vCenter Appliance Management Interface fails to start due to IPv6 loopback binding error

Products

• VMware vCenter Server

Issue/Introduction

When attempting to access the vCenter Appliance Management Interface (VAMI) console, you may observe that the underlying applmgmt service fails to start.

The following error is logged in the /var/log/vmware/applmgmt/applmgmt.log file:

[11046]ERROR:vmware.vherd.transport.server:Cannot listen: Couldn't listen on ::1:8201: [Errno 99] Cannot assign requested address.

Running ifconfig -a reveals that the lo (loopback) adapter lacks the inet6 ::1 entry

Environment

VMware vCenter Server Appliance

Cause

The kernel parameter net.ipv6.conf.lo.disable_ipv6 is set to 1 in both runtime parameters and persistent configuration, explicitly disabling IPv6 address processing on the loopback (lo) adapter.

Internal vCenter Server management communications (applmgmt) require binding to the IPv6 loopback address (::1) on port 8201. Because IPv6 is disabled on the loopback interface, the system cannot assign the requested sockets, causing the applmgmt service to crash on startup ([Errno 99] Cannot assign requested address)

Resolution

To resolve this issue, re-enable IPv6 address processing on the loopback adapter:

1. Log into the vCenter Server Appliance via SSH as **root

2. Verify the current parameter value

   sysctl net.ipv6.conf.lo.disable_ipv6

3. Edit /etc/sysctl.conf and update or add the following entry

   net.ipv6.conf.lo.disable_ipv6 = 0

4. Apply the persistent kernel settings

   sysctl --system

5. Verify the interface state using ifconfig lo to ensure inet6 ::1 is active

6. Start the appliance management service

   service-control --start applmgmt