IPv6 - Internet Protocol version 6

What is IPv6?

IPv6 stands for Internet Protocol version 6. It is the successor to IPv4, designed to solve the problem of IP address exhaustion. IPv6 uses 128-bit addresses, allowing for a vastly larger number of unique IP addresses compared to IPv4’s 32-bit system.

Why is IPv6 useful?

  • IPv4 addresses are running out due to the explosion of internet-connected devices.

  • It supports more efficient routing and better security features.

  • It enables end-to-end connectivity without the need for NAT (Network Address Translation).

  • It simplifies network configuration with auto-configuration capabilities.

How it works?

  • Device gets an IPv6 address — either via DHCPv6 or Stateless Address Autoconfiguration (SLAAC).

  • Packets are created with IPv6 headers — including source and destination IPv6 addresses.

  • Routers forward packets — based on the destination IPv6 address.

  • Target device receives data — and processes the packet if the address matches.

Where is IPv6 used?

  • Modern internet infrastructure — ISPs, cloud providers, and large enterprises are adopting IPv6.

  • Mobile networks — many cellular networks use IPv6 by default.

  • IoT devices — IPv6 supports the massive scale of connected devices.

  • Next-gen applications — that require direct, scalable, and secure communication.

Which OSI Layer does IPv6 operate at?

  • IPv6 operates at the Network Layer (Layer 3) of the OSI model.

  • It provides logical addressing and routing between devices across different networks.

  • It encapsulates data into packets and ensures they reach the correct destination.

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

Version & RFC Details

IPv6 Version

RFC Version

Year

Core Idea / Contribution

IPv6

RFC 1883

1995

Original specification of IPv6.

RFC 2460

1998

First major IPv6 specification; introduced 128-bit addressing, simplified headers, extension headers, flow labels.

RFC 4291

2006

Defines IPv6 addressing architecture including unicast, multicast, and anycast addresses.

RFC 4443

2006

Defines ICMPv6, the control messaging protocol for IPv6.

RFC 4861

2007

Specifies Neighbor Discovery Protocol (NDP) for IPv6.

RFC 4862

2007

Defines Stateless Address Autoconfiguration (SLAAC) for IPv6.

RFC 6106

2010

Adds DNS configuration options to Router Advertisements.

RFC 5952

2010

Defines a canonical textual representation format for IPv6 addresses.

RFC 8200

2017

Obsoletes RFC 2460; current standard for IPv6. Clarifies extension headers, flow labels, and updates terminology.

RFC 9386

2023

Provides updated status and deployment insights for IPv6.

  • Setup

  • Setup

IPv6 Packet

S.No

Protocol Packets

Description

Size(bytes)

1

IPv6

141

Header

41

Version

IP version (6 for IPv6)

1

Traffic Class

specifying the priority of the packet.

1

Flow Label

identifying flows of packets.

3

Payload Length

indicating the length of the payload.

2

Next Header

specifying the next level protocol (e.g., TCP, UDP).

1

Hop Limit

maximum number of hops the packet can take.

1

Source IP Address

IP address of the sender.

16

Destination IP Address

IP address of the receiver.

16

Data

actual payload carried by the IP packet.

variable(100)

IPv6 - Use Cases

S.no

Use Case

Description

1

Internet Communication

IPv6 provides a vastly larger address space (128-bit) to support the growing number of internet-connected devices.

2

Enterprise Networking

Used in modern LANs and WANs, especially in organizations transitioning from IPv4 to IPv6 for scalability and future-proofing.

3

Web Hosting & DNS

Websites and services are increasingly hosted with IPv6 addresses; DNS supports AAAA records for IPv6 resolution.

4

End-to-End Connectivity

Eliminates the need for NAT, enabling true peer-to-peer communication and simplifying network configurations.

5

VPN and Remote Access

IPv6 supports secure tunneling and remote access protocols, often coexisting with IPv4 in dual-stack environments.

6

IoT and Smart Devices

IPv6s vast address space allows unique addressing for billions of IoT devices, improving manageability and routing.

7

Stateless Address Autoconfiguration (SLAAC)

Devices can self-configure IP addresses without DHCP, simplifying network setup.

8

Multimedia and Real-Time Services

IPv6 supports efficient multicast and QoS features, enhancing performance for VoIP, video conferencing, and streaming.

IPv6 - Basic Features

S.no

Features

Description

1

128-bit Addressing

Vast address space, enabling trillions of unique IPs.

2

Simplified Header Structure

Fixed 40-byte header with optional extension headers for flexibility.

3

Multicast Support

Efficient one-to-many communication for services like streaming.

