Usage of router

Routers are network devices that operate at the network layer (Layer 3) of the OSI model. They are used to connect multiple networks together and facilitate the exchange of data between these networks. Routers perform the following important functions:

1. Packet forwarding: Routers examine the destination IP address of incoming packets and make forwarding decisions based on routing tables. They determine the optimal path for packets to reach their destination across different networks.

2. Network addressing: Routers use IP addresses to identify and route packets. They enable communication between devices on different networks by forwarding packets between networks based on IP addressing schemes.

3. Network segmentation: Routers can divide a large network into smaller subnets, allowing for better organization and management of network resources. Each subnet can have its own IP address range, subnet mask, and network devices.

4. Interconnectivity: Routers provide connectivity between different types of networks, such as connecting a local area network (LAN) to the internet or connecting multiple LANs together. They enable devices on different networks to communicate with each other.

5. Network security: Routers can implement various security features, such as firewall functionality, access control lists (ACLs), and network address translation (NAT), to protect networks from unauthorized access and control the flow of traffic.

6. Path selection and routing protocols: Routers use routing protocols, such as OSPF (Open Shortest Path First) or BGP (Border Gateway Protocol), to exchange routing information with other routers and dynamically determine the best paths for forwarding packets.

Overall, routers play a crucial role in directing network traffic, connecting networks, and ensuring efficient and secure data transmission between devices and networks.

static route

A static route is a manually configured route in a router's routing table that specifies the path to reach a specific network or destination. Unlike dynamic routing protocols that automatically exchange routing information between routers, static routes are manually configured by a network administrator.

Static routes are typically used in small networks or for specific routing requirements where a particular network needs to be reached through a specific next-hop router or interface. They provide a fixed path for forwarding packets and do not dynamically adapt to changes in the network topology.

When a router receives a packet with a destination IP address, it checks its routing table to determine the appropriate next-hop for forwarding the packet. If a static route exists for the destination network, the router will use the specified next-hop router or interface to forward the packet. If there is no matching static route, the router will use its default route or rely on dynamic routing protocols to find a suitable route.

Static routes offer simplicity and control over network routing. They can be useful for connecting isolated networks, defining backup routes, or overriding the default routing behavior. However, static routes require manual configuration and do not provide automatic adaptation to network changes, so they may not be suitable for large or dynamic networks.

It's worth noting that the configuration syntax for static routes may vary depending on the router's operating system or vendor.

自主学习的是，动态路由。静态路由更稳定，可以避免arp攻击。

静态路由配置

ip route network  [mask] {address | interface} [distance] [permanent]

The "ip route" command with the specified syntax is used to configure a static route on a router. Here's an explanation of each parameter:

• network: This specifies the destination network or subnet you want to reach. It can be either an IP network address or a specific IP address.
• mask: This is an optional parameter that specifies the subnet mask associated with the destination network. If not provided, the command assumes a classful network mask based on the IP address provided.
• address: This parameter specifies the IP address of the next-hop router or the exit interface through which the router should forward the traffic to reach the destination network.
• interface: This parameter specifies the exit interface through which the router should forward the traffic to reach the destination network. Instead of specifying a specific next-hop IP address, you can use the exit interface directly.
• distance: This is an optional parameter that sets the administrative distance for the static route. The administrative distance determines the reliability or trustworthiness of a particular routing source. If not specified, the default administrative distance is used.
• permanent: This is an optional parameter that makes the static route permanent, meaning it remains in the routing table even if the router is restarted.

Address 下一跳路由器的IP地址

Interface 本地路由器的出站接口

The "ip route" command is used to configure static routes on a router. The exact syntax may vary depending on the router's operating system, but here is a general example of how to use the "ip route" command:

To add a static route:

ip route <destination_network> <subnet_mask> <next_hop>

• <destination_network> is the network or destination you want to reach.
• <subnet_mask> is the subnet mask associated with the destination network.
• <next_hop> is the IP address or exit interface through which the router should forward the traffic to reach the destination network.

For example, let's say you want to add a static route to the network 192.168.2.0/24 via the next-hop IP address 10.0.0.1:

ip route 192.168.2.0 255.255.255.0 10.0.0.1

To remove a static route, you can use the "no" form of the command followed by the same parameters used when adding the route:

Remember to adjust the syntax based on the specific router's operating system you are working with, as the command syntax may vary. It's recommended to consult the router's documentation or command reference for accurate information on how to use the "ip route" command on your specific router.

交换机连线之后，先红色，后面再自动绿色。

路由器连线之后，默认都是红色。