13.3.1.3.2. Signaling Flow Survivability for “Direct Link“
Access Points 
Figure 230. Survivability router configuration
The following process must be taken into consideration when configuring
the survivability router.
Normal operation (without survivability):
-
CC-A generates packet at signaling unit AP 18 with destination 192.168.200.9 and source 192.168.1.1 and transfers it to the internal signaling router associated with AP 18 (192.168.1.18).This sends the packet to the signaling unit AP 18 (192.168.200.9).Survivability:CC-A generates packet at AP 18 with destination 192.168.200.9 and source 192.168.1.1 and transfers it to the router R1 under 192.168.1.101.
IMPORTANT:
The complete IP frame, including addresses, remains identical to the frame in normal operation. With survivability, only the accessed router changes (in the OpenScape 4000 LAN segment). This change takes the form of a different destination address at Ethernet level (MAC-DA). The IP address of Router R1 in the OpenScape 4000 LAN segment is not accessed visibly. It is needed to determine the MAC address of the router port with ARP.R1 sends the packet to the next hop router 192.168.15.18 and creates the modem link for the PPP connection between 192.168.15.1 and 192.168.15.18 or uses the existing connection.The packet is sent from the PPP instance 192.168.15.18 to the destination 192.168.200.9 in AP 98.For this, the route for 192.168.200.9 must be configured via 192.168.15.18 in the survivability router R1 and the dial-up connection for the destination 192.168.15.18.The PPP instance in R1 must be configured with the address 192.168.15.1 so that packets from AP 18 can be transported back to CC-A.