4

Stateless Address Autoconfiguration (SLAAC)

Devices can self-configure IPs using router advertisements.

5

Improved Security (IPsec)

Mandatory support for encryption and authentication at the IP layer.

6

Flow Label Field

Allows labeling of packets for special handling.

7

Extension Headers

Modular headers for routing, fragmentation, security, etc.

8

Hop Limit

Replaces IPv4s TTL; limits packet lifetime across routers.

9

Classless Addressing

No address classes (A, B, C); uses CIDR-like prefixing.

10

Efficient Routing

Aggregated prefixes and simplified headers improve routing performance.

128-bit Addressing - Testcases

Sl.no

Test Case

Description

Expected Result

1

Assign Valid IPv6 Address

Assign 2001:db8::1

Address accepted

2

Assign Invalid IPv6 Address

Assign 2001:db8::1:1:1::1

Address rejected

3

Assign Full 128-bit Address

Use all 8 segments

Address accepted

4

Assign Compressed Address

Use :: for zeros

Address accepted

5

Assign Loopback Address

::1

Packet routed locally

6

Assign Link-local Address

fe80::1

Used for local link communication

7

Assign Unique Local Address

fc00::/7

Used for internal networks

8

Assign Global Unicast Address

2000::/3

Routable on the internet

9

Assign Multicast Address

ff00::/8

Used for multicast traffic

10

Assign Reserved Address

::

Used as unspecified address

11

Assign IPv4-Mapped IPv6 Address

::ffff:192.0.2.128

Used for IPv4 compatibility

12

Assign IPv4-Compatible IPv6 Address

::192.0.2.128

Deprecated but accepted

13

Assign Address with Leading Zeros

2001:0db8::1

Address normalized

14

Assign Address with Uppercase Letters

2001:DB8::1

Address accepted case insensitive

15

Assign Address with Lowercase Letters

2001:db8::1

Address accepted

16

Assign Address with Embedded IPv4

::ffff:192.168.1.1

IPv4 mapped IPv6 address

17

Assign Address with Invalid Characters

2001:db8::g1

Address rejected

18

Assign Address with Too Many Segments

9 segments

Address rejected

19

Assign Address with Too Few Segments

6 segments without ::

Address rejected

20

Assign Address with Multiple ::

2001::db8::1

Address rejected

21

Assign Address with All Zeros

::

Used as unspecified address

22

Assign Address with All Ones

ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff

Valid, reserved

23

Assign Address with Prefix Length

2001:db8::/64

Network portion defined

24

Assign Address with /128 Prefix

Host-specific address

Used for loopback or point-to-point

25

Assign Address with /64 Prefix

Standard subnet size

Used in most networks

26

Assign Address with /48 Prefix

Site-level aggregation

Used by ISPs

27

Assign Address with /32 Prefix

Global routing prefix

Assigned to large organizations

28

Assign Address with /127 Prefix

Point-to-point links

Used in router-to-router links

29

Assign Address with /0 Prefix

Default route

Used in routing tables

30

Assign Address with SLAAC

Stateless autoconfiguration

Address generated automatically

31

Assign Address with DHCPv6

Stateful configuration

Address assigned by server

32

Assign Address with Privacy Extension

Temporary address

Used for outbound connections

33

Assign Address with Stable Interface ID

Based on MAC

Persistent address

34

Assign Address with Random Interface ID

Randomized

Enhances privacy

35

Assign Address with Duplicate Detection

DAD enabled

Duplicate address rejected

36

Assign Address with Manual Configuration

Static assignment

Address accepted

37

Assign Address with Multicast Scope

ff02::1

Link-local multicast

38

Assign Address with Site-local Scope

fec0::/10

Deprecated, not routable

39

Assign Address with Global Scope

2001::/16

Routable globally

40

Assign Address with Interface Index

fe80::1%eth0

Used for link-local routing

41

Assign Address with Routing Header

Used in packet

Routing header processed

42

Assign Address with Extension Headers

Fragmentation, security, etc.

Headers processed

43

Assign Address with ICMPv6

Ping to IPv6 address

Echo reply received

44

Assign Address with DNS AAAA Record

IPv6 DNS resolution

Address resolved

45

Assign Address with NAT64

IPv6 to IPv4 translation

Address mapped

46

Assign Address with Dual Stack

IPv4 and IPv6 coexist

Both addresses assigned

47

Assign Address with Firewall

IPv6 rules applied

Traffic filtered

48

Assign Address with ACL

IPv6 ACLs applied

Traffic permitted or denied

49

Assign Address with Routing Protocol

OSPFv3, BGP, etc.

