HP 3600 v2 Series Configuration Manual page 411

Figure 126 URPF work flow
Yes
Does
No
the source IP
address match an
ARP entry?
No
1. URPF checks the source address validity:
Discards packets with a limited source broadcast 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.)
Check the source
address of the
received packet
A broadcast
source address?
No
An all-zone
source address?
No
Does the FIB
entry match the
source address?
Yes
Loose URPF?
No
Yes
Is the matching
route a direct
route?
No
Does
the receiving
interface match the
output interface of the
matching FIB entry?
No
398
Yes
Yes
A broadcast
Yes
destination
addres?
Is there a default
No
route?
Yes
Yes
Loose URPF?
No
Does
the output interface of
Yes
the default route match
the receiving
interface?
Yes
Check passed
No
Discard
No
No