Creating Arp Objects; Defining A Static Arp Entry - D-Link DFL-260E User Manual

3.4.3. Creating ARP Objects

Hash tables are used to rapidly look up entries in the ARP Cache. For maximum efficiency, a hash
table should be twice as large as the entries it is indexing, so if the largest directly connected LAN
contains 500 IP addresses, the size of the ARP entry hash table should be at least 1000. The
administrator can modify the ARP advanced setting ARP Hash Size to reflect specific network
requirements. The default value of this setting is 512.
The setting ARP Hash Size VLAN setting is similar to the ARP Hash Size setting, but affects the
hash size for VLAN interfaces only. The default value is 64.
3.4.3. Creating ARP Objects
To change the way NetDefendOS handles ARP on an interface, the administrator can create
NetDefendOS ARP objects, each of which has the following parameters:
Mode
Interface
IP Address
MAC Address
The three ARP modes of Static, Publish and XPublish are discussed next.
Static Mode ARP Objects
A Static ARP object inserts a particular MAC/IP address mapping into the NetDefendOS ARP
cache.
The most frequent use of static ARP objects is in situations where some external network device is
not responding to ARP requests correctly and is reporting an incorrect MAC address. Some network
devices, such as wireless modems, can have such problems.
It may also be used to lock an IP address to a specific MAC address for increasing security or to
avoid denial-of-service if there are rogue users in a network. However, such protection only applies
to packets being sent to that IP address. It does not apply to packets being sent from that IP address.
Example 3.15. Defining a Static ARP Entry
This example will create a static mapping between IP address 192.168.10.15 and Ethernet address
4b:86:f6:c5:a2:14 on the lan interface:
Command-Line Interface
gw-world:/> add ARP Interface=lan IP=192.168.10.15 Mode=Static
Web Interface
1. Go to Interfaces > ARP > Add > ARP
The type of ARP object. This can be one of:
• Static - Create a fixed mapping in the local ARP cache.
• Publish - Publish an IP address on a particular MAC address (or this
interface).
• XPublish - Publish an IP address on a particular MAC address and "lie" about
the sending MAC address of the Ethernet frame containing the ARP
response.
The local physical interface for the ARP object.
The IP address for the MAC/IP mapping.
The MAC address for the MAC/IP mapping.
MACAddress=4b-86-f6-c5-a2-14
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Chapter 3. Fundamentals