ConfigMgr migration, PXE Provider shutdown (SMSPXE)

Today I did another ConfigMgr upgrade from SP1 to R2 with 3 remote Distribution points (DPs). Nothing to worry you will say. After the upgrade (which was 100% fine) the Primary server and 1 remote DP was working fine. Deployment could be done, everything okay. Nothing to see in Site and System status. The other 2 remote DP's however didn't want to PXE boot because of error "PXE-E53: No boot filename received". Last line in SMSPXE.log was ================= PXE Provider shutdown. =====================

I did a lot of things after that:
-Restart WDS services
-Update both boot images and checked properties
-Restart multiple Site servers
-Checked logfiles (On primary and Site servers)
-Checked DHCP scope options
-Checked local security
-Checked SMS Component Manager
-Checked firewall status
-Checked no antivirus in place

SMSPXE.log was showing me the following lines:
-RequestMPKeyInformation: Send() failed.
-Failed to get information for MP: http://FQDN. 80004005
-PXE::MP_InitializeTransport failed; 0x80004005
-PXE::MP_LookupDevice failed; 0x80004005
-RequestMPKeyInformation: Send() failed.
-Failed to get information for MP: http://FQDN. 80004005
-PXE::MP_InitializeTransport failed; 0x80004005
-PXE::MP_ReportStatus failed; 0x80004005
-PXE Provider failed to process message.
-Unspecified error (Error: 80004005; Source: Windows)
-98:4B:E1:7E:6D:89, 39C6D000-9BED-11E0-0000-984BE17E6D89: Not serviced.
-Cannot read the registry value of MACIgnoreListFile (00000000)
-MAC Ignore List Filename in registry is empty

Nothing didn't work here! When looking on MS TechNet they say you must reinstall WDS, PXE, DP all over again. Not exactly what I had in mind here. Long story short, after a few hours checking I rebooted the Primary Site server, restarted WDS services on both DPs again, and everything was working in a few minutes. First line in SMSPXE.log was now ================= PXE Provider loaded. =====================

Very happy with the (easy) solution, but very strange ConfigMgr didn't gave me an error. There's no mentioning of rebooting a Primary Site server after the upgrade also. Lessons learned: Reboot the Primary Site server and Site servers after an migration always.

Source:
Upgrade ConfigMgr 2012 SP1 to 2012 R2 Preview
Management Point PXE Boot Error 80004005 After SP1 Upgrade
SCCM 2012 R2 upgrade broken WDS/PXE
PXE-E53: No boot filename received