13.1.2.2. Signaling Survivability via Alternate LAN 
With signaling survivability via alternate LAN, an alternative route
for signaling via a second LAN path is set up as soon as a fault in the
IP path is detected. Therefore, a survivability router on the central
system and a second LAN infrastructure on the access point/OpenScape
4000 SoftGate must be available. Then an alternate path is set up via
the survivability router on the central system and the second LAN on
the access point/OpenScape 4000 SoftGate. The signaling messages are
sent via this alternative path once it is established. This ensures that
none of the messages that may be in a backlog are lost.
There are two possible scenarios for signaling survivability via alternate
LAN:
- Using L2 Redundancy at access point/OpenScape 4000 SoftGate for input of alternative router
Figure 226. Signaling Survivability about alternatives LAN and L2 Redundancy
- Using 2nd ethernet interface of access point/OpenScape 4000 SoftGate for input of alternative router
Figure 227. Signaling Survivability about alternatives LAN and second Ethernet interface
If every access point/OpenScape 4000 SoftGate features an individual
survivability router, signaling survivability can cover even the total
failure of the WAN infrastructure. The only critical factor here are
the connection between the active CC and the survivability router(s)
in the OpenScape 4000 LAN segment and the independence of (failed) WAN
from the LAN used for survivability.