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Hostname, Virtual Names and DNS.

Former Member
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We're working on a deployment of SAP (many modules). I'm looking at solidifying a strategy for hostnames, virtual names and DNS naming.

We'll be deploying on Linux (SUSE) or AIX (platform hasn't been decided), just in case it makes a difference.

What I'm trying to gather is, what reverse entries are needed, what should they resolve to, do they have to resolve correctly only during the installation etc. This will help me understand how many IPs we'll require per instance of each module.

For instance:

(Physical Server Hostname)

RK01ROW0103.domain.com 10.10.10.10

Virtual Host Names

ERPDEVAPP.domain.com (can this be a cname to RK01ROW0103 or will the reverse return of RK01ROW0103 break this? I know it does during installation)

If the same host houses both DB and APP we'd have:

ERPDEVDBS.domain.com (can this be a cname to RK01ROW0103 or will the reverse return of RK01ROW0103 break this? I know it does during installation)

What I'd like to understand is, does the ERPDEVAPP.domain.app have to be a virtual alias within the host that'll have a different IP so that the reverse lookup was correct?

Can someone that's on linux provide a non company confidential output of what their /etc/hosts and dns strategies are? I'm really trying to grasp this prior to entering into our development lifecycle.

Thank you for the help.

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Answers (3)

Answers (3)

Former Member
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lets start with simple cluster configuration.

We start with two servers here:

sapserver1 with physical ip 10.10.10.11

sapserver2 with physical ip 10.10.10.12

then we assign logical ip address to services via cluster:

db_ip_service with logical ip 10.10.10.21

ap_ip_service with logical ip 10.10.10.22

then we add entry to hosts file for both servers:

*physical hostname

sapserver1 10.10.10.11

sapserver2 10.10.10.12

*logical hostname

sapdb 10.10.10.21

sapap 10.10.10.22

so when assigned the db_ip_service to sapserver2 in cluster configuration, it automatically turned into sapdb(by host file determination in this case).

Former Member
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In case you use SUSE, you might have a look at:

http://www.novell.com/saptechdocs

The concept of virtual hostnames is also described there.

Former Member
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Do you ever have a friendly name that the failover cluster points to?

For example, our hostnames are geographically based, and not based on function. I want an alias that will utilize a friendly name for functionality.

Will that need to sit on a different adapter, since the reverse lookup will break the installation? Or should I just throw into the hosts file the friendly name during the installation, then remove later (note the installation is done with the friendly name, not the physical host name).

Are there more people that have real world examples?

Former Member
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Hi Ben,

We use the Veritas Cluster Server on Linux x86_64. We have a three node cluster, two in production and one node in DR.

It was installed using a virtual name which resolves to a site dependent virtual name which then resolves to the physical hostname on which the cluster node is active on.

sapprod.domain ---> sapinstance -


> prodserver1 OR

-


> prodserver2

sapprod.domain ---> sapdrinstance -


> drserver1

The installation was done with the sapprod name.

Hope it helps!

Cheng

former_member189546
Active Contributor
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Hello,

Normally only need virtual names if you have a failover system.

Best to carefully read the installation guides they are quiet detailed.

www.service.sap.com/instguides

regards,

John Feely

Former Member
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Any help would be greatly appreciated, and points will be given to the best answer.

Thank you.