Home » Server Options » RAC & Failsafe » Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services (Oracle Standard 11gR1, Red Hat Enterprise Linux (x86) 5.7)
Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553081] Tue, 01 May 2012 12:19 Go to next message
meclo
Messages: 4
Registered: May 2012
Location: Canada
Junior Member
Hi all,

Long time listener (no pun intended!), first time caller here.

I have an interesting dilemma that I'm trying to work through, and was hoping someone could offer guidance.

I have a 2-node Oracle Standard 11gR1 RAC that is sitting in our DMZ, which will be accessed by both internal and external (internet) clients. Is it possible to configure different RAC database services (one internal, one external) and have the services redirect to different hostnames or IP's (internal IP address/hostname vs external IP address)?


The problem I'm seeing is that if an instance redirect has to occur (Ex. if client initially connects to instance01 but is redirected to instance02 because that's where the service is currently active), the RAC will pass back the VIP hostname where the instance resides, which an external client won't be able to resolve (even if the tnsnames.ora file on the client has IP's instead of hostnames).

Perhaps my issue is understanding how the RAC gets the hostname to pass back to the client; I thought that came from the local_listener parameter within the database but my experimentation seems to have proven that theory wrong.

The simplest solution to this would probably be a local host entry or DNS alias at the client sites, but I'm not sure this is possible (we're communicating with our clients about this now but we've encountered some resistance).

Any insight into how to deal with this would be greatly appreciated.

Thanks!
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553082 is a reply to message #553081] Tue, 01 May 2012 12:29 Go to previous messageGo to next message
BlackSwan
Messages: 21938
Registered: January 2009
Senior Member
some, many, most applications these days are 3-tier; not 2-tier (direct client/server).

Clarify whether 2-tier or 3-tier application.

what software that runs on the remote client system interfaces with your site & the DB servers?
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553085 is a reply to message #553082] Tue, 01 May 2012 14:10 Go to previous messageGo to next message
meclo
Messages: 4
Registered: May 2012
Location: Canada
Junior Member
I believe some clients use sqlplus to access the database directly, and others use a 2-tier application (written by us).

We may be able to get the hostname to resolve externally as well, I'm told; if the multiple services angle doesn't work, how can I reconfigure the RAC to redirect to "hostname-vip.domain.com" rather than just "hostname-vip"?
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553086 is a reply to message #553085] Tue, 01 May 2012 14:19 Go to previous messageGo to next message
BlackSwan
Messages: 21938
Registered: January 2009
Senior Member
>Perhaps my issue is understanding how the RAC gets the hostname to pass back to the client
Networking 101 says that packets are exchanged based upon IP#; not hostnames.
hostnames are for people while Networking hardware uses strictly IP#.

> how can I reconfigure the RAC to redirect to "hostname-vip.domain.com" rather than just "hostname-vip"?
It appears that your perspective is different from my perspective.
Oracle relies upon OS for any & all network interaction.
Any & all networking configurations are done external to Oracle.
This problem & solution really have nothing to do with RAC; but everything to do with OS/Networking configuration.
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553087 is a reply to message #553086] Tue, 01 May 2012 14:34 Go to previous messageGo to next message
meclo
Messages: 4
Registered: May 2012
Location: Canada
Junior Member


The hostnames for my RAC nodes are "ext-racnode01.domain.com" and "ext-racnode02.domain.com". The RAC VIP's are called "ext-racvip01" and "ext-racvip02". In the event that the RAC has to redirect a client connection to a different instance, is there a way to configure the RAC to redirect to "ext-racvip0x.domain.com" instead of just "ext-racvip0x"? I'm assuming this is done from within the RAC somewhere, since the "ext-racvip0x" names are not configured anywhere outside of the RAC clustering software (as far as I know). Let me know if I'm mistaken.

Thanks!
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553128 is a reply to message #553087] Wed, 02 May 2012 01:31 Go to previous messageGo to next message
John Watson
Messages: 4081
Registered: January 2010
Location: Global Village
Senior Member
This is a bit confused, but I'll try.
First, as BS says, it is IP addresses that matter, not names.
Second, you are using 11.1, so the fixed and virtual names are static and resolved in hosts files and/or DNS (it will be different when you upgrade to 11.2)
Third, release 11.1 clusterware can really only failover one IP address per node. So you will almost certainly NOT be able to have automatic VIP failover for both networks. You'll have to manage your VIPs manually.
Fourth, directing the sessions using services is easy. Configure your listeners to listen on both the internal and external address, and create two services: make each sevice "preferred" on one node and "available" on the other.

hth, John.
Re: Can I configure an 11gR1 RAC to redirect to different hostnames/IP's based on services [message #553179 is a reply to message #553128] Wed, 02 May 2012 08:29 Go to previous message
meclo
Messages: 4
Registered: May 2012
Location: Canada
Junior Member
Thanks John and BlackSwan for your replies. I've read a bit about SCAN and it seems like that might have been helpful in this situation, but there's nothing to be done about that (at this point anyway).

I was able to get the RAC to redirect to the FQDN rather than the hostname; the solution was in the tnsnames.ora file after all, I just needed to restart the database along with the listeners (didn't know that). So I think I'll be alright once I get our network guy to add the hostnames to our external DNS and make those names resolvable from the outside.

Cheers!
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