Failed to restart TFTP issue

[SebastianRoth]

(2017-07-18 09:30)richard_chen Wrote:  3. Condition for issue happend
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1) there lots of NB in network, if there have 100 NB, it can boot normal

To me this sounds as if your TFTP server cannot handle all the requests if there are "too many". As already mentioned this has nothing to do with iPXE.

(2017-07-18 09:30)richard_chen Wrote:  2) more than DHCP&iPXE servers, if only have one DHCP&iPXE, it can boot normal

What do you mean by iPXE server? TFTP server hosting the iPXE binary or HTTP server hosting the iPXE script? Possibly you have your DHCP servers configured differently. In this case you'd see client boot properly sometimes but fail when clients get an answer from a DHCP server giving false information.

(2017-07-18 09:30)richard_chen Wrote:  ... we checked the packets of wireshark for normal boot iPXE NB, ...

How and where did you capture the packets? Next to the client (using a hub or mirror port on the switch) or on the server - which server exactly? As you seem to have several servers for DHCP/TFTP you better capture on the client side to make sure you don't miss any packets...