Siemens SCALANCE XM-400 Configuration Manual page 61

Virtual connection
Each area must be connected to the backbone area. In some situations a direct physical
connection is not possible. In this case, a router of the relevant area must be connected to a
backbone router via a virtual connection.
LSA types
Within the autonomous system, packets are exchanged that contain information about the
connections of a router and the connection status message. The packets are also known as
LSAs (Link State Advertisements). The LSAs are always sent from the router to the neighbor
router.
If there are changes in the network, LSAs are sent to all routers in the network. The information
depends on the LSA type.
SCALANCE XM-400/XR-500 Web Based Management (WBM)
Configuration Manual, 05/2017, C79000-G8976-C248-12
Technical basics
4.8 Routing function
61