I came along an interesting issue at work and was able to reproduce it in the lab . Sharing the way to fix it , while we check further for the cause of it.
Below were the steps performed to reproduce the problem
1. Build psca.xxxx.com by ISO. Site name “Default-First-Site”, Domain name “vsphere.local”.
2. Build pscb.xxxx.com by ISO and join psca.xxxx.com
3. Build vCenter instance “vcsa6.xxxx.com” by ISO and connect to psca.xxxx.com
4. Repoint vCenter instance to “pscb.xxxx.com” by KB 2113917.
5. Test Web Client and vSphere Client.
6. Reboot the 3 VMs and test again.
7. Disconnect network of vCenter instance VM.
8. Change DNS name of vCenter instance to different IP address on DNS server. >> Done successfully
9. Change IP address of vCenter instance to new IP by DCUI or command line. (I tested this with vami change through ssh as well as console UI on vcenter 6)
10. Connect network of vCenter instance VM.
11. Restart vCenter services and test again. (Web client fault here)
A server error occurred.
 SSO error: Cannot connect to the VMware Component Manager https://vcsa6.xxxx.bng/cm/sdk?hostid=fbf7282a-f940-4f6d-8180-58b1476c3e72
Check the vSphere Web Client server logs for details.
Error seen on vsphere-client-virgo.log for web-client under /var/log/vmware/vsphere-client .
[2016-01-18T11:46:43.240Z] [INFO ] http-bio-9090-exec-9 com.vmware.vise.util.session.SessionUtil Generated hashed session id: 100001
[2016-01-18T11:46:43.243Z] [INFO ] http-bio-9090-exec-9 70000001 100001 ###### com.vmware.vise.util.i18n.I18nFilter The preferred locale for session 100001 is set to: en_US
[2016-01-18T11:46:44.909Z] [INFO ] http-bio-9090-exec-9 70000001 100001 ###### com.vmware.vise.vim.cm.impl.ComponentManagerServiceImpl Retry wont be attempted for error: java.net.NoRouteToHostException: No route to host
[2016-01-18T11:46:44.917Z] [ERROR] http-bio-9090-exec-9 70000001 100001 ###### com.vmware.vise.vim.cm.impl.ComponentManagerServiceImpl Error when creating component manager service com.vmware.vim.vmomi.client.exception.ConnectionException: java.net.NoRouteToHostException: No route to host
at com.sun.proxy.$Proxy474.retrieveServiceInstanceContent(Unknown Source)
It clearly mentions as “”no route to host “.
At this point I tested forward /reverse lookup which was working fine , pings to both psca and pscb were working fine .
So , I repointed the vcsa back to psca and to my surprise the web-client started working fine.
Got the repoint done again back to pscb , and it failed again with the same error .
Post multiple log checks found that the /etc/hosts file on the vcsa still was having the old ip address although the new ip change was completed at step9.
Configured the hosts file with the correct ip address and restarted all services using command “service-control –stop -all ” and “service-control –start -all ”
Now , once the web-client came up it was loading fine , and it was still pointed to pscb.xxxx.com