HANA System Replication using internal hostnames

[#1]

Hello,

I had HANA System Replication enabled between Primary (sapshdb001) and Secondary (sapshdb002) system using public network interface i.e. using same IP range that SAP application uses to connect to HANA. That worked completely fine.

I am now trying to secure HSR using separate internal network defined within HANA system topology by system_replication_hostname_resolution from global.ini and not /etc/hosts config.

As per Host Name Resolution for System Replication documentation, I've defined listeninterface parameter from system_replication_communication to .global and defined system_replication_hostname_resolution section as

10.5.2.1 sapshdb002 - at System level on Primary system
10.5.1.1 sapshdb001 - at System level on Secondary system

As per documentation, above minimum configuration should have worked but I see erros in nameserver trace on Secondary as attached. I've also raised incident with SAP with no resolution as yet. It would be really helpful to know if anyone have done similar setup and how.

Please Note: HANA release is 2.0 SP 04
Firewall at OS level is disabled on both Primary and Secondary, also there's no firewall between Priamry and Secondary. Again as I mentioned earlier, not using separate internal network but public, HSR had worked fine.

Thanks.

Best Regards,
Kashyap Shah

[dennispadia · Accepted solution]

Hello Kashyap,

In Secondary Server, you have maintained below value in system_replication_hostname_resolution but you have to make sure that 10.5.1.1 IP is attached to the server sapshdb001

10.5.1.1 sapshdb001

Below is example, 192.168.99.33 IP is been used for hana01 server and that same IP is attached in hana01 which you can find using ip addr show

Make sure your internal IPs are attached to each host before you set it as parameter in HANA.

Regards,

Dennis Padia.

[ravindrakumartbc]

Hi Kashyap, thanks for your response . we have followed what you had advice in your thread .

below is our setup .

Redhat scale up HA cluster . Two hana standalone nodes on two Redhat boxes. Isolation is enabled.

HANA client Lan is 10.250.150.x . when i enabled replication by using this lan all work fine.

in order to make replication traffic on separate lan i assign replication host name in global.ini as 10.250.145.x than our replication wont work , throw error regarding 40002 ports error.

trying to follow below blog from SAP. but issue remain the same .

https://help.sap.com/viewer/6b94445c94ae495c83a19646e7c3fd56/2.0.01/en-US/c0cba1cb2ba34ec89f45b48b21...

[ravindrakumartbc]

Hi Kashyap , i am also using the similar setup . both internal IP series are assigned and reachable from each host .

still having issue while setting up the replication . any other findings from your side.

[kashyap_shah3]

My issue was resolved and the main cause was that internal hostnames weren't reachable from HSR node which is a prerequisite.

It's been a while though. So, if you describe you issue with exact errors, I may be able to help more.

Cheers.

[kashyap_shah3]

I've been able to fix the issue by attaching internal IP to the same NIC on Primary and Secondary. So although, /etc/hosts or DNS config isn't required as per SAP documentation, IPs have to be defined at network level and must be reachable.

So Deniss's first reply is the solution.

Thanks.

Best Regards,
Kashyap Shah

[kaus19d]

Hi Kashyap Shah,

Would suggest you to get in touch with your organisation network colleagues to get the network routes

Thanks,

Kaushik

[dennispadia]

Hello Kashyap,

Did you try to check the firewall? I think the port is blocked. System replication use different port.

Regards,

Dennis Padia.

[kashyap_shah3]

Hi Dennis,

As I'd mentioned in my Note:
Firewall at OS level is disabled on both Primary and Secondary, also there's no firewall between Priamry and Secondary. HSR had worked fine on public network interface.
I think now the question is: does internal IP have to be attached to network card interface (visible in ifconfig output) ? As I haven't done that. It's not clear from SAP documentation as well.

Thanks.

Best Regards,
Kashyap Shah

[kashyap_shah3]

Hi Dennis,

I understand if internal IP is attached to the network interface, that would work.

I'm trying to implement as per following statement from SAP Help link that I've provided:
"For system replication it is not necessary to edit the /etc/hosts file, internal ('virtual') host names must be mapped to IP addresses in the global.ini file to create a dedicated network for system replication"

So, I've maintained internal host names to IP address mapping in global.ini --> [system_replication_hostname_resolutio] section.

Please let me know if you interpret SAP Help documentation in a different way.

Thanks.

Best Regards,
Kashyap Shah