Address advertised

50

Assign Address with Packet Capture

Wireshark or tcpdump

IPv6 address visible in capture

Simplified Header Structure - Testcases

S.no

Test Case

Description

Expected Result

1

Validate Fixed Header Size

IPv6 header is 40 bytes

Header accepted

2

No Header Checksum

No checksum field

Router does not perform checksum validation

3

No Fragmentation in Header

No fragmentation fields

Fragmentation handled via extension header

4

No Options Field

No variable-length options

Simplified parsing

5

Validate Version Field

Version = 6

Packet accepted

6

Invalid Version Field

Version ? 6

Packet dropped

7

Validate Traffic Class Field

QoS marking present

Used for traffic prioritization

8

Validate Flow Label Field

Flow label set

Used for flow identification

9

Validate Payload Length Field

Correct length

Packet accepted

10

Invalid Payload Length

Length mismatch

Packet dropped

11

Validate Next Header Field

Indicates upper-layer protocol

Packet routed accordingly

12

Unknown Next Header Value

Unsupported protocol

Packet dropped

13

Validate Hop Limit Field

TTL equivalent

Decremented per hop

14

Hop Limit = 0

TTL expired

Packet dropped

15

Validate Source Address

Valid 128-bit address

Packet accepted

16

Invalid Source Address

Malformed address

Packet dropped

17

Validate Destination Address

Valid 128-bit address

Packet routed

18

Invalid Destination Address

Malformed address

Packet dropped

19

Header with Extension Headers

Next Header points to extension

Extension processed

20

Header with No Extension Headers

Next Header = TCP/UDP

Packet routed directly

21

Header with Routing Extension

Routing header present

Intermediate nodes processed

22

Header with Fragment Extension

Fragmentation handled externally

Reassembly at destination

23

Header with Authentication Header

AH present

Packet authenticated

24

Header with ESP

Encrypted payload

Decryption required

25

Header with Hop-by-Hop Options

Special processing at each hop

Options processed

26

Header with Destination Options

Options processed at destination

Packet accepted

27

Header with Jumbo Payload Option

Payload > 65535 bytes

Jumbo payload handled

28

Header with Mobility Header

Mobile IPv6 support

Mobility functions triggered

29

Header with No Padding

No alignment needed

Packet accepted

30

Header with Upper-Layer Protocol = TCP

Next Header = 6

Routed to TCP stack

31

Header with Upper-Layer Protocol = UDP

Next Header = 17

Routed to UDP stack

32

Header with Upper-Layer Protocol = ICMPv6

Next Header = 58

Routed to ICMPv6 handler

33

Header with Upper-Layer Protocol = OSPF

Next Header = 89

Routed to OSPFv3

34

Header with Upper-Layer Protocol = GRE

Next Header = 47

Routed to GRE handler

35

Header with Upper-Layer Protocol = ESP

Next Header = 50

Routed to IPsec stack

36

Header with Upper-Layer Protocol = AH

Next Header = 51

Routed to IPsec stack

37

Header with Invalid Flow Label

Non-zero but unused

Packet still accepted

38

Header with Zero Flow Label

Default behavior

Packet accepted

39

Header with Random Flow Label

Used for load balancing

Packet accepted

40

Header with Traffic Class = EF

Expedited forwarding

Packet prioritized

41

Header with Traffic Class = AF

Assured forwarding

Packet prioritized accordingly

42

Header with Traffic Class = CS

Class selector

Packet handled per class

43

Header with Extension Header Chain

Multiple extensions

All processed in order

44

Header with Malformed Extension Chain

Invalid order or loop

Packet dropped

45

Header with Unknown Extension Header

Unrecognized type

Packet dropped or skipped

46

Header with Extension Header Length Error

Length mismatch

Packet dropped

47

Header with No Upper-Layer Protocol

Next Header = 59 (No Next Header)

