For some reason TFTP and so far just TFTP is failing on all guests on esxi 4 for me. I have it installed on a Dell SC1435 and a Dell M610, both with very simple single-interface default networking configs.

When I boot up a new VM it dhcp's and gets its IP fine, but it times out at the tftp stage (my dhcp server is handing out the next-server and filename fields as part of a cobbler setup).

Here's some things I've tried to narrow it down.

• using a separate M610 in the same blade chassis on the same network I can PXE boot a centos 5.3 install without issue
• running centos 5.3 on that blade I can then use the cli tftp client to fetch the /pxelinux.0 file no probem.
• tcpdumping on the tftp server it never sees the request (when it comes from a guest)
• uploading a centos ISO to the datastore on the esxi server and building the vm from there works. That vm can then be ssh'd into, and can run yum update, but it cannot tftp (dns works too)
• running a tftp server on the guest vm no other hosts can tftp fetch a file from it, so its both tftp in and tftp out failing

So whether its the bios/pxe-boot tftp client or the centos 5.3 tftp client neither work when the host is a guest on an esxi 4 server. However both work on the same hardware via the same network config if the physical host is running centos instead.