D-Link DFL-260 Product Manual - Page 111

Published ARP Objects, Publishing Modes, publishing

Page 111 highlights

3.4.3. Creating ARP Objects 2. Select the following from the dropdown lists: • Mode: Static • Interface: lan 3. Enter the following: • IP Address: 192.168.10.15 • MAC: 4b-86-f6-c5-a2-14 4. Click OK Chapter 3. Fundamentals Published ARP Objects NetDefendOS supports publishing IP addresses on a particular interface, optionally along with a specific MAC address instead of the interfaces MAC address. NetDefendOS will then send out these as ARP replies for any ARP requests received on the interface related to the published IP addresses. This can done for a number of reasons: • To give the impression that an interface in NetDefendOS has more than one IP address. This is useful if there are several separate IP spans on a single LAN. The hosts on each IP span may then use a gateway in their own span when these gateway addresses are published on the corresponding NetDefendOS interface. • Another use is publishing multiple addresses on an external interface, enabling NetDefendOS to statically address translate traffic to these addresses and send it onwards to internal servers with private IP addresses. • A less common purpose is to aid nearby network equipment responding to ARP in an incorrect manner. Publishing Modes There are two publishing modes available when publishing a MAC/IP address pair: • Publish • XPublish In both cases, an IP address and an associated MAC address are specified. If the MAC address is not specified (is all zeroes) then the MAC address of the sending physical interface is used. To understand the difference between Publish and XPublish it is necessary to understand that when NetDefendOS responds to an ARP query, there are two MAC addresses in the Ethernet frame sent back with the ARP response: 1. The MAC address in the Ethernet frame of the Ethernet interface sending the response. 2. The MAC address in the ARP response which is contained within this frame. This is usually the same as (1) the source MAC address in the Ethernet frame but does not have to be. These are shown in the illustration below of an Ethernet frame containing an ARP response: 111

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2.
Select the following from the dropdown lists:
Mode:
Static
Interface:
lan
3.
Enter the following:
IP Address:
192.168.10.15
MAC:
4b-86-f6-c5-a2-14
4.
Click
OK
Published ARP Objects
NetDefendOS supports
publishing
IP addresses on a particular interface, optionally along with a
specific MAC address instead of the interfaces MAC address. NetDefendOS will then send out these
as ARP replies for any ARP requests received on the interface related to the published IP addresses.
This can done for a number of reasons:
To give the impression that an interface in NetDefendOS has more than one IP address.
This is useful if there are several separate IP spans on a single LAN. The hosts on each IP span
may then use a gateway in their own span when these gateway addresses are published on the
corresponding NetDefendOS interface.
Another use is publishing multiple addresses on an external interface, enabling NetDefendOS to
statically address translate traffic to these addresses and send it onwards to internal servers with
private IP addresses.
A less common purpose is to aid nearby network equipment responding to ARP in an incorrect
manner.
Publishing Modes
There are two publishing modes available when publishing a MAC/IP address pair:
Publish
XPublish
In both cases, an IP address and an associated MAC address are specified. If the MAC address is not
specified (is all zeroes) then the MAC address of the sending physical interface is used.
To understand the difference between
Publish
and
XPublish
it is necessary to understand that when
NetDefendOS responds to an ARP query, there are two MAC addresses in the Ethernet frame sent
back with the ARP response:
1.
The MAC address in the Ethernet frame of the Ethernet interface sending the response.
2.
The MAC address in the ARP response which is contained within this frame. This is usually
the same as (
1
) the source MAC address in the Ethernet frame but does not have to be.
These are shown in the illustration below of an Ethernet frame containing an ARP response:
3.4.3. Creating ARP Objects
Chapter 3. Fundamentals
111