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Questions tagged [dns]

This tag should only be used when it's about configuration of DNS on an on topic network device. Any general DNS service related questions are off topic.

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where is the local resolver? [closed]

I'm looking into dns cache poisoning and I was confused as to where the local resolver was located. From what I understand the local resolver is located in a DNS server where we perform lookups when ...
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3 answers
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What if I run tracert command while there is no connection to the DNS server?

What happens if I run the tracert x.x.x.x command while there is no connection to the DNS server?
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1 answer
106 views

Configure AAA on a router - Extended ACLs

How do I write a named extended ACL which will allow for traffic between a DNS from a LAN (IP address) to a DNS server at (IP address), ping from a host PC (IP address) to any destination and allow ...
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1 answer
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How to force routing to https website without the IP

I am attempting to limit a group of Chromebooks to access one particular site for student testing. The issue is that the website is secure but the ssl cert is attached to the url not the ip. The ip of ...
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2 answers
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Do domains frequently change their IP addresses

I have the domain of some organization that requests my site too much. I want to restrict their access - but how? We only have the domain of the requester sfasu.edu . The QA of our team is using tool ...
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Cisco DHCP using dynamic updates

I would like to use a configuration on a Cisco router that allows for clients to resolve the names of other clients without the use of mDNS. I have following configuration: roTST01#show running-config ...
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2 answers
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Packet Tracer - PING from CLI of router to website

I am currently sending a PING from a Router2 of the Network shown bellow. By using the CLI commands I'm trying to do it in 2 different ways: PING + IP 192.168.1.9. As a result, it succeeds. PING + ...
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1 vote
2 answers
57 views

How do machines setup a route in a network?

So I have been reading a bit about networking, and I am a bit confused about what exactly happens after domain name resolutions. Lets say I do a get request to "some.website.com". First, my ...
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1 answer
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Why can't I access Whitehouse.Gov with the IP address or the Aliases? [closed]

I'm studying the basics of networking at the moment, and I was testing out what I had learned when I discovered that I could not access WhiteHouse.gov via the IP address. After using dig on WhiteHouse....
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1 answer
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What is the significance of configure TTL value while creating A record and AAAA Record in External DNS [closed]

Is Time to live (TTL) value has any impact on DNS querry . Because in our external DNS we generally set TTL value to 1 hours and some times 5 minutes while creating A records and AAAA records in ...
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1 answer
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Why DNS services Like google public DNS and Cloudflare 1.1.1.1 has ipv6 versions?

I understand the need for ipv6 as we ran out of ipv4 but dns resolvers like google and cloudflare already have ipv4 addresses for resolving dns and i don't see compatibility as a reason either because ...
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1 answer
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How is traceroute able to display hostnames?

When performing a traceroute, what function on the ISP gateway is advertising the hostname? When we traceroute to Google.com for instance; Tracing route to google.com [216.58.213.14] over a maximum of ...
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2 answers
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What's the meaning of requests in Load-balancer?

When I read thisarticle: there is a term: Load-balancer is the piece of hardware that listens on a particular IP address and forwards the requests to other servers. Major sites will typically use ...
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1 answer
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DNS request on google.com. with QTYPE = 0xff returns no entries [closed]

Ive written my own DNS request client but I'm having some interesting behavior. If I send the request with the QTYPE section = 0xff, I get a valid response however with no entries. My Request: 0x70 ...
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1 answer
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How do I know when an AAAA record is required? [closed]

I'm trying to wrap my head around DNS. My biggest issue right now is understanding when an AAAA record is required. Recently, I was asked by a colleague to point a subdomain from Server A to Server B....
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1 answer
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Will DNS TTL impact Browser’s HTTP Cache? [closed]

Browsers are known to cache HTTP resources to save bandwidth and improve performance. I’m not 100% sure about how HTTP cache works in web browsers but I can see sometimes that an object with “cache-...
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1 answer
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What is the purpose of Cisco's `ip domain round-robin` feature?

