Analysis and Solution of IP conflicts between wireless routers and modem (home Internet access)

Overview: analyzes and solves some problems when accessing the internet at home.

I. Wireless routers

A wireless router is used for accessing the Internet and providing wireless coverage.

A wireless router can be used as a forwarder to forward the broadband network signal received from the home wall to nearby wireless network devices (laptops, WiFi-enabled mobile phones, etc.) through an antenna ).

Popular wireless routers in the market generally support four access methods: XDSL/cable, dynamic XDSL, and PPTP. It also has other network management functions, such as DHCP service, NAT firewall, and MAC address filtering.

A wireless router is an extended product that combines a simple Wireless AP and a Broadband Router, it not only provides all functions of simple Wireless AP, such as supporting DHCP clients, VPN, firewall, WEP encryption, but also includes the Network Address Translation (NAT) function, supports network connection sharing for LAN users. Internet connections in the home wireless network can be shared to achieve wireless shared access between ADSL, cable modem, and residential broadband. A wireless router can be directly connected to all Ethernet-connected ADSL modem or cable modem. It can also be accessed through a LAN such as a switch/hub or a Broadband Router. It has built-in Simple Virtual dialing software that can store user names and passwords for dial-up Internet access. It can provide automatic dialing functions for dial-up Internet access ADSL and CM, you do not need to manually dial up or use a computer as a server. In addition, wireless routers generally provide more comprehensive security protection functions.

Ii. Modem

A modem (modem, modulator-demodulator), which is a digital signal modulated to the analog carrier signal for transmission, and demodulated the analog signal received to obtain digital information. Its goal is to generate analog signals that can be easily transmitted and restore the original digital data through decoding. Depending on the application scenario, the modem can use different means to transmit analog signals, such as using optical fiber, RF radio, or telephone lines.

The current modem is generally integrated with the router function.

Iii. Problems

When you access the Internet at home, the IP address of the wireless router conflicts with the modem, and the dynamic IP address cannot be assigned.

Iv. Solution

The networks used by modern homes are generally ADSL or optical fiber cables. They both have the following characteristics, both of them require mutual conversion between digital and analog signals or optical signals. Therefore, to achieve this conversion function, network operators generally use modem ).

In addition, modern homes often have multiple device interconnected networks, such as PCs and televisions. Therefore, if only modem can be used to connect a single device, however, you cannot connect multiple devices to the network. To solve this problem, modem is generally integrated with the functions of the router. In this way, the modem is connected to the Internet and then routed to the Intranet.

Generally, when we need to set up a wireless network, the wireless router is set to an Internet-Intranet-Wireless WiFi Intranet process.

 

Through such a simple analysis, we can try to solve the above problems.

First, the IP address conflict between the wireless router and the modem. The cause of the conflict is that the default network segment of the wireless router is the same as the default network segment of the modem, and the same network is 192.168.1.0/24. In this way, when we try to access the vro configuration interface, the link 192.168.1.1 will usually jump to the telecom service interface, rather than the vro configuration interface. Then, how can I configure the router setting interface and the telecom service interface that can be accessed at the same time?

The solution is to reset the IP address on the vro settings page. This setting process must be performed on the vro settings page. If you cannot enter the vrowan configuration interface, the solution is to disconnect the WAN port of the vrowan and enter 192.168.1.1 again. If you cannot enter the vro configuration interface, press the reset key of the vroreto reset the vro, then enter 192.168.1.1. Generally, you can go to the vro configuration interface (if not, we do not know how to solve it ).

After entering the vro settings page, set the IP address of the LAN on the network parameter-LAN port. The settings page is as follows:

 

Reset the basic network parameters of the LAN port at the IP address and subnet mask. How do I set these network parameters? There are many ways to set IP addresses. You only need to combine the IP address and subnet mask to separate the network segments of the wireless router and modem. Here, I use the IP address 192.168.2.1 and the subnet mask 255.255.255.0 for reference only.

After the configuration is complete, restart the vro and enter the new IP address 192.168.2.1 To Go To The vro configuration page. In this way, configure the router step by step according to the setting wizard according to your individual needs.

Then, we will discuss the problem that dynamic IP addresses cannot be allocated (Wan settings ).

Because the dynamic IP address is used in the network mode, the WAN port connection type is selected in the WAN port setting interface. For such connection mode, you do not need to enter the Internet user name and password, the network operator always keeps the connection established. When a device accesses the network through this link, the carrier server automatically assigns an IP address to the device. Generally, only one IP address is assigned for the service. Of course, for other Internet access methods, such as ADSL and pppoe, you only need to enter the user name and password as prompted to achieve remote login.

Here, there are several notes for the setting interface.

1. Why is the IP address assigned by the wireless router (Wireless AP) 192.168.1.3?

2. Why is the gateway 192.168.1.1?

3. Why is the DNS server 192.168.1.1?

Now, solve the above problems in sequence.

 

1. In the middle, we can see that the devices in the AP network are separated by two networks, one being the AP network and the other being the modem network. The IP address of the Wireless AP in the modem network is allocated to the router in the modem. Because the network segment of the modem network is 192.168.1.0/24, the IP address of the Wireless AP is allocated to 192.168.1.3, that is, the modem network. Meanwhile, the network mask is 255.255.255.0.

2. First, we need to understand what the gateway here refers. This is for the WAN port setting of the Wireless AP, so we should consider the modem network. Therefore, the device connected to the Internet is the gateway. We know that the IP address of the modem and the router is 192.168.1.1. Therefore, the gateway of the Wireless AP in the modem network is 192.168.1.1.

3. DNS is the Domain Name Server. The function of this server is to convert the domain name that we usually use, such as the www.nba.com string domain name, to the IP address that marks the host in the network, or IPv4, or IPv6. The DNS server here refers to the IP address that the Wireless AP should send a DNS request to when it receives a domain name. Because the Wireless AP is in the modem LAN, all external information is abstracted as gateway information. When any network request is sent to the device in the network, the gateway device takes over the information and runs related processing routines. Similarly, when a Wireless AP has a DNS request, you only need to send the request to the gateway, and other operations are completed by the gateway. Therefore, the IP address of the DNS server corresponding to the Wireless AP is 192.168.1.1.

Here, it is necessary to verify the information about the AP network for the network diagram above.

 

It is related to the wireless network connection of a laptop connected to the AP network. We can see that the IP address is the IP address in the AP network segment, and the default gateway is the IP address of the AP in the AP network, that is, 192.168.2.1, And the DNS server address is 192.168.2.1, the default gateway of the AP network.

The reason why Dynamic IP addresses cannot be allocated is described. The initial reason why Dynamic IP addresses cannot be allocated is that I set the IP address of the LAN port of the wireless router to 192.168.1.10 and the subnet mask to 255.255.255.0. This is why IP addresses cannot be allocated. When I set the LAN port of the wireless router to 192.168.1.10 and the subnet mask to 255.255.255.0, the AP network segment of the wireless router is the same as that of the modem network, this will cause the modem network to fail to assign an IP address to the Wireless AP. Because the AP has the same Intranet and Internet CIDR blocks, it will not know which network the IP address is allocated, when an IP address is assigned to the AP on the Internet, the AP will find that the IP address conflicts with the Intranet address and block this operation. As a result, the AP can never be assigned an IP address and cannot access the Internet.

Therefore, the key here is to ensure that the network segments of the two subnets are inconsistent. Although the CIDR block of 192.168.0.0/16 is a dedicated address, two connected subnets cannot use the same CIDR Block (even a dedicated address ).