I have the need to do my own DNS queries. However there does not appear to be a way to get the DNS servers address from the device.
IPAddressCollection dnsAddresses = ipProperties.DnsAddresses;
This always returns 0 DNS servers but yet it works fine in the simulator. Is there any kind of workaround to get this working?
Thanks
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I am trying to switch my dynamic DNS from IPv4 to IPv6, but I am encountering a strange issue. The device is accessible via its raw IPv6 address, but whatever dynamic DNS server I use, it always results in an IP address not found issue. The IPv4 one works fine though. The server is also correctly configured, otherwise the raw address would not work.
What is even stranger is that services like http://ipv6-test.com seem to be able to verify that IPv6 functionality exists and also which web server I use. They also list the corresponding name servers.
I tried the dynamic DNS services of spdyn, dynv6, and ddnss. I also tried noip, but it seems they only support IPv4 for free. (My IPv4 one is with noip.)
Does anybody have some advice? I'm thankful for any help!
Most probably your network is not supporting IPv6.
For example, I've a server hosted at my home with 2 NICs for redundancy obviously.
NIC1 has been assigned with the public IP 103.204.82.22 from ISP1
NIC2 has been assigned with the public IP 144.110.12.64 from ISP2
I can access the server with both IP as usual.
Now, I have a domain acme.com. I've created a subdomain server.acme.com. I want to point server.acme.com to both the IPs so that in case one ISP fails to provide connectivity my server still remains online with the other one.
I've already tried with A and CNAME records. But it isn't working. It's working with A record if I use only one IP for the subdomain.
Can anyone tell me what and how can I point both the IPs to the single subdomain?
Thanks in advance
What you are describing is called DNS round robin, but that won't give you your expected outcome.
Anything you do with DNS if one ISP connection is down, traffic will still go there.
You may have your terminology mixed up a little to start with.
in this case, I suspect you really mean that server.acme.com is a host record, rather than a subdomain. (A subdomain would mean that the server address would be at servername.server.acme.com)
If you create an A record, and put both IP addresses in, and keep the TTL (time to live) short, then when a client wants to contact your machine it will randomly pick one of the addresses. If that address is unavailable, it will move on to the next. If that address stops working, it will keep trying it for the 'TTL' time.
Presuming that the IP addresses don't change, which would be a different problem altogether, then this provide basic load balancing and failover to both connections.
Amazon provide a more advanced type of DNS, that will actively monitor your connections and only provide responses that are live. - https://docs.aws.amazon.com/Route53/latest/DeveloperGuide/routing-policy.html
In this moment, I am learning how the DNS and domains resolutions work and I have a question.
Let's take a.test.com for example.
As I understand it, first of all, the intermediary ISP DNS server is called. If it has the domain IP in cache, it returns it. Otherwise, it does consecutively these following tasks :
It calls a root DNS server which returns a com DNS server IP
It calls that top level DNS server which returns the test.com DNS server IP
It calls that DNS server to finally get a.test.com's IP
Is it correct ?
And now what does it happen when we resolve a.b.c.test.com ?
Does it call another DNS server or does the c.test.com's DNS server contain the a.b.c.test.com's IP ?
Thanks
Yes, you are pretty much correct. Nothing different will happen in next steps: c.test.com will respond with a referral to more authoritative server (the one for b.c.test.com), or if itself is authoritative then it will respond with an answer.
This is not a C# question. This has to do more with our servers. Basically we've been noticing that another DNS address is resolving to our server's address, example.
Our DNS: www.bob.com
The other mysterious DNS that resolves to our IP: thing.blah8.com
This is actually a rather serious issue because some how this random DNS is being picked up by google and people are reaching our website through this address. So anyone have any ideas where this second DNS address is coming from? Anyone seen this strange behavior before? I'm guessing it might be the name of the box of our webhost.
Any hints or tips of where to look would be great. As a note, we've already checked our DNS server and there is no obvious clue as to where that address is coming from.
You can try contacting their technical domain contact (get it through a WHOIS request) and let them know their DNS is wrong. There's nothing you could forcefully do to stop them, outside of catching this hostname request with your web server and serving those visitors a different page. Some might say traffic is traffic, but I assume you don't agree. :)
It doesn't have anything to do with your servers, it's the remote sites DNS zone that is configured with your IP address. You couldn't make that happen.
Our user interface is communicating with another application on a different machine, often connecting using domain names.
On our network, when IPv6 is installed, DNS name resolution works great, all machines can be pinged and contacted fine.
When IPv6 is uninstalled, pinging the same DNS names returns an IP address on some distant subnet (24.28.193.9; local subnet is 192.168.1.1); our application is then unable to communicate. When IPv6 is reinstalled, the DNS resolution corrects itself.
Even without IPv6 when ping is not working, I can still browse other machines using Windows Explorer by entering \\\\MACHINE_NAME\\. I'm not sure why the name resolution seems to work here. We are working in the Windows XP SP2 environment.
The IPs of the machines can be pinged successfully. It is only the DNS names that do not resolve properly.
I looked for the address of our DNS server. All of our computers are pointing at the network gateway, which is a wireless router. The router has the same DNS server address listed when IPv6 is installed as it does when it isn't installed.
The strangest thing is that I just discovered that it does not matter what DNS name I ping. All pings to DNS names return the same address: "24.28.193.9".
I tried flushing the DNS Resolver Cache and registering DNS on the target machine and the source machine. All to no avail. The only DNS name that I can ping is the name of the current machine.
Any thoughts as to why our software can't communicate without IPv6 installed?
UPDATE:
OK, I've done a little more research now.
I looked for the address of our DNS server. All of our computers are pointing at the network gateway, which is a wireless router. The router has the same DNS server address listed when IPv6 is installed as it does when it isn't installed.
The strangest thing is that I just discovered that it does not matter what DNS name I ping. All pings to DNS names return the same address: "24.28.193.9".
I tried flushing the DNS Resolver Cache and registering DNS on the target machine and the source machine. All to no avail. The only DNS name that I can ping is the name of the current machine.
Any other suggestions? Thanks so much for your help.
You've got multiple things going on here
DNS Name resolution
Windows Name resolution
IP-IP ICMP communication
You've written your question as if there's a problem with #3, but everything you describe points to the problem actually being with #1. If you take resolution out of the question, can you ping the correct IPs with our without IPv6 installed?
It sounds like maybe you have an IPv6 name server installed that has correct information and the IPv4 name server is incorrect? Are you receiving name servers via DHCP or hard coding? What are the IPs of the name servers you are using when IPv6 is installed and when it isn't?
I know this is a late answer, but in case someone else has the same problem, the key is the IP address, "24.28.193.9". A quick Google search reveals it seems to be related to your ISP completely breaking the DNS protocol by returning a fixed IP address for all non-existent domain names (the correct answer would be NXDOMAIN). Your network gateway is most probably just forwarding your queries to your ISP's name servers.
Your systems are relying on the correct operation of the DNS protocol. They are expecting a NXDOMAIN answer before querying the name via other methods (most probably NetBIOS name resolution). Since the DNS server is completely broken and returning an incorrect answer, the correct address is never looked up.
The reason installing or uninstalling IPv6 changes the situation is most probably because something related to it is changing the name resolution order (to look up using other methods before trying DNS). So, a workaround would be to change the name resolution order yourself.
The real fix would be to either change to a better ISP (one which does not break established protocols) or run your own DNS server (which is what I started doing on all systems I administer ever since VeriSign pulled a similar stunt; theirs was even worse in that changing ISPs made no difference at all).
References:
Warning: Road Runner DNS says nonexistent domains exist