Difference between revisions of "Manual:IP/ARP"

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{{Versions|2.9, v3, v4}}
{{Versions|2.9, v3, v4 +}}


<div class=manual>
<div class=manual>


<h2>Summary</h2>
==Summary==
<p><b>Sub-menu:</b> <code>/ip arp</code></p>
<p id="shbox"><b>Sub-menu:</b> <code>/ip arp</code><br />
<p><b>Standards:</b> <code>ARP RFC 826</code></p>
<p><b>Standards:</b> <code>ARP RFC 826</code>
</p>
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<br />
<p>
<p>
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</p>
</p>


<h2>Properties</h2>
==Properties==


<table class="styled_table">
<table class="styled_table">
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</tr>
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Read only properties
Read only properties
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<h2>Notes</h2>
{{ Note |
Maximal number of ARP entries is 8192.
Maximal number of ARP entries is 8192.
}}


<h2>ARP Modes</h2>
==ARP Modes==


It is possible to set several ARP modes in interface configuration .....
It is possible to set several ARP modes in interface configuration .....


<h3>Disabled</h3>
===Disabled===
If ARP feature is turned off on the [[Interface/General | interface]], i.e., arp=disabled is used, ARP requests from clients are not answered by the router. Therefore, static arp entry should be added to the clients as well. For example, the router's IP and MAC addresses should be added to the Windows workstations using the arp command:
If ARP feature is turned off on the [[Interface/General | interface]], i.e., arp=disabled is used, ARP requests from clients are not answered by the router. Therefore, static arp entry should be added to the clients as well. For example, the router's IP and MAC addresses should be added to the Windows workstations using the arp command:
<pre>
<pre>
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</pre>
</pre>


<h3>Enabled</h3>
===Enabled===
This mode is enabled by default on all interfaces. ARPs will be discovered automatically and new dynamic entries will be added to ARP table.
This mode is enabled by default on all interfaces. ARPs will be discovered automatically and new dynamic entries will be added to ARP table.


<h3>Proxy ARP</h3>
===Proxy ARP===
A router with properly configured proxy ARP feature acts like a transparent ARP proxy between directly connected networks.
A router with properly configured proxy ARP feature acts like a transparent ARP proxy between directly connected networks.
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This behaviour can be usefull, for example, if you want to assign dial-in (ppp, pppoe, pptp) clients IP addresses from the same address space as used on the connected LAN.
This behaviour can be usefull, for example, if you want to assign dial-in (ppp, pppoe, pptp) clients IP addresses from the same address space as used on the connected LAN.


<h3>Reply Only</h3>
===Reply Only===


If arp property is set to <code>reply-only</code> on the interface, then router only replies to ARP requests. Neighbour MAC addresses will be resolved using /ip arp statically, but there will be no need to add the router's MAC address to other hosts' ARP tables like in case if arp is [[#Disabled | disabled]].
If arp property is set to <code>reply-only</code> on the interface, then router only replies to ARP requests. Neighbour MAC addresses will be resolved using /ip arp statically, but there will be no need to add the router's MAC address to other hosts' ARP tables like in case if arp is [[#Disabled | disabled]].

Revision as of 10:37, 30 April 2010

Version.png

Applies to RouterOS: 2.9, v3, v4 +

Summary

Sub-menu: /ip arp

Standards: ARP RFC 826


Even though IP packets are addressed using IP addresses, hardware addresses must be used to actually transport data from one host to another. Address Resolution Protocol is used to map OSI level 3 IP addreses to OSI level 2 MAC addreses. Router has a table of currently used ARP entries. Normally the table is built dynamically, but to increase network security, it can be partialy or completely built statically by means of adding static entries.

Properties

Property Description
address (IP; Default: ) IP address to be mapped
interface (name; Default: ) Interface name the IP address is assigned to
mac-address (MAC; Default: 00:00:00:00:00:00) MAC address to be mapped to


Read only properties

Property Description
DHCP (yes | no) True if arp entry is added by DHCP server
dynamic (yes | no) True if entry is dynamically created
invalid (yes | no) True if entry is not valid


Icon-note.png

Note: Maximal number of ARP entries is 8192.


ARP Modes

It is possible to set several ARP modes in interface configuration .....

Disabled

If ARP feature is turned off on the interface, i.e., arp=disabled is used, ARP requests from clients are not answered by the router. Therefore, static arp entry should be added to the clients as well. For example, the router's IP and MAC addresses should be added to the Windows workstations using the arp command:

C:\> arp -s 10.5.8.254  00-aa-00-62-c6-09

Enabled

This mode is enabled by default on all interfaces. ARPs will be discovered automatically and new dynamic entries will be added to ARP table.

Proxy ARP

A router with properly configured proxy ARP feature acts like a transparent ARP proxy between directly connected networks.
...
This behaviour can be usefull, for example, if you want to assign dial-in (ppp, pppoe, pptp) clients IP addresses from the same address space as used on the connected LAN.

Reply Only

If arp property is set to reply-only on the interface, then router only replies to ARP requests. Neighbour MAC addresses will be resolved using /ip arp statically, but there will be no need to add the router's MAC address to other hosts' ARP tables like in case if arp is disabled.