What should I do if DNS is paralyzed? Detailed explanation of cause investigation and quick recovery plan

in daily network use and enterprise operation and maintenance, DNS paralysis is a problem that can easily lead to large-scale network failures. Small individuals cannot open web pages, and large enterprises can disrupt the whole line of business, which will have a serious impact on users. Many people are often at a loss when encountering such problems, and do not know where to start to investigate and solve them. This article will provide you with a comprehensive and practical solution from the cause of DNS paralysis, emergency recovery to long-term prevention, to help you deal with similar problems calmly.

What are the common triggers of DNS paralysis?

to solve the problem of DNS paralysis, it is first necessary to clarify the triggering reasons, and the corresponding solutions for different reasons are quite different.

1, local DNS server failure

this is one of the common causes of DNS paralysis. The local DNS server may fail due to hardware damage, system crash, resource exhaustion, etc., resulting in the inability to resolve the domain name normally. For example, the default local DNS service process of the personal computer is unexpectedly terminated, or the hard disk of the enterprise's own DNS server fails, which will directly cause the DNS paralysis problem.

2 Cyber attacks

today's network attacks are diverse, DDoS attacks, domain hijacking, etc. may lead to DNS paralysis. Attackers occupy DNS server resources by sending a large number of invalid requests, or tamper with domain name resolution points, so that normal domain name resolution requests cannot be responded correctly, and eventually lead to DNS paralysis.

3, network link interruption

when the network link between the user equipment and the DNS server is interrupted, such as optical fiber is cut off, router failure, etc., will lead to domain name resolution request can not be delivered to the server, but also the symptoms of DNS paralysis, in this case is not the server itself failure, but the transmission channel problems.

How to quickly troubleshoot the root cause of DNS paralysis?

when the network cannot resolve the domain name normally, it needs to be quickly checked through a series of steps to determine whether the DNS is paralyzed and the specific root cause of the problem.

1, basic network connectivity testing

first of all, you can verify the network connectivity through the ping public network Internet Protocol Address. If you can ping normally, it means that the network link is basically normal, and the high probability is the domain name resolution problem caused by DNS paralysis; if you can't ping, it may be a network link failure. You need to check the network connection first, and then confirm whether there is DNS paralysis.

2, replace the DNS server test

replace the DNS server address of the device with public DNS, such as domestic 114.114.114.114 or foreign 8.8.8.8, if the domain name can be resolved normally after replacement, indicating that there is a problem with the original DNS server, which is the direct cause of DNS paralysis; if it cannot be resolved after replacement, it may be a network attack or a lower-level network failure.

3, check the local DNS service status

for individual users, you can check whether DNS-related services are running normally in the system service; for enterprise users, you can log in to build your own DNS server to view the server process and resource occupation, and analyze whether there are abnormal requests through logs to determine whether DNS is paralyzed due to local service abnormalities.

What are the emergency recovery plans after DNS paralysis?

after identifying the root cause of DNS failure, emergency recovery measures need to be taken immediately to shorten the duration of the failure as much as possible and reduce the scope of impact.

1 Switch to an alternate DNS server

this is the fastest emergency response to DNS paralysis, individual users can switch directly to the public DNS server in the network settings, and enterprise users can switch to the pre-configured standby self-built DNS server to ensure that the domain name resolution function is quickly restored.

2, repair local DNS service failure

if the DNS paralysis is caused by the termination of the local DNS service process, individual users can restart the relevant system services, enterprise users can restart the DNS service process on the server; if caused by hardware failure, you need to replace the damaged hardware equipment in time, and you can temporarily use the standby server to maintain service, and then switch back after hardware repair.

3, intercept network attack recovery analysis

if the DNS paralysis is caused by a network attack, it is necessary to immediately start the firewall's attack interception rules to filter abnormal requests, and contact the network service provider to assist in cleaning traffic to prevent the attack from continuing to affect the DNS server. For DNS paralysis caused by domain name hijacking, it is necessary to modify the domain name resolution record in time to restore the correct resolution direction.

How to prevent DNS paralysis from happening again?

solve the problem of DNS paralysis, it is also necessary to do a long-term prevention to reduce the probability of DNS paralysis from the root cause and avoid repeated failures.

1, build a multi-DNS server architecture

enterprise users can build the main and standby DNS server architecture, when the main server failure causes DNS paralysis, the standby server can automatically take over the service to ensure that the domain name resolution is not interrupted; individual users can also configure multiple DNS server addresses in the network settings, The system will automatically switch the available servers.

2, strengthen DNS server security protection

regularly strengthen the security of DNS servers, install firewalls, intrusion detection systems, and timely update system patches to prevent attackers from exploiting vulnerabilities to cause DNS paralysis. At the same time, limit the source of DNS server requests, monitor and intercept abnormal requests in real time, and reduce the probability of successful network attacks.

3, regular DNS service inspection

individual users can regularly check whether the DNS configuration in the network settings is normal, enterprise users need to establish a regular inspection mechanism to check the hardware status, resource occupation, and service process operation of the DNS server, and find potential hidden dangers in time to avoid large-scale DNS paralysis caused by small problems.

To sum up, DNS paralysis is a wide-ranging network failure, which is triggered by server failure, network attack, link interruption and other aspects. When DNS is paralyzed, it is necessary to quickly investigate the root cause through basic testing, server switching and other methods, and then take emergency plans such as switching backup servers and repairing local services to restore the network. Finally, long-term prevention can be done by building a multi-server architecture and strengthening security protection to minimize the impact of DNS paralysis and ensure the stable operation of the network.