H3C Technologies H3C S12500-X Series Switches - Manual (Page 237)

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[SwitchB-Ten-GigabitEthernet1/0/1] quit
[SwitchB] interface ten-gigabitethernet 1/0/2
[SwitchB-Ten-GigabitEthernet1/0/2] ip address 10.10.1.1 24
# Enable DHCP relay agent on Ten-GigabitEthernet 1/0/2.
[SwitchB-Ten-GigabitEthernet1/0/2] dhcp select relay
# Add the DHCP server 10.1.1.1 to DHCP server group 1.
[SwitchB-Ten-GigabitEthernet1/0/2] dhcp relay server-address 10.1.1.1
# Enable authorized ARP.
[SwitchB-Ten-GigabitEthernet1/0/2] arp authorized enable
[SwitchB-Ten-GigabitEthernet1/0/2] quit
# Enable recording of relay entries on the relay agent.
[SwitchB] dhcp relay client-information record
3. Configure Switch C:
system-view
[SwitchC] ip route-static 10.1.1.0 24 10.10.1.1
[SwitchC] interface ten-gigabitethernet 1/0/2
[SwitchC-Ten-GigabitEthernet1/0/2] ip address dhcp-alloc
[SwitchC-Ten-GigabitEthernet1/0/2] quit
536B
Verifying the configuration
After Switch C obtains an IP address from Switch A, display the 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 XGE1/0/2 20 D
The output shows that Switch A assigned an 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.
138B
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 user validity check, ARP packet validity check, and ARP restricted forwarding
functions.
If both ARP packet validity check and user validity check are enabled, the former one applies first, and
then the latter applies.
310B
Configuring user validity check
Upon receiving an ARP packet from an ARP untrusted interface, the device compares the sender IP and
MAC addresses against the static IP source guard binding entries and the DHCP snooping entries. If a
match is found from those entries, the ARP packet is considered valid and is forwarded. If no match is
found, the ARP packet is considered invalid and is discarded.