A gateway is the "gateway" between the network and the network, which is the network level. A routing gateway is a device that accesses the Internet through a gateway. The gateway is also a path finding device that connects to different networks, that is, an outlet of the network where the device is located. It can communicate with both hosts at the same time, and direct communication between the two sides of the host is not acceptable.
Web environment:
Let's talk about the network environment. There are three servers, which are in the environment where network 1 and network 2 are completely isolated. Network 1 and network 2 cannot communicate with each other. Among them, Server1 is in network 1, Server3 is in network 2, and Server2 has two network cards, which are located in network 1 and network 2. Server3 cannot directly access Server1 because they are on different networks. To achieve the interconnection between the two servers, you must use the Server2 server. Server2 is regarded as a gateway. If Server3 wants to access Server1, it will send data to Server2 and then forward it to Server1 with Server2.
Specific configuration:
Server3 adds a route, and requests to access the 192.168.100. network segment are sent to Server2. But I thought they could only pass the 109.105.115. network segment, so they must be set as follows:
You can observe that the route of the 192.168.100.* network segment has been added to the routing table, and then configure Server2. The NICs in Server2 are as follows:
At this point, if you ping Server1 directly in Server3, it is still unreasonable, but using the tcpdump command in Server2, it is found that the data has indeed been sent to Server2.
Then, there is only one possibility, that is, the forwarding of Server2 fails, so it is necessary to open the forwarding function of Server2.
Ping Server1 directly in Server3, ping通, get it.
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire trucks. There are two general types: pneumatic and electronic.
Many fire sirens (used for calling the volunteer fire fighters) serve double duty as tornado or civil defense sirens, alerting an entire community of impending danger. Most fire
sirens are either mounted on the roof of a fire station or on a pole
next to the fire station. Fire sirens can also be mounted on or near
government buildings, on tall structures such as water towers,
as well as in systems where several sirens are distributed around a
town for better sound coverage. Most fire sirens are single tone and
mechanically driven by electric motors with a rotor attached to the
shaft. Some newer sirens are electronically driven speakers.
Fire sirens are often called "fire whistles", "fire alarms", or
"fire horns". Although there is no standard signaling of fire sirens,
some utilize codes to inform firefighters of the location of the fire.
Civil defense sirens also used as fire sirens often can produce an
alternating "hi-lo" signal (similar to emergency vehicles in many
European countries) as the fire signal, or a slow wail (typically 3x) as
to not confuse the public with the standard civil defense signals of
alert (steady tone) and attack (fast wavering tone). Fire sirens are
often tested once a day at noon and are also called "noon sirens" or
"noon whistles".
The first emergency vehicles relied on a bell. Then in the 70s,
they switched to a duotone airhorn. Then in the 80s, that was overtaken
by an electronic wail.
Piezo Alarm,Siren And Alarm,Piezo Buzzer Siren,Piezo Buzzer Alarm Siren
Jiangsu Huawha Electronices Co.,Ltd , https://www.hnbuzzer.com