Payload ignored

48

Header with ICMPv6 Error

Error message generated

Sent to source

49

Header with Multicast Destination

ff00::/8

Packet delivered to group

50

Header with Unicast Destination

2001::1

Packet routed normally

Multicast Support - Testcases

Multicast Support - Test Cases

#

Test Case

Description

Expected Result

1

Send to All-Nodes Multicast

Destination = ff02::1

All nodes on local link receive

2

Send to All-Routers Multicast

Destination = ff02::2

All routers on local link receive

3

Send to Solicited-Node Multicast

Destination = ff02::1:ffxx:xxxx

Only matching node receives

4

Join Multicast Group

Host joins group via MLD

Group membership recorded

5

Leave Multicast Group

Host leaves group

Group membership updated

6

Use MLDv1

Host uses MLDv1

Basic group join/leave supported

7

Use MLDv2

Host uses MLDv2

Source filtering supported

8

Send ICMPv6 Router Advertisement

Sent to ff02::1

All nodes receive

9

Send ICMPv6 Router Solicitation

Sent to ff02::2

Routers respond

10

Send ICMPv6 Neighbor Solicitation

Sent to solicited-node address

Target node responds

11

Send ICMPv6 Neighbor Advertisement

Sent to ff02::1

All nodes update cache

12

Use DHCPv6 Multicast

Sent to ff02::1:2

DHCPv6 servers respond

13

Use Multicast DNS (mDNS)

Sent to ff02::fb

Local name resolution

14

Use LLMNR

Sent to ff02::1:3

Local name resolution

15

Use RIPng

Sent to ff02::9

RIP routers receive updates

16

Use OSPFv3

Sent to ff02::5 and ff02::6

OSPF routers receive messages

17

Use PIM

Sent to ff02::d

PIM routers receive messages

18

Use NTP Multicast

Sent to multicast group

Time sync achieved

19

Use SNMP Trap Multicast

Sent to SNMP listeners

Trap received

20

Use SSDP over IPv6

Sent to ff02::c

Devices discoverable

21

Use Multicast for Streaming

Video sent to group

Only members receive

22

Use Multicast for Software Updates

Update sent to group

Efficient delivery

23

Use Multicast for IoT Devices

Sensor data multicast

All subscribers receive

24

Use Multicast for Classroom

Lecture stream multicast

Students receive stream

25

Use Multicast for Gaming

Game state multicast

All players updated

26

Use Multicast for CDN

Content distributed via multicast

Edge nodes receive data

27

Use Multicast for Backup

Data replicated via multicast

All nodes updated

28

Use Multicast for Logging

Logs sent to multicast group

Central server receives

29

Use Multicast for Alerting

Alerts sent to group

All listeners notified

30

Use Multicast with VLAN

Scoped to VLAN

Only VLAN members receive

31

Use Multicast with QoS

DSCP marked packets

Prioritized delivery

32

Use Multicast with ACL

ACL allows multicast

Packet forwarded

33

Use Multicast with Firewall

Firewall permits group

Packet allowed

34

Use Multicast with NAT64

Translated to IPv4 multicast

Packet routed

35

Use Multicast with VPN

Multicast tunneled

Packet delivered

36

Use Multicast with Wireless

Sent over Wi-Fi

All clients receive

37

Use Multicast with Ethernet

Switch floods to group members

Efficient delivery

38

Use Multicast with MLD Snooping

Switch tracks group members

Traffic limited to members

39

Use Multicast with Logging

Multicast events logged

Entries recorded

40

Use Multicast with Monitoring

Multicast traffic captured

Visible in packet sniffer

41

Use Multicast with IPv6 Anycast

Anycast not used

Packet not delivered

42

Use Multicast with IPv4 Stack

Not supported

Packet dropped

43

Use Multicast with Extension Headers

Routing or fragmentation

Packet processed

44

Use Multicast with Jumbo Payload

Payload > 65535 bytes

Delivered if supported

45

Use Multicast with Fragmentation

Packet fragmented

Reassembled at receiver

46

Use Multicast with Source Filtering

MLDv2 include/exclude

Source-based delivery

47

Use Multicast with Duplicate Address Detection

NS sent to solicited-node

Conflict detected

48

Use Multicast with Privacy Extensions

Temporary address used

Multicast still functional

49

Use Multicast with Static Routes

Route to group defined

Packet forwarded

50

Use Multicast with Dynamic Routing

Route learned via protocol

Packet routed correctly

Stateless Address Autoconfiguration (SLAAC) - Testcases

Stateless Address Autoconfiguration (SLAAC) - Test Cases

#

Test Case

Description

Expected Result

1

SLAAC Enabled Interface

Interface configured for SLAAC

IPv6 address auto-configured

2

SLAAC Disabled Interface

SLAAC disabled

No address auto-configured

3

Receive Router Advertisement (RA)

