432
{
If yes, uRPF proceeds to step 3.
{
If no, uRPF proceeds to step 6.
3.
uRPF checks whether the check mode is loose:
{
If yes, uRPF proceeds to step 8.
{
If no, uRPF checks whether the matching route is a direct route:
−
If yes, uRPF proceeds to step 5.
−
If no, uRPF proceeds to step 4.
4.
uRPF checks whether the receiving interface matches the output interface of the matching FIB
entry:
{
If yes, uRPF proceeds to step 8.
{
If no, uRPF proceeds to step 9.
5.
uRPF checks whether the source IP address matches an ARP entry:
{
If yes, uRPF proceeds to step 8.
{
If no, uRPF proceeds to step 9.
6.
uRPF checks whether the FIB table has a default route:
{
If yes, uRPF proceeds to step 7.
{
If no, uRPF proceeds to step 9.
7.
uRPF checks whether the check mode is loose:
{
If yes, uRPF proceeds to step 8.
{
If no, uRPF checks whether the output interface of the default route matches the receiving
interface of the packet:
−
If yes, uRPF proceeds to step 8.
−
If no, uRPF proceeds to step 9.
8.
The packet passes the check and is forwarded.
9.
The packet is discarded.
NOTE:
uRPF does not check multicast packets.
