HP 6125G Configuration Manual page 266

Figure 81 URPF work flow
URPF checks the source address validity:
1.
Discards packets with a broadcast source address.
Discards packets with an all-zero source address but a non-broadcast destination address. (A
packet with source address 0.0.0.0 and destination address 255.255.255.255 might be a
DHCP or BOOTP packet, and is not discarded.)
For other packets, proceeds to step 2.
URPF checks whether the source address matches a FIB entry:
2.
If yes, proceeds to step 3.
If not, proceeds to step 6.
URPF checks whether the matching route is a direct route:
3.
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