Forwarding Table 편집하기

'''Forwarding Table''' is a data structure used by network devices, such as routers and switches, to determine the next hop or output interface for forwarding packets. It plays a crucial role in the data plane, enabling efficient and accurate packet forwarding based on precomputed rules.
==Overview==
The forwarding table maps packet header information, such as destination IP addresses or MAC addresses, to specific output ports or next-hop devices. It is typically built using information from the routing table (in the control plane) and other protocols, such as ARP (Address Resolution Protocol) or VLAN tagging.
==Key Features==
*'''High-Speed Lookup:''' Forwarding tables are optimized for rapid lookup operations to meet real-time data forwarding requirements.
*'''Compact Representation:''' They use efficient data structures, such as trie-based trees or hash tables, to minimize memory usage.
*'''Dynamic Updates:''' Forwarding tables are updated dynamically as network conditions change, such as when routes are added or removed.
==Structure==
A typical forwarding table entry includes:
*'''Destination Address:''' The destination IP or MAC address of the packet.
*'''Prefix Length:''' In IP forwarding, this indicates the subnet or network range.
*'''Next Hop:''' The address or identifier of the next device in the path.
*'''Output Interface:''' The network interface through which the packet should be forwarded.
*'''Metric (Optional):''' A value indicating the cost of the route, used for decision-making in multi-path scenarios.
Example Forwarding Table:
{| class="wikitable"
!Destination Network!!Prefix Length!!Next Hop!!Output Interface
|-
|192.168.1.0||24||10.0.0.1||eth0
|-
|10.0.0.0||16||10.0.1.1||eth1
|-
|0.0.0.0||0||10.0.2.1||eth2
|}
==Relationship to [[Routing Table]]==
*The routing table exists in the control plane and stores all potential routes learned from routing protocols or static configurations.
*The forwarding table is derived from the routing table and is used in the data plane for real-time packet forwarding.
*Forwarding tables are smaller and optimized for lookups compared to routing tables, which store more extensive information.
==Applications==
*'''Routers:''' Forwarding tables guide IP packets to the appropriate next hop in a routed network.
*'''Switches:''' Used for MAC address forwarding in Layer 2 networks.
*'''SDN Devices:''' Forwarding tables are dynamically programmed by the SDN controller to implement specific traffic policies.
==Advantages==
*Ensures efficient and accurate packet delivery.
*Reduces complexity by abstracting real-time forwarding decisions.
*Supports scalability by maintaining only active paths and routes.
==Limitations==
*Requires constant synchronization with the routing table to handle network changes.
*High-speed lookups can be resource-intensive in large-scale networks.
*Forwarding tables are specific to the data plane and cannot make high-level routing decisions.
==See Also==
*[[Routing Table]]
*[[Data Plane]]
*[[Control Plane]]
*[[Software-Defined Networking (SDN)]]
*[[Switching]]
[[Category:Network]]
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