411
[SwitchB-FortyGigE1/1/1] quit
[SwitchB] interface fortygige 1/1/2
[SwitchB-FortyGigE1/1/2] port link-mode route
[SwitchB-FortyGigE1/1/2] ip address 10.10.1.1 24
# Enable DHCP relay agent on FortyGigE 1/1/2.
[SwitchB-FortyGigE1/1/2] dhcp select relay
# Add the DHCP server 10.1.1.1 to DHCP server group 1.
[SwitchB-FortyGigE1/1/2] dhcp relay server-address 10.1.1.1
# Enable authorized ARP.
[SwitchB-FortyGigE1/1/2] arp authorized enable
[SwitchB-FortyGigE1/1/2] quit
# Enable recording of relay entries on the relay agent.
[SwitchB] dhcp relay client-information record
3.
Configure Switch C:
<SwitchC> system-view
[SwitchC] ip route-static 10.1.1.0 24 10.10.1.1
[SwitchC] interface fortygige 1/1/2
[SwitchC-FortyGigE1/1/2] port link-mode route
[SwitchC-FortyGigE1/1/2] ip address dhcp-alloc
[SwitchC-FortyGigE1/1/2] quit
Verifying the configuration
# Display authorized ARP information on Switch B.
[SwitchB] display arp all
Type: S-Static D-Dynamic O-Openflow M-Multiport I-Invalid
IP Address MAC Address VLAN Interface Aging Type
10.10.1.2 0012-3f86-e94c N/A FGE1/1/2 20 D
The output shows that Switch A assigned the IP address 10.10.1.2 to Switch C.
Switch C must use the IP address and MAC address in the authorized ARP entry to communicate
with Switch B. Otherwise, the communication fails. Thus the user validity is ensured.
Configuring ARP detection
ARP detection enables access devices to block ARP packets from unauthorized clients to prevent
user spoofing and gateway spoofing attacks. ARP detection does not check ARP packets received
from ARP trusted ports.
ARP detection provides the following features:
•
User validity check.
•
ARP packet validity check.
•
ARP restricted forwarding.
•
ARP detection logging.
If both ARP packet validity check and user validity check are enabled, the former one applies first,
and then the latter applies.
