How FDB Entries Get Added

The MAC entries that are added to the FDB are learned in the following ways:

Source MAC entries are learned from ingress packets on all platforms. This is Layer 2 learning.
On all switches, MAC entries can be learned at the hardware level.
Virtual MAC addresses embedded in the payload of IP ARP packets can be learned when this feature is enabled.
Static entries can be entered using the command line interface (CLI).
Dynamic entries can be modified using the CLI.
Static entries for switch interfaces are added by the system upon switch boot-up.

The ability to learn MAC addresses can be enabled or disabled on a port-by-port basis. You can also limit the number of addresses that can be learned, or you can lock down the current entries and prevent additional MAC address learning.

BlackDiamond 8000 and BlackDiamond X8 series modules and Summit switches support different FDB table sizes.

On a BlackDiamond 8800 and BlackDiamond X8 series switch with a variety of modules or on a SummitStack with different Summit switch models, the FDB tables on some modules or switches can be filled before the tables on other modules or switches. In this situation, when a lower-capacity FDB table cannot accept FDB entries, a message appears that is similar to the following:

 HAL.FDB.Warning> MSM-A: FDB for vlanID1 mac 00:00:03:05:15:04 was not added to slot 3 - table full.

Note

For information on increasing the FDB table size on BlackDiamond 8900 and BlackDiamond X8 xl-series modules, and Summit X480 switches, see Increasing the FDB Table Size. For information on FDB tables sizes, see the ExtremeXOS Release Notes.

Published March 2020prev | next

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