assigned (allowed) to a static address are entered or removed by the operator or are predefined. Static addresses can be addresses of individual destination stations but they are more frequently multicast addresses - addresses which include a group of destination stations. A packet with a multicast address normally needs to be transmitted on more than one bridge port in order to reach all the destination stations. Consequently, multiple output bridge ports are often allowed to a single static address. For data display, multiple allowed output ports are coded into a single binary number. Normally, one input (or receiving) port is allowed to a static address, but it is also possible to designate all ports as allowed receiving ports.

Blocking ports for static addresses

Instead of specifying the allowed input and output bridge ports for a static address, it is sometimes more convenient to specify those input and output bridge ports which are not allowed for that address (blocked ports). Then all ports other than the blocked ports can receive and transmit for that address.

Spanning Tree	When designing a bridged-LAN environment is it desirable to build
Protocol	redundant bridge links between LANs: in case one link fails, another can
	serve as a backup. However, when a LAN is attached to two or more