S1. How do config errors made in OSPF vs BGP affect Internet operation?

Question 1

What is OSPF?

Answer 1

Open Shortest Path First (OSPF) is a routing protocol used within autonomous systems (eg a single organization’s network)

Question 2

What is BGP?

Answer 2

Borderline Gateway Protocol (BPG) is a routing protocol for exchanging routing information between autonomous systems

Question 3

What are the differences between OSPF and BGP?

Answer 3

OSPF is a link-state protocol, while BGP is a vector path protocol. OSPF is used within AS’s, BGP is used between AS’s. OSPF is an Interior Gateway Protocol (IGP), BGP is an Exterior Gateway Protocol (EGP)

Question 4

What are the effects of config errors in OSPF?

Answer 4

Suboptimal routing, routing loops, increased convergence time (ie network takes longer to stabilize when routers update their tables), security risks due to mismatched authentication settings

Question 5

What are the effects of config errors in BGP?

Answer 5

Routing instability, reachability issues, traffic blackholing (data loss due to data being sent to unreachable or inexistent routes), route leaks (network advertising routes it shouldn’t), security risks and increased costs due to inefficient routing as a result of route leaks, session establishment failures

Question 6

What is the difference in scale of impact between config errors in OSPF vs BGP?

Answer 6

OSPF config errors cause issues locally, in a single organization’s network. BGP config errors can cause issues globally, for millions of users, and have significant financial ramifications

Question 7

What are some examples of OSPF config errors?

Answer 7

Mismatched area IDs, incorrect network statements, mismatched subnet masks, authentication mismatch

Question 8

What are common causes of config errors?

Answer 8

Human error, lack of coordination, changes in network design, outdated or incomplete documentation, and complexity of network environments

Question 9

What is the direct consequence of OSPF config errors?

Answer 9

They prevent routers from forming adjacencies, which leads to loss of connectivity within the network

Question 10

What is the direct consequence of BGP config errors?

Answer 10

They prevent routers from establishing BGP sessions, leading to routing failures and potential network isolation, and lead to routes being blocked or unintentionally advertised, causing routing issues and potential security risks