Netgear GS728TP User Manual download pdf (Page 220)

Routing

220

ProSafe M5300 Switch

3. Use Subnet Mask to enter the Subnet Mask to be configured for the VLAN Routing

Interface.

4. Click ADD to add the VLAN Routing Interface specified in the VLAN ID field to the switch

configuration.

5. Click DELETE to remove the VLAN Routing Interface specified in the VLAN ID field from the

switch configuration.

Field Description

Port The interface assigned to the VLAN for routing.

MAC Address The MAC Address assigned to the VLAN Routing Interface

ARP

The ARP protocol associates a layer 2 MAC address with a layer 3 IPv4 address. ProSafe

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 number of supported ARP entries is platform-dependent.

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, or may have

disappeared from the network altogether (i.e., 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.

From the ARP link, you can access the following pages:

• Basic on page 221

• Advanced on page 221

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Netgear GS728TP User Manual Page 220