Hello Mohammed
Let’s say you have this topology:
Let’s assume that R1 has a default route in its routing table via the interface connected to the Internet.
Now if you have the default information originate command in R1, then:
- R2 will install in its routing table a default route via OSPF with a next hop of 192.168.12.1 when there is a default route in the routing table of R1.
- If the internet interface of R1 goes down, or if an administrator manually removes that default route from the routing table, R2 will be informed via OSPF, and will no longer have a default route via 192.168.12.1.
Now if you have the default information originate always command in R1, then:
- R2 will learn of a default route via 192.168.12.1 and will install this in R2’s routing table, regardless of whether or not R1 has a default route installed in its routing table.
I hope this has been helpful!
Laz