RA received with A-flag set

Host configures address

4

RA with A-flag Cleared

Autonomous flag not set

Host does not configure address

5

RA with Prefix Information

Valid prefix advertised

Host uses prefix for address

6

RA with Invalid Prefix

Prefix length ? /64

Host ignores prefix

7

Generate Interface ID from MAC

EUI-64 format used

Address generated correctly

8

Generate Interface ID Randomly

Privacy extension enabled

Temporary address created

9

Duplicate Address Detection (DAD) Success

No conflict

Address assigned

10

DAD Failure

Duplicate detected

Address not assigned

11

Multiple RAs Received

Multiple prefixes advertised

Multiple addresses configured

12

RA with Lifetime Expired

Prefix lifetime = 0

Address deprecated or removed

13

RA with Valid Lifetime

Prefix lifetime > 0

Address remains valid

14

RA with On-Link Flag

L-flag set

Prefix added to routing table

15

RA with No On-Link Flag

L-flag cleared

Prefix not added to routing table

16

RA with M-flag Set

Managed flag set

Host may use DHCPv6

17

RA with O-flag Set

Other config flag set

Host may use DHCPv6 for DNS

18

SLAAC with Static DNS

DNS manually configured

SLAAC address used with static DNS

19

SLAAC with RDNSS Option

DNS provided in RA

Host configures DNS

20

SLAAC with No RDNSS

No DNS in RA

DNS not auto-configured

21

SLAAC with Link-Local RA

RA from link-local router

Address configured

22

SLAAC with Global RA

RA from global address

Address configured

23

SLAAC with Multicast RA

RA sent to ff02::1

All nodes receive

24

SLAAC with Unicast RA

RA sent directly

Target node configures address

25

SLAAC with VLAN

RA received on VLAN

Address configured on VLAN interface

26

SLAAC with Trunk Port

RA received on tagged VLAN

Address configured correctly

27

SLAAC with Access Port

RA received on untagged VLAN

Address configured correctly

28

SLAAC with Wireless Interface

RA received over Wi-Fi

Address configured

29

SLAAC with Ethernet Interface

RA received over Ethernet

Address configured

30

SLAAC with VPN Interface

RA received over tunnel

Address configured

31

SLAAC with Firewall

RA allowed

Address configured

32

SLAAC Blocked by Firewall

RA blocked

No address configured

33

SLAAC with ACL

RA permitted

Address configured

34

SLAAC with ACL Deny

RA denied

No address configured

35

SLAAC with Logging Enabled

RA processed

Event logged

36

SLAAC with Packet Capture

RA and NS/NA visible

SLAAC process observable

37

SLAAC with Host Reboot

Host reboots

Address reconfigured

38

SLAAC with Router Reboot

Router reboots

RA resumes after boot

39

SLAAC with Multiple Interfaces

RA received on multiple interfaces

Address configured per interface

40

SLAAC with Interface Down

Interface disabled

No address configured

41

SLAAC with Interface Up

Interface enabled

Address configured

42

SLAAC with Manual Address

Static address present

SLAAC address coexists

43

SLAAC with DHCPv6

Both enabled

SLAAC configures address, DHCPv6 configures DNS

44

SLAAC with Privacy Extensions

Temporary address created

Used for outbound connections

45

SLAAC with Stable Interface ID

Address remains consistent

Persistent address

46

SLAAC with Short RA Interval

Frequent RAs

Address refreshed often

47

SLAAC with Long RA Interval

Infrequent RAs

Address remains valid

48

SLAAC with Expired Prefix

Prefix lifetime = 0

Address deprecated

49

SLAAC with Multiple Routers

Multiple RAs

Host selects preferred prefix

50

SLAAC with No RA

No router advertisement

No address configured

Improved Security - Testcases

Improved Security (IPsec) - Test Cases

#

Test Case

Description

Expected Result

1

Enable IPsec on IPv6 Interface

IPsec enabled

Interface accepts secure traffic

2

Disable IPsec on IPv6 Interface

IPsec disabled

Traffic not encrypted

3

Configure IPsec Transport Mode

Transport mode set

Payload encrypted, header visible

4

Configure IPsec Tunnel Mode

Tunnel mode set

Entire packet encrypted

5

Use Authentication Header (AH)

AH applied

Packet integrity verified

6

Use Encapsulating Security Payload (ESP)

