I need to know about child nameserver, What is it and for what purpose can we use that ?
I have seen an option in whois.com about child name server which has to be pointed out to an ip address, I have tried to use as an subdomain, but I can use subdomain by another way, so basically what is use of that actually ?
Quoting from a source I found using Google:
"Child Name Servers are private labelled name servers which are registered with domain registry under your own domain name.
eg. ns1.domainname.com, ns2.domainname.com
Child Name Servers needs to be registered with registry and also it's A record needs to be pointed to IP address of DNS Server before they can be used as name servers with other domain names. Child Name Servers can be only registered by owner of the primary domain name."
You could use them for a number of reasons; e.g.
If the parent nameserver is run by a DNS provider, the child nameserver could allow you to host the names in the subdomain yourself ... and update them without relying on the DNS provider's (possibly clunky) APIs.
Within a large organization it could allow the management of different subdomains to be done by different groups.
You might do it if you wanted a subdomain to contain dynamic names.
I have seen an option in whois.com ...
I think you might be confused about the purpose of the WHOIS service. It is purely for documenting which people (notionally) control which domains. To implement a child domainserver, you just need an A record in the parent domainserver that points to the child.
Related
If I am right the nameServerSet could give me the option to specify the DNS servers to handle request for a domain, this could be useful if I want to use my own domains like for doing white label.
From the docs: nameServerSet
nameServerSet Optionally specifies the NameServerSet for this
ManagedZone. A NameServerSet is a set of DNS name servers that all
host the same ManagedZones. Most users will leave this field unset.
But what are the posible "string" values to use?
A web designer friend of mine is moving a customer of hers to a new hosting provider but she wanted me to look at their email setup to make sure that nothing she was doing would affect their email. I did an assortment of MX record and dns record lookups and to me there seems to be something really strange with their mail setup. For example, there are two mx records where I'm used to seeing one (domain names and ip addresses are dummy's just to be safe): Pref: 10 hostname: mx.name.net ip address: 111.222.555.333 and the second Pref: 20 hostname: mx.ct.diffname.net ip address: 111.222.444.222 and neither "name" nor "diffnam" is their domain name. Then the dns entry for mail.theirdomain.net points to an address that's different from either the two addresses pointed to by the mx record.
I haven't setup a mail server in a while but I checked the last one I did and in the mx record the hostname was mail.domainname.org (and there was only one entry) and the address in the mx record was the same as the address in the mail.domainname.org dns entry.
I could understand if there were two MX records for either load balancing or fail-over in case the main server went down but the setup seems strange and the fact that the mail.domainname.com dns entry doesn't point to the same address as the mx record makes me think something is setup wrong in their email system. Does anyone have some insight into this?
mail.domainname.com has nothing to do with MX or SMTP; it's just a normal domain name.
It typically points to an HTTP server that serves webmail, which may or may not be the same as the SMTP server.
The point of having multiple MX records is in case one of them goes down.
In a DNS zone file, there are different entries that denote the type of service for which a canonical may be directed. One of these is the MX record which determines where services look for email SMTP access. The primary record is called the A record, which usually directs to the IP address(s) for web services and the primary domain.
Hope this helps!
I found in DNS setting, there is a period after the record. I am wondering what's the reason for this?
For example test.test.com.
The 'dot' is the root of the DNS heirarchy and, on some systems, if you don't use it the DNS server thinks it's a record in the current zone and will append it, rather than treating it as an FQDN (Fully Qualified Domain Name)
G
Just want to see if I understand this correctly.
CNAME record specifies an alias, in the following form:
alias CNAME canonical-domain
Which means if something is trying to look up alias, it will find the CNAME record and start searching for canonical-domain instead.
A record directly maps a host to an IP
host A IP-addr
So if I have 2 domains eventually pointing to the same IP addr, one is a canonical domain and another is an alias domain, I would use an A record for the canonical domain->IP mapping, and a CNAME record for the alias->canonical mapping.
Why can't I just use 2 A records, one being canonical->IP mapping and the other being alias->IP mapping? Is it so that you only have to update the IP once if you ever need to change it? (Analogy would be CNAME is a softlink and A record is a file in a filesystem)
Why can't I just use 2 A records, one being canonical->IP mapping and
the other being alias->IP mapping?
You can - that's perfectly normal.
Is it so that you only have to update the IP once if you ever need to
change it?
Yes, that's right.
A common configuration is to have the canonical name being the server's real hostname, and then CNAME records for the sites hosted on that server pointing at that.
Note that you can't have a CNAME for a bare domain name (e.g. stackoverflow.com) . A CNAME record can't coexist with the NS and SOA records that are expected to exist at the apex of a zone.
(Analogy would be CNAME is a softlink and A record is a file in a
filesystem)
That's not an analogy I'd use.
Below is a sample invoking of getaddrinfo()
status = getaddrinfo("www.example.net","1234", &hints, &server_info);
After that, the server_info will point to a linked list with all kinds of address information.
I have the following questions:
Since I have clearly specified the host name and port number, the only address infos I can think of are IPv4 and IPv6 addresses. So, the length of the linked list should be 2. Is there any other kind of address info besides them?
Thanks.
The name could resolve to more than one IPv4 or IPv6 address, there is nothing to say that only one IPv4 address will be returned, for example (try it with "www.google.com" for example, you'll likely get more than one IPv4 address).
But in any case, I think the basic premise of your question is wrong. Even if there was no possibility to return more than one IPv4 and one IPv6 address today, the function is documented to return an arbitrarily-long linked list of addrinfo objects. Therefore, even if your code worked today in every situation, there is no guarantee that it would continue to work tomorrow. If the function is documented to return an arbitrarily-long linked list, then you need to be able to handle that.
You want to disconnect the physical configuration of machines with names in your mind. DNS merely maps a name to a set of addresses. A lot of hosts will only have one interface. Many hosts will have multiple (called multi-homing). DNS doesn't care about what the configuration of the machine or machines that the addresses it maps a name to is. As simple examples often a server will have interfaces on multiple networks with different addresses that will all map to the same name. Sometimes when collapsing services from different machines onto one different names will map to the same address. So don't assume any sort of 1:1 mapping between names and machines much less interfaces.