IBM 8260 Operating Modes for Bridging Ports, ∙ Time-to-Forget, ∙ Time-to-Delete, Normal Mode

To do this, each address in the database has an age assigned to it. When the address is learned, the age is set to zero. At subsequent time intervals this address is incremented. There are two system-wide timers which govern the length of the time the learned entries will be kept in the filtering database:

∙Time-to-Forget

If an address is already in the filtering database and no packets are received from this source by the Multiprotocol Interconnect module within the

time-to-forget interval, then the address is marked as forgotten. Forgotten entries are no longer used for filtering purposes. They remain in the filtering database for historical information, until the time-to-delete period expires.

∙Time-to-Delete

After an address is marked as forgotten, this parameter determines the length of the time the entry may remain in memory without being relearned. If this time expires before any packets are received from the module, the entry is deleted from the filtering database.

Time-to-forget and time-to-delete are system-wide parameters and can be set by the user using the Bridge System Parameters panel.

11.8.5.2 Operating Modes for Bridging Ports

Each port of the Multiprotocol Interconnect module which is configured for bridging (TB or SRT) can operate in one of the following two modes:

1.Normal Mode

In this mode the port can perform the following functions:

∙Can learn new addresses if Source Address Learning is enabled for that port

∙

∙

∙

Can forward/filter frames

Can communicate with network management software

Will participate in spanning tree protocol

2.Security Mode

In this mode the port can perform the following functions:

∙Can learn new addresses if Source Address Learning parameter for that port is enabled

∙

∙

∙

Can forward frame if destination address is permanent or static

Can communicate with network management software

Will participate in spanning tree protocol if STP is enabled

Note that the difference between normal and security mode is that in security mode, only the frames destined to stations with permanent entry will be bridged via the port. You can use the security mode to ensure that the stations attached to a secure port can communicate with specific stations on the other LANs through the Multiprotocol Interconnect module.

The mode for each port can be set independently from the other ports. The setting of the mode is done through the LMS on the Transparent Bridging Port Parameters panel.

Chapter 11. 8260 Multiprotocol Interconnect Module 273