3Com S7906E - Switch, Configuration Manual

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1-5
To do… Use the command… Remarks
Set the maximum number of
dynamic ARP entries that an
interface can learn
arp max-learning-num
number
Optional
8192 by default
Setting the Aging Time for Dynamic ARP Entries
To keep pace with the network changes, the ARP table is refreshed. Each dynamic ARP entry in the
ARP table has a limited lifetime rather than is always valid. Dynamic ARP entries that are not refreshed
before expiration are deleted from the ARP table. The lifetime is called the aging time. The aging time is
reset each time the dynamic ARP entry is refreshed within the lifetime. You can adjust the aging time for
dynamic ARP entries according to the actual network condition.
Follow these steps to set the aging time for dynamic ARP entries:
To do… Use the command… Remarks
Enter system view system-view —
Set the aging time for dynamic
ARP entries
arp timer aging aging-time
Optional
20 minutes by default.
Enabling the ARP Entry Check
The ARP entry check function disables the device from learning multicast MAC addresses. With the
ARP entry check enabled, the device cannot learn any ARP entry with a multicast MAC address, and
configuring such a static ARP entry is not allowed; otherwise, the system displays error messages.
After the ARP entry check is disabled, the device can learn the ARP entry with a multicast MAC address,
and you can also configure such a static ARP entry on the device.
Follow these steps to enable the ARP entry check:
To do… Use the command… Remarks
Enter system view system-view —
Enable the ARP entry check arp check enable
Optional
By default, the device is disabled from
learning multicast MAC addresses.
Enabling the Support for ARP Requests from a Natural Network
When learning MAC addresses, if the device finds that the source IP address of an ARP packet and the
IP address of the inbound interface are not on the same subnet, the device will further judge whether
these two IP addresses are on the same natural network or not.
Suppose that the IP address of VLAN-interface 10 is 10.10.10.5/24 and that this interface receives an
ARP packet from 10.11.11.1/8. Because these two IP addresses are not on the same subnet,
VLAN-interface 10 cannot process the packet. With this feature enabled, the device makes a judgment
on natural network basis. Because the IP address of VLAN-interface 10 is a Class A address and its