CCDE 400-007: Which type of loop would be reduced by using OSPF LFA?

Table of Contents

Question
Answer
Explanation
Reference

Question

An engineer must design a network for a company that uses OSPF LFA to reduce loops. Which type of loop would be reduced by using this design?

A. DTP
B. micro loops
C. STP
D. REP

Answer

B. micro loops

Explanation

OSPF LFA reduces micro loops.

DTP is Dynamic Trunking Protocol, which is used to dynamically create trunks between switches. It does not reduce loops.
STP is Spanning Tree Protocol, which is a loop-avoidance protocol used in Ethernet networks. It reduces loops by blocking redundant links.
REP is Routing Engine Protection, which is a Cisco feature that protects against routing engine failures. It does not reduce loops.

OSPF LFA works by pre-computing a loop-free alternate path for each OSPF route. This path is a backup path that does not traverse the same link as the primary path. If the primary path fails, OSPF LFA can quickly switch to the backup path to avoid traffic loss.

Micro loops are loops that occur within a single OSPF area. They can be caused by redundant links between routers in the same area. OSPF LFA can reduce micro loops by pre-computing a loop-free alternate path for each OSPF route. This path is a backup path that does not traverse any of the links in the same area as the primary path.

Here is an example of how OSPF LFA can reduce micro loops. Consider a network with two routers, R1 and R2, in the same OSPF area. Router R1 has two links to Router R2, one via interface Ethernet0/0 and one via interface Ethernet0/1. Router R2 has two links to Router R1, one via interface Ethernet1/0 and one via interface Ethernet1/1.

If the link between Router R1 and Router R2 via interface Ethernet0/0 fails, OSPF LFA will automatically switch to the backup path, which is the link between Router R1 and Router R2 via interface Ethernet0/1. This will prevent a micro loop from occurring.

OSPF LFA is a powerful tool that can be used to reduce loops in OSPF networks. It is especially useful for reducing micro loops, which can be difficult to troubleshoot and can cause significant disruption to network traffic.

Reference

Cisco Certified Design Expert CCDE v3.0 400-007 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Cisco Certified Design Expert CCDE v3.0 400-007 exam and earn Cisco Certified Design Expert CCDE v3.0 400-007 certification.