9. Half-truth: You can use MPLS TE only within a single OSPF area. Inter-area MPLS traffic engineering is available (see also detailed description) but has severe limitations:
- The MPLS TE path cannot be computed automatically. You have to manually specify at least the Area Border Routers (ABRs) the MPLS TE path crosses;
- Automatic mapping of IP traffic onto MPLS TE paths (autoroute) is not available as the router establishing the MPLS TE path does not know the exact topology of other OSPF areas.
- Inter-area MPLS TE paths cannot be re-optimized after they have been established.
Note: The same is true for IS-IS. Truly dynamic MPLS TE tunnels can be established within a single IS-IS level but they can cross the level boundary if you manually configure the transition points.
10. No longer true: You can't differentiate customer traffic based on Class-of-Service if you use MPLS TE The technology itself never had this limitation but Cisco IOS did not support multiple parallel tunnels carrying different traffic classes for a long time.
About the author: Ivan Pepelnjak CCIE No. 1354 is a 25-year veteran of the networking industry. He has more than 10 years of experience in designing installing troubleshooting and operating large service provider and enterprise WAN and LAN networks and is currently chief technology advisor at NIL Data Communications focusing on advanced IP-based networks and web technologies. His books include MPLS and VPN Architectures and EIGRP Network Design. You can read his blog here: http://ioshints.blogspot.com/index.html.