Explain that old Intel PXE stacks have allergy to PMTU discovery.

diff --git a/pxelinux.doc b/pxelinux.doc
index ba4b008..539ea4e 100644 (file)
--- a/pxelinux.doc
+++ b/pxelinux.doc
@@ -80,10 +80,10 @@ Lefebvre:
        ftp://ftp.mamalinux.com/pub/atftp/
 
 Unfortunately, the Intel LANDesk Service Agent II prior to version
-0.99h (PXE PDK V2.4) seems to have a rather serious bug: it requests
-the TFTP "blksize" option, but will be mortally confused if this
-option is actually accepted by the server!  There are three possible
-workarounds for this bug:
+0.99h (PXE PDK V2.4) seems to have a host of serious bugs.  Among
+other things, it requests the TFTP "blksize" option, but will be
+mortally confused if this option is actually accepted by the server!
+There are three possible workarounds for this bug:
 
 1. Use a TFTP server with doesn't support "blksize".
 
@@ -101,6 +101,14 @@ workarounds for this bug:
    request the "blksize" option if it has tried MTFTP and failed.
    These DHCP options are beyond the scope of this document.
 
+These systems also break if PMTU discovery is enabled on the TFTP
+server.  This has to be disabled in the kernel on the TFTP server.  On
+Linux, you can disable PMTU discovery by setting:
+
+       echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc
+
+Note that this may cause bad performance for other services on the machine.
+
 
     ++++ SETTING UP THE DHCP SERVER ++++