This answer record details the known issues related to the Xilinx implementation of FLEXnet licensing for the 2013 Vivado and 14.x ISE Design Suite release.
For general questions about software licensing, see the following Xilinx Licensing FAQ page.
Xilinx Licensing Site:
Outstanding Known Issues in Vivado 2013.4
(Xilinx Answer 30526) - FLEXnet fails to find license when the computer default network interface is "eth1" (instead of "eth0")
(Xilinx Answer 33026) - Xilinx License Configuration Manager (XLCM) might take a long time to load the available licenses
(Xilinx Answer 33719) - XLCM shows only one available seat when a license file contains multiple entries of a feature
(Xilinx Answer 52062) - Floating IP license is not recognized in the Vivado tool if the IP license is on a different server than the Vivado license
(Xilinx Answer 52723) - XLCM does not handle paths with Simplified Chinese characters
Resolved Known Issues in Vivado 2013.4
(Xilinx Answer 57408) - Invalid warning given - "WARNING: [Common 17-301] Failed to get a license: Internal_bitstream"
Resolved Known Issues in Vivado 2013.3
(Xilinx Answer 56505) - The HOST ID matches column in XLCM is shown as NO in 2013.2 XLCM
(Xilinx Answer 56630) - License check fails for IP with old style license check (e.g. IP cores imported from ISE designs and certain 3rd party IP cores)
(Xilinx Answer 56696) - Vivado 2013.2 does not find the Design Linking (Simulation Only) licenses available with install
(Xilinx Answer 57474) - Vivado HLS license Error when using a USB Dongle - [LIC-104] Missing required feature [VIVADO_HLS]
Resolved Known Issues in Vivado 2013.2
(Xilinx Answer 55509) - 2013.1 / 14.5 Licensing - FlexID-9 Hardware USB Dongles are not recognized by Vivado 2013.1 or ISE 14.5 design tools