While configuring one of Cisco's routers and reading documentation I've found an interesting feature: ip domain round-robin. Documentation says, that this options makes dns server rotate entries ...
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2 answers
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Can Cisco Config cause Unidentified Network

I have a Cisco C9300-24P layer 2 switch with a dozen computers and 2 servers on the same VLAN, all statically set with no default gateway as there is no router and all offline from the internet. The ...
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2 answers
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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? [closed]

If you have multiple domains pointing to the same IP address, can you see which domain a packet was sent to?
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2 answers
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Best way to make a network failsafe?

I have a Debian based machine with 2 completely different network interfaces from 2 different ISPs acting as a backup for my server connection. These have two different IPs (Let's say IP1 and ...
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2 answers
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Why can i ping domain from Pfsense diagnostics but not from my desktop?

I'm setting up Pfsense to replace our existing firewall with. Currently the setup is pretty straight forward. I have internet connected to my wan port connected a switch to the lan port connected ...
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If a server has both IPv4 and IPv6 addresses, how does the DNS determine which to return? See the following example [closed]

These Pings were done at different times of the same day: C:\Users\LPress>ping www.ucla.edu Pinging gateway.lb.it.ucla.edu [164.67.228.152] with 32 bytes of data: C:\Users\LPress>ping www.ucla.edu ...
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2 answers
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How can I use 1 static public IP address for multiple private networks in totally different physcical locations?

So, I know that DNS is important in the running of CDN services. DNS allows the routing client traffic to the physically nearest CDN server. Question is, how can I do the same thing without any DNS ...
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1 answer
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Able to ping Domain internal address on home network, why? [closed]

I have a strange issue, I am able to ping my company's internal address (ex: hq.mycomapny.com) when I am on my Home network (WI-FI or Enthernet) and NOT connected to the VPN. When I do a ping on the ...
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2 votes
1 answer
587 views

Cisco IOS: DNS Servers via DHCP

Simple question: I have following switch configuration: interface Vlan1 ip address dhcp end ip domain-lookup I receive and IP and DNS servers along with it from our DHCP server. At least Windows ...
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1 answer
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What special reserved domain could I use for virtual organization private network? [closed]

Suppose we have a inner-facing network that spans several geographical jurisdiction - this network can only accessed from our offices with special HSM installed, and we want to enable domain-name-...
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2 votes
2 answers
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What are some high-traffic websites that operate with a global anycast IP address?

I've been trying to find an example of an anycast IP address used by a hugely popular service or a website. According to my queries at https://www.whatsmydns.net/ , none of the large sites that are ...
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1 vote
1 answer
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DNS expire-entry-timer has negative affect on ASA using FQDN ACL

I have a Cisco ASA using FQDN egress ACLs for a host that changes IP addresses every 10 mins (Apple APNS IP address pool). As soon as the TTL expires for the addresses, my internal server requests a ...
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LAN to WAN IPv4 address mapped to LAN server through NAT Rules or other

I need to set a rule that allows me to connect BOTH from OUTSIDE the LAN (from the "internet" to the Internal server at IPv4 address 10.64.0.50 via port 22, by running ssh://1.2.3.4 -p 22; AND From ...
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2 votes
1 answer
520 views

How does a DNS response reach a client behind a NAT?

How does a DNS response reach a client behind a NAT? I'm talking about DNS queries using UDP for transport with a server that is not in the same network as the client. Does the NAT correlate the ...
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1 vote
1 answer
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Why does www DNS record propagate faster than @? [closed]

I've recently had to move a DNS ownership from one DigitalOcean account to another. During this process I've noticed that the www A DNS record propagates a lot faster than the @ A DNS record. Why ...
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1 answer
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Dynamic DNS and VPN [closed]

I have a few PCs/services that I want to access remotely, which are inside a VPN and gets assigned local IP addresses using DHCP. How can I setup dynamic DNS to access the PCs on their internal VPN ...
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-1 votes
3 answers
376 views

ACL for DNS clarification

I do not understand why the second ACL is needed if all I want is to ensure all networks use a certain DNS server (for example 192.0.2.1) access-list 112 permit udp any host 192.0.2.1 eq domain ...
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1 vote
0 answers
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DNS not resolving through VPN [closed]

