sara2000
asked on
Multiple A record for a single IP
We have a server with multiple A records pointing to one IP. The server names srv1 and mydomain.
the reverse DNS entry is pointing to srv1. I installed a Linux server. The Linux server is resolving srv1 when I run nslook up, but not mydomain. It is strange that Windows PC are resolving both names.
How do I make the Linux to resolve both server's name?
the reverse DNS entry is pointing to srv1. I installed a Linux server. The Linux server is resolving srv1 when I run nslook up, but not mydomain. It is strange that Windows PC are resolving both names.
How do I make the Linux to resolve both server's name?
David Johnson, CD
use a CNAME record for additional names
ASKER
I have to find the reason why it does not resolve when we use multiple names for same IP. Not sure why the developer does not want to use the CNAME? maybe He wants a single ip for HA etc.
if you have multiple A records it will round robin them
If you're running a Windows DNS server, have you enabled round robin DNS? Under the DNS server properties in the DNS console, make sure that "Enable round robin" is ticked.
DNS round robin does != HA. DNS is "stupid" in that it will send you to the host whether it is up or down. It has no built-in health check.
maybe He wants a single ip for HA etc.
DNS round robin does != HA. DNS is "stupid" in that it will send you to the host whether it is up or down. It has no built-in health check.
This all needs to be clarified.
Round robin only comes into effect if you have multiple A records with the same name pointing to different IPs (not multiple A records with different names pointing to the same IP).
If you have multiple A records with the same name pointing to different IPs, the record that gets returned first can also be influenced by subnet prioritization.
When you're running the nslookup tests, what are you looking at? The A records or the PTR records? Have you tried using Dig?
Round robin only comes into effect if you have multiple A records with the same name pointing to different IPs (not multiple A records with different names pointing to the same IP).
If you have multiple A records with the same name pointing to different IPs, the record that gets returned first can also be influenced by subnet prioritization.
When you're running the nslookup tests, what are you looking at? The A records or the PTR records? Have you tried using Dig?
You can verify DNS issues using the dig tool on linux.
(part of bind-tools in most distributions).
forward lookup with:
dig srv1.yourdomain.whatever
dig mydomain.yourdomain.whatev
This should show the A records.
if you do a revers lookup
dig -x the.ip.address.ofthesystem
This should show the PTR records.
there is a requirement from DNS setup where the REVERSE address maps to exactly ONE name (there should not be multpiple PTR records).
(The other names should preferably using CNAMES pointing to the "real" name).
(part of bind-tools in most distributions).
forward lookup with:
dig srv1.yourdomain.whatever
dig mydomain.yourdomain.whatev
This should show the A records.
if you do a revers lookup
dig -x the.ip.address.ofthesystem
This should show the PTR records.
there is a requirement from DNS setup where the REVERSE address maps to exactly ONE name (there should not be multpiple PTR records).
(The other names should preferably using CNAMES pointing to the "real" name).
1) First start with the why of your design.
2) Round Robin IPs != HA (in classic HA sense).
Round Robin IPs == Load Balancing.
3) You can easily place reverse (PTR) DNS records with your ISP or Hosting company. No problem with this.
And there's also no point, unless you're running an MTA on each IP.
4) For better help, open a new question describing your application, then ask for comments about how other people might design such a system.
2) Round Robin IPs != HA (in classic HA sense).
Round Robin IPs == Load Balancing.
3) You can easily place reverse (PTR) DNS records with your ISP or Hosting company. No problem with this.
And there's also no point, unless you're running an MTA on each IP.
4) For better help, open a new question describing your application, then ask for comments about how other people might design such a system.
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ASKER
I have added search mydomain.local entry to resolv.conf file and was able to resolve it.