D-Link DGS-6600-48TS Configuration Guide - Page 167

Per Interface parameter, Sanity checks for ARP request, Acceptable route

Page 167 highlights

Volume 3-Layer 2 Configurations / Chapter 16-Proxy ARP Proxy ARP Configuration Commands Per Interface parameter The following parameters can configure the VLAN to enable proxy ARP or local proxy ARP. Parameter Name Proxy arp interface state Local proxy arp interface state Attribute Config/Show Default Value Disable Config/Show Disable Value Range Enable/ Disable Enable/ Disable Table 16-1 Configurable parameters Description Indicate if the interface enables proxy ARP Indicate if the interface enables local proxy ARP Sanity checks for ARP request According to RFC1027, there are some checks need to be done before Proxy ARP can reply. a)ARP for broadcast IP can not reply: If the gateway were to respond with an ARP reply in this situation, it would be inviting the original source to send actual traffic to a broadcast address. b)Must not reply if the physical networks of the source and target of an ARP request are the same. c)Must not reply if IP class of the source and target hosts of an ARP request are different. The same IP networks are local IP network. This is to prevent the ARP subnet gateway from being used to reach foreign IP networks and thus possibly bypass security checks provided by IP gateways. Acceptable route The following rules will be used to tell if the found route is acceptable. a)The default route must not be used while look up for route. If the default route were used, the system would always reply the ARP request, even if the system cannot forward the packets. b)If the network interfaces on which the request was received and through which the route to the target passes are the same, the gateway must not reply. The target host can answer for itself. Proxy ARP Configuration Commands Enabling Authentication To enable proxy-arp please use the following commands. Command ip local-proxy-arp DGS-6600 Configuration Guide Explanation Use this command to enable local proxy ARP features on an interface. Use the no form of this command to disable local proxy ARP features on an interface. 167

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Volume 3-Layer 2 Configurations / Chapter 16-Proxy ARP
Proxy ARP Configuration Commands
DGS-6600 Configuration Guide
167
Per Interface parameter
The following parameters can configure the VLAN to enable proxy ARP or local proxy ARP.
Sanity checks for ARP request
According to RFC1027, there are some checks need to be done before Proxy ARP can reply.
a)ARP for broadcast IP can not reply: If the gateway were to respond with an ARP reply in this
situation, it would be inviting the original source to send actual traffic to a broadcast address.
b)Must not reply if the physical networks of the source and target of an ARP request are the same.
c)Must not reply if IP class of the source and target hosts of an ARP request are different. The same
IP networks are local IP network. This is to prevent the ARP subnet gateway from being used to
reach foreign IP networks and thus possibly bypass security checks provided by IP gateways.
Acceptable route
The following rules will be used to tell if the found route is acceptable.
a)The default route must not be used while look up for route.
If the default route were used, the system would always reply the ARP request, even if the system
cannot forward the packets.
b)If the network interfaces on which the request was received and through which the route to the
target passes are the same, the gateway must not reply.
The target host can answer for itself.
Proxy ARP Configuration Commands
Enabling Authentication
To enable proxy-arp please use the following commands.
Parameter Name
Attribute
Default
Value
Value
Range
Description
Proxy arp interface state
Config/Show
Disable
Enable/
Disable
Indicate if the interface
enables proxy ARP
Local proxy arp interface state
Config/Show
Disable
Enable/
Disable
Indicate if the interface
enables local proxy
ARP
Table 16-1 Configurable parameters
Command
Explanation
ip local-proxy-arp
Use this command to enable local proxy ARP
features on an interface. Use the no form of this
command to disable local proxy ARP features
on an interface.