SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The ALE table contains 1024 entries. Each table entry represents a free entry, an address, a VLAN, an address/VLAN pair, or an OUI address. Software should ensure that there are not double address entries in the table. The double entry used would be indeterminate. Reserved table bits must be written with zeroes.
Source Address learning occurs for packets with a unicast, multicast or broadcast destination address and a unicast or multicast (including broadcast) source address. Multicast source addresses have the group bit (bit 40) cleared before ALE processing begins, changing the multicast source address to a unicast source address. A multicast address of all ones is the broadcast address which may be added to the table. A learned unicast source address is added to the table with the following control bits:
Bit(s) | Value |
---|---|
unicast_type | 11 |
Block | 0 |
Secure | 0 |
If a received packet has a source address that is equal to the destination address then the following occurs:
Table Entry Type
00 - Free Entry
01 - Address Entry : unicast or multicast determined by destination address bit 40.
10 - VLAN entry
11 - VLAN Address Entry : unicast or multicast determined by address bit 40.