SAP HANA system replication and the Internal Hostname resolution parameter:

[Former Member]

BACKGROUND:

We have a Production HANA landscape on HANA 1.0 SPS12 with a 4+0 Scaleout setup with HANA System replication to TIER2 in the same Primary Datacenter and TIER3 in the Secondary Datacenter
Recently we started receiving the alerts from our monitoring tool:
Internal communication is configured too openly
ISSUE:

We followed the SAP note 2183363, and updated the 'listeninterface' and 'internal_hostname_resolution' HANA parameters on our non prod systems in a similar scaleout setup.
After a validation on the non prod systems the change was made on our Production landscape that is using the HANA System Replication (HSR)
At the time of the parameters change in Production both TIER2 and TIER3 systems were stopped and removed from Replication setup
A full sync was triggered to TIER2 and after the completion the TIER3 full sync was triggered
Surprisingly the TIER3 system replication status did not show up on the Replication monitor in HANA studio
This has never occurred in the past as the System Replication monitor immediately reflects the TIER3 as soon as the Replication is configured

SOLUTION:

Further checks confirmed each volume from TIER2 was indeed replicating to TIER3 and it took the same amount of time it usually takes to synchronize, yet no signs of the TIER3 on HANA Studio Replication monitor
After some more checks we identified the 'listeninterface' and 'internal_hostname_resolution' parameters were not updated on TIER2 and TIER3
So we followed the below steps:
1. Stopped the Replication to TIER2 and TIER3 and removed them from the system replication configuration
2. Updated the 'listeninterface' and 'internal_hostname_resolution' parameters for the respective TIER as they are unique for every landscape
3. Started the full sync to TIER2
4. After TIER2 full sync completed, triggered the TIER3 full sync
These steps helped resolve the issue and the System Replication monitor was now reflecting all 3 TIERS
I have not come across much documentation on this topic and not sure if any customer experienced such a behavior so put up a post to describe the scenario
Would be good to have any feedback from any customers that have come across this and it will be useful for any customers that are planning to make this change in their landscape