diff --git a/devstack/lib/ironic b/devstack/lib/ironic
index d559f3a36f..b69ad39e89 100644
--- a/devstack/lib/ironic
+++ b/devstack/lib/ironic
@@ -128,6 +128,7 @@ IRONIC_TEMPLATES_DIR=${IRONIC_TEMPLATES_DIR:-$IRONIC_DEVSTACK_DIR/tools/ironic/t
 IRONIC_BAREMETAL_BASIC_OPS=$(trueorfalse False IRONIC_BAREMETAL_BASIC_OPS)
 IRONIC_TFTPBOOT_DIR=${IRONIC_TFTPBOOT_DIR:-$IRONIC_DATA_DIR/tftpboot}
 IRONIC_TFTPSERVER_IP=${IRONIC_TFTPSERVER_IP:-$HOST_IP}
+IRONIC_TFTP_BLOCKSIZE=${IRONIC_TFTP_BLOCKSIZE:-$((PUBLIC_BRIDGE_MTU-50))}
 IRONIC_VM_COUNT=${IRONIC_VM_COUNT:-1}
 IRONIC_VM_SPECS_CPU=${IRONIC_VM_SPECS_CPU:-1}
 IRONIC_VM_SPECS_RAM=${IRONIC_VM_SPECS_RAM:-1280}
@@ -2143,6 +2144,7 @@ function configure_tftpd {
     [ -f /etc/init/tftpd-hpa.conf ] && echo "manual" | sudo tee /etc/init/tftpd-hpa.override
     sudo cp $IRONIC_TEMPLATES_DIR/tftpd-xinetd.template /etc/xinetd.d/tftp
     sudo sed -e "s|%TFTPBOOT_DIR%|$IRONIC_TFTPBOOT_DIR|g" -i /etc/xinetd.d/tftp
+    sudo sed -e "s|%MAX_BLOCKSIZE%|$IRONIC_TFTP_BLOCKSIZE|g" -i /etc/xinetd.d/tftp
 
     # setup tftp file mapping to satisfy requests at the root (booting) and
     # /tftpboot/ sub-dir (as per deploy-ironic elements)
diff --git a/devstack/tools/ironic/templates/tftpd-xinetd.template b/devstack/tools/ironic/templates/tftpd-xinetd.template
index 5f3d03f3bb..ec84b0588f 100644
--- a/devstack/tools/ironic/templates/tftpd-xinetd.template
+++ b/devstack/tools/ironic/templates/tftpd-xinetd.template
@@ -6,7 +6,7 @@ service tftp
   wait            = yes
   user            = root
   server          = /usr/sbin/in.tftpd
-  server_args     = -v -v -v -v -v --map-file %TFTPBOOT_DIR%/map-file %TFTPBOOT_DIR%
+  server_args     = -v -v -v -v -v --blocksize %MAX_BLOCKSIZE% --map-file %TFTPBOOT_DIR%/map-file %TFTPBOOT_DIR%
   disable         = no
   # This is a workaround for Fedora, where TFTP will listen only on
   # IPv6 endpoint, if IPv4 flag is not used.
diff --git a/doc/source/install/configure-pxe.rst b/doc/source/install/configure-pxe.rst
index 0a14c1eae3..659500722e 100644
--- a/doc/source/install/configure-pxe.rst
+++ b/doc/source/install/configure-pxe.rst
@@ -63,6 +63,17 @@ node(s) where ``ironic-conductor`` is running.
 
        sudo systemctl restart xinetd
 
+.. note::
+
+  In certain environments the network's MTU may cause TFTP UDP packets to get
+  fragmented. Certain PXE firmwares struggle to reconstruct the fragmented
+  packets which can cause significant slow down or even prevent the server from
+  PXE booting. In order to avoid this, TFTPd provides an option to limit the
+  packet size so that it they do not get fragmented. To set this additional
+  option in the server_args above::
+
+    --blocksize <MAX MTU minus 32>
+
 #. Copy the PXE image to ``/tftpboot``. The PXE image might be found at [1]_:
 
    Ubuntu (Up to and including 14.04)::