Forwarding Address
1. Import external routes
In OSPF, external routes are imported from ASBR(Autonomous System Border Router) (Type 5 LSA)
2. External route calculation
External route type
E1 is superior to E2
E1 Internal routes are counted as trusted and treated the same as internal routes. Type-1 indicates close routes. Type-2 indicates unfamiliar routes
4. Generation of suboptimal external routes
OSPF runs between RTA and RTB
Run RIP between RTB and RTC to import RIP to OSPF. (RTB learns network 192.168.3.0 through RIP, but RTA cannot learn network 3.0 routes, so it can only learn network 3.0 through INJECTING RIP.) The next hop of network 3.0 learned through IMPORT A is 10.1.123.2. However, A and C are also in the same LAN, so A suboptimal path is generated. Forwarding Address resolves the suboptimal problem
Forwarding Address(only in Type-5 LSA)
The next hop and the interface of the external route reside on the same network segment
RTB: 10.1.123.2 RTC: 10.1.123.3
==Forwarding Address technology sets the next hop to 10.1.123.3, which resolves the suboptimal problem ==