ESP applied

Packet encrypted and authenticated

7

Use AH with IPv6

AH header inserted

Packet integrity protected

8

Use ESP with IPv6

ESP header inserted

Payload encrypted

9

Use AH + ESP

Both headers used

Full protection applied

10

Use Manual Keying

Static keys configured

Secure communication established

11

Use IKEv2 for Key Exchange

IKEv2 negotiation

SA established dynamically

12

Use IPsec with IPv6 Multicast

Multicast traffic secured

Group keying required

13

Use IPsec with IPv6 Unicast

Unicast traffic secured

Peer-to-peer encryption

14

Use IPsec with IPv6 Anycast

Anycast not supported

Packet dropped or ignored

15

Use IPsec with IPv6 Link-Local

Link-local traffic secured

Communication encrypted

16

Use IPsec with IPv6 Global Address

Global traffic secured

End-to-end encryption

17

Use IPsec with IPv6 Unique Local Address

ULA traffic secured

Internal traffic encrypted

18

Use IPsec with Fragmented Packet

Packet fragmented

Reassembled before decryption

19

Use IPsec with Jumbo Payload

Large packet encrypted

Delivered securely

20

Use IPsec with Extension Headers

Headers preserved

IPsec applied correctly

21

Use IPsec with Routing Header

Routing header encrypted

Packet routed securely

22

Use IPsec with Hop-by-Hop Header

Header processed

Packet integrity maintained

23

Use IPsec with ICMPv6

ICMPv6 messages secured

Echo request/reply encrypted

24

Use IPsec with TCP

TCP session encrypted

Data protected

25

Use IPsec with UDP

UDP datagram encrypted

Data protected

26

Use IPsec with DNS over IPv6

DNS queries encrypted

Privacy ensured

27

Use IPsec with NTP

Time sync secured

NTP packets encrypted

28

Use IPsec with SNMP

SNMP traps encrypted

Management traffic secured

29

Use IPsec with Routing Protocols

OSPFv3, RIPng secured

Routing updates protected

30

Use IPsec with SLAAC

RA/RS messages secured

Autoconfiguration protected

31

Use IPsec with DHCPv6

DHCPv6 messages encrypted

Address assignment secured

32

Use IPsec with MLD

Multicast group joins secured

MLD messages protected

33

Use IPsec with VPN over IPv6

Tunnel established

Secure remote access

34

Use IPsec with IPv6 over IPsec Tunnel

IPv6-in-IPv6 over IPsec

Double encapsulation supported

35

Use IPsec with NAT-T

NAT traversal enabled

IPsec works through NAT

36

Use IPsec with Firewall

IPsec traffic allowed

Policy permits secure traffic

37

Use IPsec with ACL

ACL matches ESP/AH

Traffic filtered correctly

38

Use IPsec with QoS

DSCP preserved

Traffic prioritized

39

Use IPsec with Logging

Security events logged

IPsec activity recorded

40

Use IPsec with Monitoring

IPsec sessions monitored

Status visible in tools

41

Use IPsec with Packet Capture

ESP/AH visible

Payload encrypted

42

Use IPsec with Replay Protection

Anti-replay enabled

Duplicate packets dropped

43

Use IPsec with Key Lifetime Expiry

SA expires

Re-keying triggered

44

Use IPsec with Invalid SA

No matching SA

Packet dropped

45

Use IPsec with Invalid SPI

SPI not recognized

Packet dropped

46

Use IPsec with Authentication Failure

Invalid HMAC

Packet dropped

47

Use IPsec with Encryption Failure

Decryption fails

Packet dropped

48

Use IPsec with Peer Unreachable

No response

SA not established

49

Use IPsec with Host Reboot

Host restarts

SA re-established

50

Use IPsec with Router Reboot

Router restarts

Tunnel re-established

Flow Label Field - Testcases

Flow Label Field - Test Cases

#

Test Case

Description

Expected Result

1

Flow Label = 0

Default value

Treated as no special handling

2

Flow Label ? 0

Non-zero value

Flow-specific treatment applied

3

Flow Label with TCP

TCP session assigned flow label

Packets grouped by flow

4

Flow Label with UDP

UDP stream assigned flow label

Packets grouped by flow

5

Flow Label with ICMPv6

ICMPv6 echo request

Flow label ignored or set to 0

6

Flow Label with SCTP

SCTP stream assigned label

Flow identified

7

Flow Label with Fragmented Packet

All fragments share same label

Reassembled correctly

8

Flow Label with Jumbo Payload

Large packet with label

Handled as single flow

9

Flow Label with Extension Headers

Label preserved

Headers processed normally

10

Flow Label with Routing Header

Label used for flow routing

Packet routed accordingly

11

Flow Label with Hop-by-Hop Header

Label processed at each hop

Packet treated per flow

12

Flow Label with ESP

Encrypted payload

Label visible, payload encrypted

13

Flow Label with AH

Authenticated header

Label integrity protected

14

