H3C Technologies H3C S12500 Series Switches - Manual (Page 102)

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Configuring adjacency table
The adjacency table stores information about directly connected neighbors for IP forwarding. The
command output only displays adjacency entries for Tunnel interfaces. For information about Tunnel
interfaces, see Layer 3—IP Services Configuration Guide.
The neighbor information is generated, updated, and deleted by link layer protocols (such as PPP or ATM)
through negotiation (such as PPP dynamic negotiation) or configuration (such as ATM static
configuration). An adjacency entry contains the neighbor network layer address (next hop), output
interface, link layer protocol type, and link layer address (PVC for ATM, unavailable for PPP).
During IP forwarding, a device checks the FIB to find the output interface and next hop, uses the output
interface and next hop address to obtain the link layer forwarding information including the link layer
protocol (such as PPP or HDLC), the media type (P2P or NBMA), and the link layer header information
in the adjacency table, and encapsulates and forwards the packet.
NOTE:
•
Ethernet neighbor information and non-Ethernet neighbor information are stored and managed
together. The adjacency table described in this chapter only manages non-Ethernet neighbor
information.
• The device operates in IRF or standalone (the default) mode. For information about IRF mode, see IRF
Configuration Guide.
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Adjacency table
Use the display adjacent-table command to display adjacency table entries. For example, display
detailed information about all IPv4 adjacency entries.
<Sysname> display adjacent-table all verbose
IP Address : 0.0.0.0
Routing Interface : Tunnel3
Physical Interface : Tunnel3
Logical Interface : N/A
Service Type : TUNNEL
Action Type : FORWARDING
Link Media Type : P2P
Slot : 1
Virtual Circuit Information : N/A
Link Head Information(IP) : ff030021
Link Head Information(MPLS) : ff030281
An adjacency entry mainly contains the following items:
• IP address—IP address of the next hop in FIB table for packet forwarding. This address is used for
adjacency table look up.
• Routing interface—Output interface in the matching route entry. This interface may be logical or
physical.