User guide

Configuring IP IP Forwarding
OmniSwitch 6600 Family Network Configuration Guide April 2005 page 13-11
Clearing Dynamic ARP Entries
Dynamic entries can be cleared using the clear arp-cache command. This command clears all dynamic
entries. Permanent entries must be cleared using the no arp command.
Use the show arp command to display the table and verify that the table was cleared.
Note. Dynamic entries remain in the ARP table until they time out. If the switch does not receive data
from a host for this user-specified time, the entry is removed from the table. If another packet is received
from this host, the switch goes through the discovery process again to add the entry to the table. The
switch uses the MAC Address table timeout value as the ARP timeout value. Use the mac-address-table
aging-time command to set the timeout value.
ARP Filtering
ARP filtering is used to determine whether or not the switch responds to ARP requests that contain a
specific IP address. 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 filetered.
• 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 will block the switch from responding 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
Up to 200 ARP filters can be defined on a single switch. To remove an individual filter, use the no form of
the arp filter command. For example:
-> no arp filter 198.0.0.0
To clear all ARP filters from the switch configuration, use the clear arp filter command. For example:
-> clear arp filter
Use the show arp filter command to verfiy the ARP filter configuration. For more informtion about this
and other ARP filter commands, see the OmniSwitch CLI Reference Guide.