Network Router User Manual

SmartSwitch Router User Reference Manual 81
Chapter 8: IP Routing Configuration Guide
Configuring Address Resolution Protocol (ARP)
The SSR allows you to configure Address Resolution Protocol (ARP) table entries and
parameters. ARP is used to associate IP addresses with media or MAC addresses. Taking
an IP address as input, ARP determines the associated MAC address. Once a media or
MAC address is determined, the IP address/media address association is stored in an
ARP cache for rapid retrieval. Then the IP datagram is encapsulated in a link-layer frame
and sent over the network.
Configuring ARP Cache Entries
To create an ARP entry for the IP address 10.8.1.2 at port et.4.7 for 15 seconds:
To create a permanent ARP entry for the host nfs2 at port et.3.1:
To remove the ARP entry for the host 10.8.1.2 from the ARP table:.
To clear the entire ARP table.
If the Startup configuration file contains arp add commands, the Control Module re-adds
the ARP entries even if you have cleared them using the arp clear command. To
permanently remove an ARP entry, use the negate command or no command to remove
the entry.
Unresolved MAC Addresses for ARP Entries
When the SSR receives a packet for a host whose MAC address it has not resolved, the SSR
tries to resolve the next-hop MAC address by sending ARP requests. Five requests are
sent initially for each host, one every second.
You can configure the SSR to drop packets for hosts whose MAC addresses the SSR has
been unable to resolve. To enable dropping of packets for hosts with unresolved MAC
addresses:
ssr# arp add 10.8.1.2 mac-addr 08:00:20:a2:f3:49 exit-port et.4.7 keep-time 15
ssr(config)# arp add nfs2 mac-addr 080020:13a09f exit-port et.3.1
ssr# arp clear 10.8.1.2
ssr# arp clear all
ssr# arp set drop-unresolved enabled