Flow Label with QoS Policy

Label used for QoS classification

Traffic prioritized

15

Flow Label with Traffic Shaping

Label used for shaping

Bandwidth managed

16

Flow Label with Load Balancer

Label used for hashing

Flow consistency maintained

17

Flow Label with Firewall

Label used in rules

Traffic filtered accordingly

18

Flow Label with ACL

ACL matches flow label

Packet permitted or denied

19

Flow Label with Logging

Label logged

Entry recorded

20

Flow Label with Monitoring

Label visible in capture

Flow identified

21

Flow Label with Packet Sniffer

Wireshark shows label

Field decoded

22

Flow Label with Router

Router uses label for fast path

Packet forwarded efficiently

23

Flow Label with Switch

Label ignored

Layer 2 device forwards normally

24

Flow Label with NAT64

Label preserved

IPv6-to-IPv4 translation occurs

25

Flow Label with VPN

Label preserved through tunnel

Flow maintained

26

Flow Label with MPLS

Label mapped to MPLS label

Traffic engineered

27

Flow Label with SRv6

Segment routing uses label

Path optimized

28

Flow Label with Mobile IPv6

Label used for mobility flow

Session continuity maintained

29

Flow Label with DNS

Label not used

DNS traffic treated normally

30

Flow Label with NTP

Label not used

Time sync unaffected

31

Flow Label with DHCPv6

Label not used

Address assignment unaffected

32

Flow Label with Multicast

Label ignored

Multicast traffic not flow-specific

33

Flow Label with Anycast

Label ignored

Closest node responds

34

Flow Label with SLAAC

Label not used

Address auto-configured

35

Flow Label with Privacy Extensions

Label used with temporary address

Flow maintained

36

Flow Label with Stable Interface ID

Label reused

Flow consistency ensured

37

Flow Label with Replay Attack

Label reused maliciously

Packet dropped or logged

38

Flow Label with Random Generation

Label randomly assigned

Flow uniqueness ensured

39

Flow Label with Hash-Based Assignment

Label derived from 5-tuple

Consistent flow ID

40

Flow Label with Manual Configuration

Admin sets label

Custom flow control

41

Flow Label with Zero Compression

Label = 0

No flow-specific treatment

42

Flow Label with Duplicate Value

Same label for different flows

Risk of misclassification

43

Flow Label with Expired Flow

Flow ends, label reused

New flow established

44

Flow Label with High Entropy

Randomized label

Improves load distribution

45

Flow Label with Low Entropy

Sequential label

May cause imbalance

46

Flow Label with ICMPv6 Error

Error message includes label

Helps trace flow

47

Flow Label with Traceroute

Label preserved

Path traced per flow

48

Flow Label with Path MTU Discovery

Label not used

PMTUD functions normally

49

Flow Label with Congestion Control

Label used for flow fairness

Traffic balanced

50

Flow Label with Application Tagging

App sets label

Enables app-aware routing

Extension Headers - Testcases

Extension Headers - Test Cases

#

Test Case

Description

Expected Result

1

No Extension Header

Only base header used

Packet processed normally

2

Hop-by-Hop Options Header Present

First extension header

Processed by each router

3

Routing Header Present

Specifies intermediate nodes

Packet routed accordingly

4

Fragment Header Present

Packet fragmented

Reassembled at destination

5

Destination Options Header Present

Options for destination

Processed only by destination

6

Authentication Header (AH) Present

IPsec authentication

Packet integrity verified

7

Encapsulating Security Payload (ESP) Present

IPsec encryption

Payload decrypted

8

Mobility Header Present

Mobile IPv6 support

Mobility functions triggered

9

Unknown Extension Header

Unrecognized type

Packet dropped or skipped

10

Extension Header Order Valid

Correct sequence

Packet accepted

11

Extension Header Order Invalid

Incorrect sequence

Packet dropped

12

Multiple Extension Headers

Chain of headers

All processed in order

13

Extension Header Length Valid

Proper length field

Header parsed correctly

14

Extension Header Length Invalid

Incorrect length

Packet dropped

15

Hop-by-Hop Header with Router Alert

Special processing

Packet inspected

16

Hop-by-Hop Header with Jumbo Payload Option

Payload > 65535 bytes

Packet accepted

17

Routing Header Type 0

Deprecated

Packet dropped or ignored

18

Routing Header Type 2

Mobile IPv6

Packet routed to home agent

19

Fragment Header with Offset = 0

First fragment

Reassembly begins

20

Fragment Header with MF = 1

More fragments follow

Await reassembly