Looking for some help with our Office's VPN that I can't seem to solve... I am trying to remote desktop to the Work PC from Home PC via the DC ASA 5506-x VPN. I can only connect to the Work PC with ...
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1 vote
0 answers
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Cisco IP SLA HTTP request with frontdoor VRF

I am trying to use a IP SLA for HTTP on my Cisco ISR 4321 router to check if a website is reachable. The challenge is that I need to do that in a frontdoor VRF. I have configured ip name-server vrf ...
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0 votes
1 answer
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How is a lost DNS query handled [closed]

If a DNS query gets lost along the way to its destination, is nothing done about it? In my networking class, my lecturer said that DNS runs on UDP. I verified this in Wireshark by doing nslookup for a ...
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2 votes
4 answers
2k views

connect a cisco router to the internet through a cable modem

The router gets an External IP address via DHCP from the Cable modem Clients inside the network get an IP address from Router's DHCP server I can ping that the external IP address from a client inside ...
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1 vote
1 answer
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How do I find the IP of the DNS server that respond for a specific domain name?

So as the title says I want to get the IP of the DNS server that respond when I'm trying to reach a specific domain, using bash commands. If I understood it right, when I'm trying to reach www....
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1 vote
1 answer
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Quanta switch not resolving addresses

I've got this brand new Quanta T3048. I've configured the VLANs we need but it came to my attention that the switch won't resolve any address even though I've set it (according to the configuration ...
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2 answers
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It's not showing the DNS why it is called reverse IP lookup? [closed]

I have searched a lot but I didn't get the reason that even after giving the IP address it never shows the DNS. If it doesn't give the DNS then why it is said to be reverse IP lookup?
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2 answers
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Access internal webserver with domainname points to external IP

We have a webserver on our LAN. Externally, we can use the public domainname (let's say business.com) to access the website. Internally, we need to use the local IP. We also want to use the public ...
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1 vote
0 answers
224 views

Different DNS resolution for same domain name [closed]

I am getting different DNS resolution for www.google.com. When I am using Google Public DNS i.e 8.8.8.8 then by using nslookup then it is giving IP address of Non-authoritative answer: Name: www....
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1 vote
1 answer
1k views

Can I ping a specific site without DNS server information? [closed]

If I clear DNS cache and remove DNS server information, how can I ping to a specific site?
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1 vote
2 answers
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How to force users on my LAN to use a specific DNS server using ARP poisoning?

I'm attempting to force all hosts on my LAN to use a specific DNS server to filter certain material, however I'm running into problems. I've had problems in the past trying to configure my router's ...
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1 vote
1 answer
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TZ205W DNS Issue

I have a firewall that is setup but need to have all users inside the network to use a preset dns server. While I know that I can set up this in the DHCP it does not stop a user from changing it in ...
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2 answers
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How can a public DNS server know the hostname of a machine on a private network [closed]

Example: a home LAN a simple SOHO router (both DHCP and DNS server at 192.168.1.1) 2 client machines (192.168.1.2 and 192.168.1.3) Is it possible for the Google public DNS server located at 8.8.8.8 (...
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0 votes
1 answer
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Iterative queries of a default DNS server

I have just started to study networks and I have a confusion about what happens when a default DNS server does iterative queries to other DNS servers to resolve a name in an IP address. I am very ...
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3 votes
4 answers
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Can I see what happens when I run a DNS query?

My understanding is that when my computer wants to resolve a host name, it will ask the DHCP-assigned DNS servers first. If those don’t know, it goes and asks the ‘root servers’ who then defer to ...
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0 votes
1 answer
61 views

SRV Record for Service X [closed]

I've got a quite common question, which I can't find an answer for. Is it possible to create a SRV Record for any possible service I'm running? For example: I want webinterface.example.com to ...
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1 answer
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Is it possible to convert a public IP and port to a DNS? [closed]

Must be said, I'm a complete ignorant on these matters. Is there a way or service so I can take and IP address and its port and make it a DNS? Is it possible or am I doomed?. Thank you.
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