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Router

380 단어·2 분·원문(.md)

A router is a device that belongs to Layer 3 of the OSI 7-layer model, and its role is to set paths and deliver packets to other networks.

When a router sends a packet, if it cannot find the destination, it drops the packet.

Because the process of searching for a path to send data to the destination all at once is too difficult for a router, it designates an adjacent router as the destination, and that router then searches for the path again. This is called the hop-by-hop method.

Routers manage destinations to be routed in a table, which is called a routing table, and they search for the closest destination using the LPM method. (Longest Prefix Match)

Routers perform the following three functions.

  1. Path Determination: After collecting various paths, they send packets along the optimal path.
  2. Broadcast Control: If the destination address of an incoming packet is not in the routing table, the packet is discarded.
  3. Protocol Conversion: During the packet forwarding process, Layer 2 header information is removed and new header information is created.

Router Path Configuration #

There are three methods for routers to configure paths.

1. Directly Connected #

This method naturally obtains information about adjacent networks when an IP address is entered.

2. Static Routing #

This is a method where an administrator directly enters the destination IP into the routing table.

3. Dynamic Routing #

This is a method where routers automatically exchange path information with each other. It is also used for status exchange, indicating whether a router is currently able to receive packets.


Broadcast Control #

Routers generally do not acquire information via multicast and do not broadcast.

In other words, a router can only send packets if its own information is present in the routing table.

Networks that are directly connected can send information even without it.

This functionality is called Broadcast/Multicast Control.


Protocol Conversion #

Another role of a router is to connect networks configured with different protocols. However, this method has become less common as most networks currently use Ethernet. Examples include LAN and WAN.

When a packet arrives at a router, it strips off the Layer 2 header information, checks the Layer 3 address, and then creates new Layer 2 header information before sending it out.

Network/router.md