3Com 7600 manual Entry obtained by Topology flag Aged by

12-14CHAPTER 12: ATM, LAN EMULATION, AND VIRTUAL LANS

Aging in the LE_ARP As in the transparent bridge FDB, inactive entries in the LE_ARP cache are Cache removed (aged out). Two LEC parameters are employed for this purpose: aging-timeand forward-delay-time. The parameter used depends on the

way the entry was originally obtained and if the topology-flagis set. When the topology flag is set “on” it means that the network is undergoing a change in configuration. The following table shows the conditions under which the appropriate aging parameter is chosen.

Table 12-4Selecting Aging Parameters in the LE_ARP Cache

Entry obtained by	Topology flag Aged by
Address resolution where address	Aging-time
was registered in LES

Address resolution where address was not registered in LES, e.g. proxy LECs

Address learned from received data frames

QSet

QClear

QSet

QClear

Forward-delay-time Aging-time

Forward-delay-time Aging-time

Bridge Frame Forwarding Logic

,

A bridge processes an Ethernet frame received on a bridge port as follows:

1The destination address is looked up in the combined Forwarding Database.

2If the destination address is a local station MAC address the frame is forwarded directly to the bridge port corresponding to the address.

3If the destination address is found on a remote LEC, the frame is converted to the standard LAN Emulation format and sent on to the ATM.

4If the destination address is defined as “self”, this signifies SNMP, CBPDU frames or any other traffic directed to the bridge software.

5If the destination address is unknown, the frame is sent to all local bridge ports. In addition, it is sent to all other members of the ELAN according to the unknown unicast flooding mode (see “Unknown unicast flooding mode” on page 12-15).

6Multicast addresses are handled similarly to unknown addresses; they are flooded.

7Broadcast frames are sent to the bridge software as well as to all other ports on the bridge including the ATM.