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Articles on networking, security and the internet.
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A, AAAA, CNAME and MX: Separate DNS records
DNS is not just about translating the domain name into an IP address. Querying different record types separately avoids confusing web and email issues.
DNS TTL: why is the change not visible immediately?
After changing the DNS record, not everyone may see the same result at the same time. TTL and cache layers are essential parts of planning migration.
NXDOMAIN, SERVFAIL and timeout are not the same thing
Recording the exact type of DNS error changes the resolution. Not being able to find a name, not being able to answer the server, and not getting a response at all are different situations.
What does DNSSEC verify and not encrypt?
DNSSEC and encrypted DNS solve different problems. When evaluating the accuracy of name resolution, it is necessary to separate data source authentication from transport confidentiality.
DoH and DoT: two transport methods for encrypted DNS
DNS over HTTPS and DNS over TLS serve to transport encrypted queries between the client and the resolver. Knowing which one is used is important during diagnosis.
Does a reverse DNS record prove the real name of the device?
The DNS name appearing next to an IP address makes the inventory readable; but it is not definitive proof of device identity. Maintain the origin and currency of the name.
Why don't mDNS and .local names appear on every network?
The printer or media device may appear in one room with a .local name but not in another VLAN. Understanding the scope of local discovery prevents mistaking it for a device malfunction.
Service discovery with DNS-SD: name, port and destination together
Knowing the device's IP address does not always tell you which port the service it offers is located on. DNS-SD records can present service information in a more structured format.
DNS does not use UDP 53 only
Checking only UDP access for DNS is an incomplete diagnostic. Due to situations requiring TCP, some queries may work while others may fail.
Windows network diagnostics: top five read-only checks
When a network problem occurs, save the current status first instead of resetting all settings. Five simple checks distinguish whether the problem is at the local link, route, DNS or application layer.
MTU issue: why does the large transfer get stuck while the small request is running?
Partial opening of a page or major transmission interruption over VPN may be related to packet size. Conduct MTU probe separate from DNS and service access.
7 Ways to Improve Your Internet Speed
Practical tips to fix slow internet: router placement, DNS settings and more.