Redhat Inplace upgrade from Redhat Enterprise Linix 7.9 to 8.10. After successful completion not able to connect from inpremise networl

After an in-place Leapp upgrade from RHEL 7.9 to 8.10 on an Azure VM, the OS is up but network/SSH from on-premises is failing. Use Serial Console to verify and repair in this order:

1. Verify the upgrade completed cleanly
   From Serial Console:

      sudo cat /etc/redhat-release
      uname -r
      sudo dnf repolist
   

   This confirms the VM is actually on RHEL 8 and using RHEL 8 repositories, as expected after a successful Leapp upgrade.
2. Check that the network interface is up and has an IP
   Still in Serial Console:

      ip addr
      ip route
      nmcli device status
   

   Ensure:
   • The primary interface (usually eth0 or ens*) is connected.
   • It has the expected private IP from the Azure VNet.
   • There is a default route via the Azure gateway.
   If the interface is disconnected, bring it up with NetworkManager (RHEL 8 default):

      nmcli connection show
      nmcli connection up <connection-name>
   

3. Check local firewall on the VM
   RHEL 8 may have different firewalld defaults than RHEL 7:

      sudo systemctl status firewalld
      sudo firewall-cmd --list-all
   

   For testing from on-premises, temporarily stop the firewall (only as a diagnostic step):

      sudo systemctl stop firewalld
   

   Then test SSH from on-premises. If SSH works with firewalld stopped, add a permanent SSH rule instead of leaving it disabled:

      sudo firewall-cmd --permanent --add-service=ssh
      sudo firewall-cmd --reload
      sudo systemctl start firewalld
   

4. Verify SSH service on the VM

      sudo systemctl status sshd
      sudo ss -tlnp | grep 22
   

   Ensure sshd is active and listening on 0.0.0.0:22. If not:

      sudo systemctl enable --now sshd
   

5. Check Azure-side networking (from Azure portal)
   Since Serial Console works, the VM is running; the issue is likely network path:
   • Confirm the VM’s NIC and subnet NSGs allow inbound TCP 22 from on-premises (no higher-priority deny rules).
   • Confirm the VM still has the correct private IP and, if used, public IP or VPN/ExpressRoute connectivity from on-prem.
   • If a NAT gateway or custom route tables are used, verify they are unchanged and correctly associated with the subnet.
6. If Leapp-related issues are suspected
   If the upgrade was from 7.9 directly to 8.10 and there are unexplained issues, one supported mitigation is to upgrade via an intermediate minor version (for example, 8.8) using --target x.y, then move to 8.10 after confirming stability:

      sudo leapp upgrade --target 8.8
   

   After a successful intermediate upgrade and verification, repeat for 8.10 if required.

Once network interface, routing, firewall, and SSH service are confirmed healthy on the VM, and NSG/VNet configuration allows inbound SSH from on-premises, connectivity should be restored.

References:

• How to perform an upgrade for RHEL PAYG virtual machines using Leapp
• Troubleshooting Red Hat OS upgrade issues
• Red Hat Enterprise Linux in-place upgrades
• How to upgrade SAP-HANA and SAP-APPS PAYG virtual machines from RHEL 7.9 to RHEL 8.x using Leapp