Unable to change the network speed on RHEL VM running on VMware. Why ?

Issue

• The VMWare ESX server's NIC Card speed is 1GBPS only but the network speed has set to 10GBPS on RHEL VM.
• Unable to change the speed / negotiation manually on any of the RHEL VMs running on VMWare ESX.

[root@HOSTNAME ~]# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   1000baseT/Full
                                10000baseT/Full
        Supports auto-negotiation: No
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: No
        Speed: 10000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 0
        Transceiver: internal
        Auto-negotiation: off
        MDI-X: Unknown
        Supports Wake-on: uag
        Wake-on: d
        Link detected: yes
[root@HOSTNAME ~]#