HP 5920 Series - Page 365

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Figure 121 uRPF work flow
1. uRPF checks source address validity:
{ 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 cannot be discarded.)
{ Proceeds to step 2 for other packets.
Checks the received packet
Broadcast source
address?
All-zero source address?
Matching FIB entry
found?
Broadcast destination
address?
Default route found?
Loose uRPF?
Allows the packet to pass
Discards the packet
Yes
Yes
Yes
Yes
No
Yes
Yes
No
No
Receiving
interface matches the output
interface of the default
route？
No
No
NoNo
Loose uRPF?
Yes
No
No
Yes
Yes
Receiving
interface matches the
output interface of the
matching FIB entry？
Matching route is a direct
route?
No
Source IP address
matches an ARP entry?
Yes
No
Yes