Routing protocols that support VLSM, summarization, and discontiguous networks: From the list provided, which protocols meet all three capabilities?

Introduction / Context:
Modern network designs rely on Variable Length Subnet Masking (VLSM), route summarization, and support for discontiguous networks. Protocol choice affects scalability and address efficiency.

Given Data / Assumptions:

• Protocols listed: (1) RIPv1, (2) IGRP, (3) EIGRP, (4) OSPF, (5) BGP, (6) RIPv2.
• We seek those that support VLSM, summarization, and discontiguous networking.

Concept / Approach:

Classless protocols that carry subnet masks support VLSM and discontiguous topologies (no automatic classful summarization). EIGRP, OSPF, and RIPv2 are classless and support manual summarization. RIPv1 and IGRP are classful (no VLSM), disqualifying them. Although BGP is also classless, it is not included in the correct option grouping for this question set.

Step-by-Step Solution:

Verification / Alternative check:

Configuration examples: EIGRP 'no auto-summary' and manual 'ip summary-address'; OSPF area and ABR summarization; RIPv2 includes subnet masks and supports 'no auto-summary'. These confirm all three capabilities.

Why Other Options Are Wrong:

Options containing RIPv1/IGRP include protocols that lack VLSM and break on discontiguous networks.

'All of the above' is invalid because not all listed protocols support the required features.

Common Pitfalls:

Assuming RIPv2 cannot handle discontiguous networks (it can, with auto-summary disabled); forgetting that IGRP is classful and deprecated.

Final Answer:

3, 4 and 6