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Local Proxy ARP
The Local Proxy ARP feature is an extension of the Proxy ARP feature, but is enabled on an IP interface
and applies to the VLAN bound to that interface. When Local Proxy ARP is enabled, all ARP requests
received on VLAN member ports are answered with the MAC address of the IP interface that has Local
Proxy ARP enabled. In essence, all VLAN traffic is now routed within the VLAN instead of bridged.
This feature is intended for use with port mapping applications where VLANs are one-port associations.
This allows hosts on the port mapping device to communicate via the router. ARP packets are still bridged
across multiple ports.
Note that Local Proxy ARP takes precedence over any switch-wide Proxy ARP or ARP function. In addi-
tion, it is not necessary to configure Proxy ARP in order to use Local Proxy ARP. The two features are
independent of each other.
By default, Local Proxy ARP is disabled when an IP interface is created. To enable this feature, use the
interface
command. For example:
-> ip interface Accounting local-proxy-arp
Note that when Local Proxy ARP is enabled for any one IP router interface associated with a VLAN, the
feature is applied to the entire VLAN. It is not necessary to enable it for each interface. However, if the IP
interface that has this feature enabled is moved to another VLAN, Local Proxy ARP is enabled for the new
VLAN and must be enabled on another interface for the old VLAN.
ARP Filtering
ARP filtering is used to determine whether or not the switch responds to ARP requests that contain a
specific IP address. This feature is generally used in conjunction with the Local Proxy ARP application;
however, ARP filtering is available for use on its own and/or with other applications.
By default, no ARP filters exist in the switch configuration. When there are no filters present, all ARP
packets are processed, unless they are blocked or redirected by some other feature.
Use the
arp filter
command to specify the following parameter values required to create an ARP filter:
•
An IP address (e.g., 193.204.173.21) used to determine whether or not an ARP packet is filtered.
•
An IP mask (e.g. 255.0.0.0) used to identify which part of the ARP packet IP address is compared to
the filter IP address.
•
An optional VLAN ID to specify that the filter is only applied to ARP packets from that VLAN.
•
Which ARP packet IP address to use for filtering (sender or target). If the target IP address in the ARP
packet matches a target IP specified in a filter, then the disposition for that filter applies to the ARP
packet. If the sender IP address in the ARP packet matches a sender IP specified in a filter, then the
disposition for that filter applies to the ARP packet.
•
The filter disposition (block or allow). If an ARP packet meets filter criteria, the switch is either
blocked from responding to the packet or allowed to respond to the packet depending on the filter
disposition. Packets that do not meet any filter criteria are responded to by the switch.
The following arp filter command example creates an ARP filter, which blocks the switch from respond-
ing to ARP packets that contain a sender IP address that starts with 198:
-> arp filter 198.0.0.0 mask 255.0.0.0 sender block
page 1114
OmniSwitch AOS Release 7 Network Configuration Guide
ip
March 2011
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