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10 votes
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How are IPv4 Addresses provided uniquely to domains?

Who mainly provides IP addresses to domains? As in, who commands, "www.google.com, 103.233.38.93 is yours; www.stackexchange.com I will assign 104.16.115.182 to you; etc." Normally IP addresses are ...
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9 votes

Is Reverse DNS part of the DNS protocol?

Reverse DNS for IPv4 is specified in RFC1035 Section 3.5. The special in-addr.arpa domain was created for this. For IPv6 the special domain is ip6.arpa as specified in RFC3596. The record type that ...
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8 votes
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Why can't I do a reverse DNS lookup on this IP address?

Short answer: There is not requirement that IP addresses provide a reverse lookup, so there are many IP addresses that do not have any reverse DNS lookup zone associated with them. Long answer: DNS ...
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8 votes
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Why is DNS an application layer protocol?

DNS is a application layer protocol, because DNS query and answer is the application level communications. Application layer only understand the query and answer section in the DNS packet. so ...
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7 votes
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Cisco ASA VPN with split-dns on a Windows VPN client

Experiment There is a lot of conflicting information about what actually happens on a Windows client when using split-dns. So much that I decided to gather some evidence and see where it points. I ...
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6 votes
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Why do some AAAA records behave strangely on existing A records?

I actually found what I was looking for in RFC4074: Suppose that an authoritative server has an A RR but has no AAAA RR for a host name. Then, the server should return a response to a query for an ...
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6 votes
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What is IP-over-DNS tunnelling?

Ron is right with his comment. IP-over-DNS tunneling (or more common name DNS tunneling) is a kind of attack, that allows to bypass usual network protection and send/receive data over DNS protocol, ...
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  • 334
6 votes

Why is DNS an application layer protocol?

Protocols at the Physical, Data-Link, Network, or Transport layers do not use names. Only applications need to use names, so DNS is an application-layer protocol because it allows the application to ...
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6 votes

Can I see what happens when I run a DNS query?

As others have already answered, most usually a host sends a recursive query to a nominated resolver, often a local server or router, often belonging to an ISP or Google's well-known (distributed) 8.8....
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5 votes
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Choosing between BGP (AS Number) and Dynamic DNS

DynDNS Using DynDNS is not a viable solution for your usecase since its primary use case is mapping a dynamic ip address to a dns record. If you have two Upstreams with different ip subnets you would ...
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  • 767
5 votes
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Where is dns root server located?

Most of the information can be found here: http://www.root-servers.org/ There are several in different regions of the world, see link above for map There are 12 companies that operate them, they are ...
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  • 566
5 votes
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Why does a NS record need a domain name, not an IP address?

MX, CNAME, PTR, and NS records point to hostnames. A records point to IP addresses. Putting an IP address in an NS record is a pretty common DNS misconfiguration. One reason is that you might have ...
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  • 603
5 votes

It's not showing the DNS why it is called reverse IP lookup?

Reverse DNS is a term for looking up the DNS PTR record for an IP address - essentially resolving it 'backwards' to a host name (in contrast to 'forward' resolving a host name to an IP address using ...
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5 votes
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What are some high-traffic websites that operate with a global anycast IP address?

A couple of examples are: api.twitter.com one.one.one.one dns.google There are always exceptions however - you'll notice that within China, the IP for say api.twitter.com is different for reasons ...
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5 votes

What's the meaning of requests in Load-balancer?

That seems to use the term 'request' both for DNS queries and for HTTP requests, which makes it a bit confusing. Most load balancers however are able to balance all kinds of application protocols, ...
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4 votes

How are packets routed based on IP and how are those routes acquired?

Routers learn about routes in three ways: Directly connected networks Manually configured static routes Dynamically through routing protocols A router, receiving a packet on an interface will look ...
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4 votes
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Nameserver availability within single ASN

Multi-ASN in this case is more of a proxy for a high degree of network resilience. The basic idea is that primary and secondary servers should be deployed in such a way that the loss of even multiple ...
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4 votes

Why is DNS an application layer protocol?

I think that DNS is an application layer protocol because if for example i want to create a TCP connection i need the destination ip address in layer 4, Am i correct? IP is a layer 3 protocol. ...
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  • 1,437
4 votes

Can I see what happens when I run a DNS query?

A normal DNS client just queries the (DHCP or statically) assigned DNS servers. Only DNS servers usually query root servers, doing a recursive query. You can use a packet capture of your choice and ...
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4 votes
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If you have multiple domains pointing to the same IP address, can you see which domain a packet was sent to?

Application-layer protocols such as HTTP generally have this capability. At the network layer, no, you can't tell.
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4 votes
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Why DNS services Like google public DNS and Cloudflare 1.1.1.1 has ipv6 versions?

The plan for IPv6 is to ultimately replace IPv4 in entirety. In the long run, it doesn't make sense to run two full stacks in parallel. Also, some providers serve their clients using IPv4 private ...
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  • 69.5k
3 votes

DNS analytics solutions?

Study BIND's logging clause.[1][2][3] Here's what I've used for decades: logging { channel syslog_debug { syslog daemon; severity debug; print-...
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3 votes
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Only DNS filter guest wireless network, but not main wireless network running through same port on switch

I assume you are using OpenDNS' web filtering functionality here, and it looks like that essentially involves using their DNS servers to handle lookups, rather than your own. You could define two ...
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3 votes

How do you check glue records if your ISP blocks access to the root servers?

Change your ISP. Blocking access to root DNS servers with "DoS prevention" is not something a serious ISP would practice (unless you live in a country with government regulations in place). ...
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3 votes

Connecting to remote device via hostname that gets its IP from DHCP

If your DHCP and DNS servers both implement DDNS (that's Dynamic [updates] to DNS, I know ISC's Open Source servers do this, and I'm sure there are several others), you can have the DHCP server update ...
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  • 346
3 votes

How WANs work and why it is it bad to run DNS and DHCP on a router?

WAN is a very subjective term. Routers have interfaces. Some types of router interfaces are more likely to be used as or called WAN interfaces. For example, PPP, HDLC, Frame relay, etc. are rarely ...
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3 votes
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Host IPv6-only website and allow access to IPv4-only clients

IPv4 and IPv6 are separate protocols. So if you want IPv4 only clients to be able to access your IPv6 only server you will need some kind of gateway/proxy service that can provide an IPv4 address to ...
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  • 11.6k
3 votes
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Router decision making w.r.t web browsers

You're mixing up various layers of the Internet Protocol Suite (or OSI model if you like). Routers do not interact with browers directly. Routers interact with hosts, which have IP addresses. As far ...
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3 votes
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Who generates all the DNS requests when I plug my public IP router to the network?

Many (really, really many) bots scan all Internet public IP all time, and try to exploit any weakness found in many way. Specifically, DNS is often used to perform DDOS attack by amplification, see ...
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3 votes
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Why only 13 adresses for the DNS root zone

"Each IPv4 address" meaning "each IPv4 DNS root server entry". The article is quite clear on this. 512 bytes of (minimum) UDP payload divided by 32 bytes equals 16. They left 96 bytes for future ...
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