170
2.
If the packet has its source IP address found in the FIB table and passes the check, URPF
starts the link layer check.
•
If the
link-check
keyword is not configured, the packet passes the check and is forwarded
normally.
•
If the
link-check
keyword is configured, URPF compares the MAC address of the next hop
in the FIB entry with the source MAC address of the packet. If they are the same, the packet
passes the check; otherwise, the packet is discarded.
The link layer check feature does not support equal-cost paths. If equal-cost paths exist, the link layer check
should be disabled.
Configuring URPF
Follow these steps to configure URPF:
To do...
Use the command…
Remarks
1.
Enter system view
system-view
––
2.
Enter VLAN interface view
interface
interface-type
interface-
number
––
3.
Enable URPF check
ip urpf
strict
[
link-check]
Required
Disabled by default.
•
URPF only checks packets arriving at the interface.
•
When the system works in standard mode, you cannot configure URPF on the VLAN interface that is
bound to a VPN instance configured with no reserved VLAN. For details about the reserved VLAN, see
MPLS L3VPN
in the
MPLS Configuration Guide
.
•
After configuring URPF check on an interface, you can use the
display ip interface
command to view
statistics of packets discarded by URPF (displayed as "Drops") and "Suppressed drops" as mentioned
above.
