OSPF

[abdul.qadir5001]

Howto avoid OSPF routing loops. When i google it then i come to know that

"The loop avoidance is inherent in the SPF algorithm,which OSPF (as a link-state routing protocol) uses to calculate routes.This way, a tree is built for each router with itself as the root.Trees by definition do not have loops.Extensions to this tree exist only for load-balancing reasons."

Kinsly guide plz that i cannot understand it. Thanks

[Vishnu Vardhan S]

OSPF has inbuilt mechanism of loop prevention with the help of SPF algorithm it runs. 

Apart from that you have some features like :

The back bone area creates an one to one connection to all non backbone areas preventing a chance of loop

But what you have Area 0 connected to Area 1 and Area 2. Also there is a link between Area 1 and 2. 

In this condition a rule comes into play that an ABR will reject all the type 3 LSA's coming from the non backbone areas. 

Also when you have two ABR's in an are let it be R10 and R20 then both of them will reject any type 3 lsa's coming from each other.