H3C Technologies H3C S12500 Series Switches - Manual (Page 133)

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Configuring adjacency table
The adjacency table feature only applies to hardware forwarding, but not software forwarding.
The adjacency table feature does not apply to Ethernet networks that use ARP for storing and managing
neighbor information.
You can only view adjacency entries on tunnel interfaces . For more information about tunnel interfaces,
see Layer 3—IP Services Configuration Guide.
Overview
Introduction to adjacency table
An adjacency table stores information about active neighbors, including neighbor network layer address
(next hop), output interface, link layer service type, and link layer address .
The concept of neighbor is relevant to network layer. Node B can be an IP neighbor, but not an IPX
neighbor of node A. Also, a neighbor in the active state is in relation to network layer. The adjacency
table feature only supports the neighbor concept in relation to IP.
A device can be connected with its neighbors through multiple link layer protocols.
The switch can apply the adjacency table to the drivers to implement hardware forwarding. In hardware
forwarding, the link layer header of the packet to be forwarded is quickly filled according to the
adjacency table, and then the packet is forwarded through the output interface.
Fields
Some fields in the adjacency table are described as follows:
• Routing interface—Outgoing interface in a route entry.
• Physical interface—An existing physical interface.
• Service type—Type of service corresponding to the adjacency table.
• Action type—Action to take on the packet that matches the entry, forward or drop.
• Link media type—Related to the link layer protocol used by the output interface.
• Link head information (IPv6)—Information about the link layer header corresponding to the IPv6
protocol.