Impossible to escape: the first day of work after a long holiday, there will be customers to the network problems
The first day of the New Year to work, the most afraid of customers to say hello, because “happy New Year” next sentence, mostly “no network”, “network disk did not”, and even “the server can not boot” this sensational news.According to more than ten years of experience, every long vacation after the first day of work, there are always customers will report repair, help, and even dizzying situation – busy typing reply QQ and wechat, crooked neck also clamped mobile phone, and then said, forget who is the other end of the phone.Today until 10 o ‘clock, there is no customer news, thought today is so quiet and leisurely, is secretly happy, there are customers to repair, as expected, “Happy New Year, did you work?Some of our company computers are down.””Happy New Year” behind even a newline are not, repair directly in the back, it seems a little perfunctory ah, ha ha.However, we can not be perfunctory, hey hey, every customer’s every problem, should be treated seriously, as soon as possible.It is just “some computers are not connected to the Internet”. It must not be a big deal. While instructing customers to open “Local Connection” to check their IP addresses, customers can remotely log in to the Huawei firewall.DHCP has 2 IP addresses. The first one is a normal IP address. The second one starts with 169.254.Isn’t that the IP address that Windows automatically assigns when DHCP fails?Guide customer operation: right mouse button “local connection”, and then “disable”, 3 seconds later “enable”, re-view the details, this only a normal IP address, try to access the Internet, or failure, the web page can not be opened, QQ can not log in.Instruct the customer to open the CMD window and run the ping 10.1.2.1 command to test whether the Intranet is normal. The result shows that the user can reach the gateway quickly.Run the ping 10.1.2.2 command. The internal DNS server can also be pinged.Finally, run the ping 192.168.0.1 command to ping the Intranet interface of the firewall.Internal network communication is fine, need to check the exit equipment, take a look at huawei firewall.Someone might look at this and say, why not ping the external DNS server?Why not ping Baidu?In fact, there is no need to waste time, because it is definitely not through, if through, you can go on the Internet.Don’t you need to check the Intranet DNS server?- Of course not, because only some computers can’t access the Internet, and that has nothing to do with the Intranet DNS server.Similarly, the Layer 3 switch cannot be checked because the IP address of the Intranet interface on the firewall has been pinged.After logging in to the firewall, check whether the ports are working properly.It is obvious in the figure above that each interface is working properly and each broadband has obtained an IP address, indicating that the carrier links are also working well.In order to quickly check the problem, we temporarily put the VLAN that cannot access the Internet into another NAT policy, and then restore the original NAT policy, and then cannot access the Internet again.Back to the “interface” page, temporarily disabled the broadband interface that can not access the Internet, 3 seconds later to enable the interface, PPPOE dial-up again, and obtain a different IP address with just thought the problem solved, who knows the customer said, or can not access the Internet.Open the CLI console directly on the WEB page of the firewall and enter the command: ping -a 58.xx.xxx. 100 188.8.131.52.How is that possible?Switch to a broadband source, then ping the firewall no problem, so strange?What to do?Guide the customer to follow the network cable on the firewall interface to find the optical cat, restart the optical cat, and then the network is restored to normal, this……Ok, I admit, this is an extremely rare question that almost caused me to capsize in the gutter.– THE author is a network engineer, good at computer network field, entrepreneurship for many years, hope to share their experience to everyone, feel useful, you can pay attention to, like, forward, such as the same or different views, welcome comments.”Circle” has been opened recently, interested friends welcome to join the circle to study and discuss.