1. If your "/etc/hosts" file contains correct FQDN (fully qualified domain name) and IP addresse information. 2. It can also happen due to DNS setup issues. So please check if the namenode host is resolved to correct domain.
In some cases it can happen when the "hadoop.security.token.service.use_ip" property is set to "false" Can for testing can you try setting it to "true" once as following to see if it helps:
hadoop.security.token.service.use_ip (default=true) is needed
if your network is setup such that you need to use hostnames in
delegation tokens instead of ip addresses.
When (hadoop.security.token.service.use_ip = true) there is a lookup done on the IP address of the sender, which is compared to the SPN in the token. You can add this property inside your "core-site.xml"