UMN:CLI
User Manual
V5824G
280
8.5.1.13
Authorized ARP
The authorized ARP is to limit the lease of IP addresses to authorized users. This feature
enables a DHCP server to add ARP entries only for the IP addresses currently in lease
referring to a DHCP lease table, discarding ARP responses from unauthorized users (e.g.
an illegal use of a static IP address).
When this feature is running, dynamic ARP learning on an interface will be disabled, since
DHCP is the only authorized component currently allowed to add ARP entries.
The authorized ARP is enabled only in a DHCP server.
To limit the lease of IP addresses to authorized users, use the following command.
Command
Mode
Description
ip dhcp authorized-arp
start
<120-2147483637>
timeout
<120-
2147483637>
Global
Discards an ARP response from unauthorized user.
start: starting time (default: 3600 sec)
timeout: expire time
ip dhcp authorized-arp
<120-
2147483637>
Discards an ARP response from unauthorized user.
120-2147483637: expire time
no ip dhcp authorized-arp
Disables the authorized ARP function.
You can verify the valid and invalid list for the authorized ARP. The valid list includes the
IP addresses currently in lease, while the invalid list includes the IP addresses that send
ARP requests, but not in lease. Both lists include IP addresses of a DHCP pool, but the
authorized ARP only allows the ARP response of the IP addresses in the valid list.
To display entries of the valid and invalid lists, use the following command.
Command
Mode
Description
show ip dhcp authorized-arp
valid
Enable
Global
Bridge
Shows entries of the valid list.
show ip dhcp authorized-arp
invalid
Shows entries of the invalid list.
To delete entries of the invalid list, use the following command.
Command
Mode
Description
clear ip dhcp authorized-arp
invalid
Enable
Global
Bridge
Deletes entries of the invalid IP addresses.
8.5.1.14
Prohibition of 1:N IP Address Assignment
The DHCP server may assign plural IP addresses to a single DHCP client in case of
plural DHCP requests from the DHCP client, which has the same hardware address.
Some network devices may need plural IP addresses, but most DHCP clients like
personal computers need only a single IP address. In this case, you can configure the
V5824G to prohibit assigning plural IP addresses to a single DHCP client.
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