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Why 2 NS 2 Different IP?
| Posted by promocode, 05-02-2014, 01:10 PM |
| Guys... I have a doubt here, hope can get clearer picture.
1st senario
For reseller/shared hosting, usually we will have different IP for both NS.
ns1.domain.com xxx.xxx.xxx.xxx
ns2.domain.com yyy.yyy.yyy.yyy
Understand that both NS pointing to the same server.
We use both NS because of redundancy (correct me if I am wrong) if one IP goes down, another still pointing to the same server.
But what i understand, IP is hardly down.
2nd Senario
While if I sign up VPS, mostly service provider provide 1 IP, and understand that both of my NS are pointing to the same IP
ns1.domain.com xxx.xxx.xxx.xxx
ns2.domain.com xxx.xxx.xxx.xxx
So over here, my curiousity is, if IP hardly goes down, usually server goes down, what is the different by using 1 IP or 2 IP (for name server 1 and 2)?
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| Posted by neil@ukwebhosting, 05-02-2014, 01:27 PM |
| If the IPs are on the same server then nothing at all
If the different IPs are on different servers and probably set up as part of a DNS cluster then the advantages are usually if the server goes down the websites DNS will resolve quicker, when back up email is not bounced immediately and can move accounts across server in the DNS cluster with no propagation time
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| Posted by OvcaX, 05-02-2014, 01:27 PM |
| Helo,
It's not 2 IP, its 2 separate NS servers
This is to have redundancy on DNS servers
Best,
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| Posted by Johnny Cache, 05-02-2014, 01:54 PM |
| neil@ukwebhosting's statement remains accurate. To achieve some actual level of redundancy for DNS, you would need something more on the lines of a cross-datacenter DNS cluster setup (e.g., small VPS running CP DNSONLY). Otherwise, you could have 123.123.123.123 and 234.234.234.234 but as long as they're both programmed on the same physical server, you're still at a single point-of-failure. Meaning that if BIND crashed, your sites are going with it. Does that clarify a bit more?
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| Posted by promocode, 05-02-2014, 09:39 PM |
| I do hear before separate server such as clustering. But I wonder is this the best practice for reseller provider?
most of the share hosting/reseller hosting use 2 server to run cluster? Sound like costly to the provider.
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| Posted by WestNIC, 05-03-2014, 01:34 AM |
| Redundant DNS cost close to nothing. You can get two small VPS for 5 bucks each then load cPanel DNS-only clusters (no license fees). This would work perfectly for few thousand websites.
Hosting DNS on the same server is a bad idea.
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| Posted by promocode, 05-03-2014, 01:57 AM |
| Hosting redundant DNS sound new to me, would you guys mind to fill me a clear picture? I never know the actual setup on back end.
Is this mean:
actual server IP is xxx.xxx.xxx.xxx
We set the dns
ns1.domain.com xxx.xxx.xxx.xxx
ns2.domain.com yyy.yyy.yyy.yyy
while ns2.domain.com ns is actually hosted in the small vps you mention (which this small vps IP is yyy.yyy.yyy.yyy), and within this small vps, we point it again to actual server xxx.xxx.xxx.xxx ?
Correct me if my imagination is wrong.
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| Posted by WestNIC, 05-03-2014, 03:01 AM |
| Please check this out. Fully redundant DNS:
Actual server IP: xxx.xxx.xxx.xxx
VPS1 (primary DNS cluster): yyy.yyy.yyy.yyy
VPS2 (secondary DNS cluster): zzz.zzz.zzz.zzz
So when you add hosting account on actual cPanel server, local DNS zone will be distributed across clusters (synchronized).
If you host few hundred websites, you may setup primary on the same server and secondary on cluster. This would cost even less:
Actual server IP: xxx.xxx.xxx.xxx
Actual server (primary DNS, same server but different IP): yyy.yyy.yyy.yyy
VPS1 (secondary DNS cluster): zzz.zzz.zzz.zzz
You still have to obtain two dedicated IPs for name servers. Those IPs must be in different class C subnets, for example, ns1 > 192.168.1.1 and ns2 > 192.168.2.2
You should setup secondary DNS cluster in different data center for extra redundancy. To run DNS cluster you need to load OS first (most use Centos 6.x) and then load cPanel DNS-only via VPS shell.
cPanel DNS only normally installs in 30-40 minutes. Configuration process (including firewall install/configuration) takes another 15-20 minutes.
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| Posted by neil@ukwebhosting, 05-03-2014, 06:54 AM |
| I did once encounter the unfortunate situation of both NS going down at the same time in two different data centres.
Usually on the hosting server I turn bind off as with a DNS cluster it is redundant, but I wonder what the advantages are of actually making ns3 the shared IP?
So if the 1st paragraphs issue ever happens again they could resolve from the servers IP?
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| Posted by neil@ukwebhosting, 05-03-2014, 08:13 AM |
| The advantage to a reseller is if they have lots of servers and one server is facing a lot of problems they can transfer the accounts to a new server, update the dns in the cluster and server the clients accounts from the new server with no downtime while propagation occurs and also without requiring the clients to update their nameservers.
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| Posted by WestNIC, 05-03-2014, 05:26 PM |
| It happens..
RFC2182 section 5 ("How many secondaries?" https://tools.ietf.org/html/rfc2182 ) recommends at least 3 name servers; two of them should be spreaded geographically. However, cPanel GUI supports only 4.
It does make sense to make ns3 on local hosting server. If two clusters get disconnected for some reason, DNS zone will be fetched from ns3 which is on the same hosting server. However, it may be difficult to manage ns3 if you planning to add more servers. Cluster (ns3) won't be reliable.
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| Posted by neil@ukwebhosting, 05-03-2014, 05:36 PM |
| Yeah, I've just realised it wouldn't work, or wouldn't be easy
I have 2 nameservers in a DNS cluster, these are serving 3 hosting servers, so, I'd have to make
ns3 - to server 1 ip
ns4 - to server 2 ip
ns5 - to server 3 ip
All getting a bit messy and have no idea what the sync would be like, or do you mean make your most powerful hosting server the third NS in the cluster only to serve all 3 hosting servers?
Interesting ideas but I prefer things clean and logical.
Sorry if this is a hijack, just mussing ideas on the original question.
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| Posted by PremiumHost, 05-04-2014, 10:13 PM |
| If you use cpanel dns cluster, dns change should be pushed to all servers in cluster within seconds.
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| Posted by SupportGuide, 05-05-2014, 11:16 PM |
| It is supposed to be two different name servers, but many hosts cheat and give you one name server, and give you two IP addresses to make it appear there are two name servers.
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