Re: ESXi 5.1 - Connect to localhost failed: Connection failure

Interesting.  What hardware are you running ESXi 5.1 on?  What is the hardware for this NIC?  Hopefully you verified it is supported under ESXi 5.1: http://www.vmware.com/resources/compatibility/search.php

Also, run these commands to list your installed VIBs and get info on the NIC driver being used.  This may help me determine if you're using an unsupported/outdated driver:

Check info on NICs and associated driver:

# esxcli network nic list

Example from one of our HP ProLiant servers, showing be2net driver being used.  I've edited output for simplicity:

Command to list VIBs installed.  Hopefully you're using a VMwareCertified driver that's compatible with your hardware + ESXi 5.1:

# esxcli software vib list

Example from one of our HP ProLiant servers, using a razor-thin custom ESXi 5.1 image:

~ # esxcli software vib list

Name                           Version                             Vendor           Acceptance Level  Install Date

-----------------------------  ----------------------------------  ---------------  ----------------  ------------

char-hpcru                     5.0.3.09-1OEM.500.0.0.434156        Hewlett-Packard  PartnerSupported  -

hp-smx-provider                500.03.01.10.2-434156               Hewlett-Packard  VMwareAccepted    -

hpacucli                       9.20-9.0                            Hewlett-Packard  PartnerSupported  -

hpbootcfg                      01-01.02                            Hewlett-Packard  PartnerSupported  -

ehci-ehci-hcd                  1.0-3vmw.510.0.0.799733             VMware           VMwareCertified   -

esx-base                       5.1.0-0.9.914609                    VMware           VMwareCertified   -

esx-dvfilter-generic-fastpath  5.1.0-0.0.799733                    VMware           VMwareCertified   -

esx-xlibs                      5.1.0-0.0.799733                    VMware           VMwareCertified   -

ipmi-ipmi-devintf              39.1-4vmw.510.0.0.799733            VMware           VMwareCertified   -

ipmi-ipmi-msghandler           39.1-4vmw.510.0.0.799733            VMware           VMwareCertified   -

ipmi-ipmi-si-drv               39.1-4vmw.510.0.0.799733            VMware           VMwareCertified   -

misc-cnic-register             1.1-1vmw.510.0.0.799733             VMware           VMwareCertified   -

misc-drivers                   5.1.0-0.0.799733                    VMware           VMwareCertified   -

net-be2net                     4.1.255.11-1vmw.510.0.0.799733      VMware           VMwareCertified   -

net-bnx2                       2.0.15g.v50.11-7vmw.510.0.0.799733  VMware           VMwareCertified   -

net-nx-nic                     4.0.558-3vmw.510.0.0.799733         VMware           VMwareCertified   -

scsi-hpsa                      5.0.0-21vmw.510.0.0.799733          VMware           VMwareCertified   -

scsi-lpfc820                   8.2.3.1-127vmw.510.0.0.799733       VMware           VMwareCertified   -

uhci-usb-uhci                  1.0-3vmw.510.0.0.799733             VMware           VMwareCertified   -

vmware-fdm                     5.1.0-947673                        VMware           VMwareCertified   -

hpnmi                          2.0.11-434156                       hp               PartnerSupported  -