Configure Arp - NETGEAR S3300 User Manual

Configure ARP

The address resolution protocol (ARP) associates a layer 2 MAC address with a layer 3 IPv4
address. Switch software features both dynamic and manual ARP configuration. With manual
ARP configuration, you can statically add entries into the ARP table.
ARP is a necessary part of the Internet protocol (IP) and is used to translate an IP address to
a media (MAC) address, defined by a local area network (LAN) such as Ethernet. A station
needing to send an IP packet must learn the MAC address of the IP destination, or of the next
hop router, if the destination is not on the same subnet. This is achieved by broadcasting an
ARP request packet, to which the intended recipient responds by unicasting an ARP reply
containing its MAC address. Once learned, the MAC address is used in the destination
address field of the Layer 2 header prepended to the IP packet.
The ARP cache is a table maintained locally in each station on a network. ARP cache entries
are learned by examining the source information in the ARP packet payload fields,
regardless of whether it is an ARP request or response. Thus, when an ARP request is
broadcast to all stations on a LAN segment or virtual LAN (VLAN), every recipient has the
opportunity to store the sender's IP and MAC address in their respective ARP cache. The
ARP response, being unicast, is normally seen only by the requestor, who stores the sender
information in its ARP cache. Newer information always replaces existing content in the ARP
cache.
The switch supports 512 ARP entries, which includes dynamic and static ARP entries.
Devices can be moved in a network, which means the IP address that was at one time
associated with a certain MAC address is now found using a different MAC address, or can
have disappeared from the network altogether (in other words, it has been reconfigured,
disconnected, or powered off). This leads to stale information in the ARP cache unless
entries are updated in reaction to new information seen on the network, periodically
refreshed to determine if an address still exists, or removed from the cache if the entry has
not been identified as a sender of an ARP packet during the course of an ageout interval,
usually specified via configuration.
To configure and display ARP details, see the following sections:
• ARP Cache on page 220
• Create a Static ARP Entry
• Configure Global ARP Settings
• Remove an ARP Entry From the ARP Cache
S3300 Smart Managed Pro Switch
on page 221
on page 221
on page 222
Configuring Routing
219