Resolving many agents not being able to connect to pools

Introduction: In certain situations, you may encounter an issue where a large number of virtual machines (VMs) in Horizon pools are in an "Agent Unreachable" state, preventing Agents, BPO Agents, etc from connecting. This article provides a solution to resolve this issue by rebooting the connection server.

Problem Description:

Symptoms: Many agents are unable to connect to Horizon pools. A significant number of VMs are stuck in an "Agent Unreachable" state.
Impact: Users attempting to start new sessions cannot connect, as the VMs are unavailable.

Solution: Rebooting the Connection Server

Step-by-Step Instructions:

Identify the Problem:
- Monitor the status of the Horizon pools and VMs to identify the extent of the issue.
- Confirm that a large number of VMs are in the "Agent Unreachable" state.
- Usually there will be a UAG that is displaying errors in the console as well. Monitor>Dashboard>System Health>Gateway Servers
Reboot the Connection Server:
- RDP to the primary connection server OKIOPRDHCS01
- Reboot the server.
- Monitor status and verify that it comes back online.
Verify the Solution:
- Monitor the status of the VMs in the Horizon pools.
- Ensure that the "Agent Unreachable" state has been resolved and that agents can now connect to the VMs.
- Confirm that new sessions can be started without issues.

Conclusion: Rebooting the connection server is an effective solution to resolve the "Agent Unreachable" state in Horizon pools. While this action may temporarily affect users attempting to start new sessions, it ensures that existing sessions remain connected and restores normal functionality for all users.