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Number of NIC's and DNS

Former Member
0 Kudos

I've asked similar question before, but this is different enough for me to warrant another thread.

We're deploying a new SAP environment on SLES.

Currently we're deploying with a single NIC and a single IP with the AHOST record and PTR record pointing to the hostname. However, the SAP virtual name (e.g., devecc1) is a CNAME dns record to the hostname AHOST. Which means, the reverse lookup for devecc1 would return "hostname".

During the installation this will yell at you, therefore, we add the virtual name to the hosts file.

Is this the correct way to do it?

Or do you have 2 NIC's and 2 IP's.

One NIC for the hostname + ip address

One NIC for the virtualname + ip address

Or do you have 1 NIC with 2 IP's one being an Alias

One NIC for hostname + ip address

One Alias for virtualname + ip address

and if you do that, how do you ensure that SAP is listening on the correct interface?

Thank you for any help in advance.

Accepted Solutions (1)

Accepted Solutions (1)

former_member189546
Active Contributor
0 Kudos

Hello,

Please check...

124562 Hostname resolution problems (DNS timeouts)

1624061 Use of virtual TCP/IP host names

129997 Hostname and IP address lookup

regards,

John Feely

Former Member
0 Kudos

Thank you John. The following note answered pretty much everything:

1624061

I also gave reward points to all who helped, because I like hearing real world implementation usage etc.

Thank you.

Answers (1)

Answers (1)

isaias_freitas
Advisor
Advisor
0 Kudos

Hello Ben!

I believe that if you delete the CNAME entry at the DNS, and create the AHOST and PTR records for the virtual hostname as well, then it should work.

Best regards,

Isaias

Former Member
0 Kudos

Isaias,

Thank you for the response. However, if you have 2 AHOST and 2 PTR records, the PTR records will be round robin, which will give mixed results for things like Backups (NetBackup), or Configuration management (puppet) as both rely on reverse lookup resolution.

isaias_freitas
Advisor
Advisor
0 Kudos

Hello Ben,

You're welcome!

Yes, you are correct.

SAP also uses reverse lookups.

Maybe it would be better if you have another IP address (a "virtual IP address") assigned to the virtual hostname. This way both the hostname and the virtual hostname will have their own AHOST and PTR records, and one will not influence at the other.

Then, at the SAP profiles, you just need to point the below parameters to the virtual hostname (wherever this would be appropriate), and you should be fine.

SAPLOCALHOST

SAPLOCALHOSTFULL

SAPGLOBALHOST

Regards,

Isaias

Former Member
0 Kudos

That's what the plan is. Thank you..

To standardize we'll likely do the the same across all DB only and APP / DB etc.

I'll award points after giving some others time to provide input.