What is the default redistribution OSPF cost?
Redistribution into OSPF uses the following defaults:
- BGP, use a default metric of 1.
- All other IGP sources use a default metric of 20.
Explain OSPF Virtual Link?
OSPF requires using a backbone area (area 0), with each area connecting to area 0 through an ABR. However, in some cases, the regular area might not have a convenient point of connection to the backbone area. In this case, OSPF uses the virtual link to connect that regular area to the backbone area virtually.
Explain OSPF Stub Area and different types of Stub Areas.
- Stub Area: Filter external routes (EIGRP/BGP) and a default route is injected into a stub area by ABR.
- Totally Stubby Area: Routers within the Totally Stubby Area receive only a single default route to reach external destinations, filter all other updates.
- Not-So-Stubby Areas: NSSA permits the injection of external routes, such as routes redistributed from other routing protocols or static routes, into the area while still summarizing them into a default route.
- Totally NSSA: In a Totally NSSA, external routes, including those redistributed from other routing protocols or static routes, are allowed to enter the area, but they are summarized into a default route.
How does OSPF calculate its metric or cost?
OSPF determines the best path to a destination using cost, which is based on interface bandwidth.
Can a router belong to more than one OSPF area?
A: Yes, a router can have interfaces in multiple OSPF areas.
Explanation: This is how Area Border Routers (ABRs) connect non-backbone areas to Area 0.