21

Fragment Header with MF = 0

Last fragment

Reassembly completes

22

Fragment Header with Overlapping Fragments

Malformed fragments

Packet dropped

23

Fragment Header with Duplicate Fragments

Redundant data

Handled gracefully

24

AH with Valid Authentication

HMAC verified

Packet accepted

25

AH with Invalid Authentication

HMAC mismatch

Packet dropped

26

ESP with Valid Encryption

Payload decrypted

Packet accepted

27

ESP with Invalid Encryption

Decryption fails

Packet dropped

28

Destination Options with Pad1

Single-byte padding

Packet accepted

29

Destination Options with PadN

Multi-byte padding

Packet accepted

30

Destination Options with Unknown Option

Unrecognized option

Action based on option type

31

Extension Header with Next Header = TCP

TCP payload follows

Routed to TCP stack

32

Extension Header with Next Header = UDP

UDP payload follows

Routed to UDP stack

33

Extension Header with Next Header = ICMPv6

ICMPv6 follows

Routed to ICMPv6 handler

34

Extension Header with Next Header = No Next Header (59)

No upper-layer protocol

Payload ignored

35

Extension Header with Invalid Next Header

Unknown protocol

Packet dropped

36

Extension Header with Loop

Header points to itself

Packet dropped

37

Extension Header with Excessive Chain

Too many headers

Packet dropped

38

Extension Header with Truncated Data

Incomplete header

Packet dropped

39

Extension Header with Malformed Option

Invalid format

Packet dropped

40

Extension Header with Duplicate Types

Same header repeated

Handled per RFC rules

41

Extension Header with Logging Enabled

Headers logged

Entry recorded

42

Extension Header with Packet Capture

Headers visible in capture

Analyzed by tools

43

Extension Header with Firewall

Headers inspected

Packet allowed or blocked

44

Extension Header with ACL

ACL matches header type

Packet filtered

45

Extension Header with QoS

Headers preserved

Traffic prioritized

46

Extension Header with Router Reboot

Router processes headers

Packet forwarded

47

Extension Header with Host Reboot

Host reprocesses headers

Packet accepted

48

Extension Header with VPN

Headers encapsulated

Tunnel endpoint processes

49

Extension Header with NAT64

Headers preserved

Translated if supported

50

Extension Header with SRv6

Segment Routing Header

Path-based forwarding applied

Hop Limit - Testcases

Hop Limit - Test Cases

#

Test Case

Description

Expected Result

1

Hop Limit = 0

Packet with Hop Limit set to 0

Packet is dropped immediately

2

Hop Limit = 1

Packet with Hop Limit set to 1

Packet is forwarded once, then dropped

3

Hop Limit = 2

Packet with Hop Limit set to 2

Packet is forwarded twice, then dropped

4

Hop Limit = 255

Max Hop Limit value

Packet can traverse up to 255 hops

5

Hop Limit decrements by 1

Each router decrements Hop Limit

Hop Limit reduces by 1 per hop

6

Hop Limit not decremented

Router fails to decrement

Packet loops indefinitely (error)

7

Hop Limit = 1 at destination

Packet reaches destination with HL=1

Packet is accepted

8

Hop Limit = 1 at intermediate

Packet dropped at intermediate router

ICMPv6 Time Exceeded sent

9

Hop Limit = 0 at source

Source sends with HL=0

Packet dropped at source

10

Hop Limit = 128

Common default value

Packet traverses up to 128 hops

11

Hop Limit = 64

Another common default

Packet traverses up to 64 hops

12

Hop Limit = 10

Short-lived packet

Packet dropped after 10 hops

13

Hop Limit = 1 with traceroute

Used for hop discovery

ICMPv6 Time Exceeded returned

14

Hop Limit = 2 with traceroute

Used for second hop discovery

ICMPv6 Time Exceeded returned

15

Hop Limit = 255 with traceroute

Used to detect spoofing

Packet reaches destination

16

Hop Limit = 255, spoofed

Spoofed packet with HL=255

Packet dropped if not from local

17

Hop Limit = 1, loop test

Loop detection test

Packet dropped in loop

18

Hop Limit = 0, loop test

Loop detection test

Packet dropped immediately

19

Hop Limit = 5, 6 routers

Packet dropped at 6th router

ICMPv6 Time Exceeded sent

20

Hop Limit = 6, 6 routers

Packet reaches destination

Packet accepted

21

Hop Limit = 1, firewall

Firewall blocks low HL

Packet dropped

22

Hop Limit = 255, firewall

Firewall allows high HL

Packet forwarded

23

Hop Limit = 0, multicast

Multicast packet with HL=0

Packet dropped

24

Hop Limit = 1, multicast

Multicast packet with HL=1

Packet reaches local nodes

25

Hop Limit = 255, multicast

Multicast packet with HL=255

Packet reaches all nodes

26

Hop Limit = 1, ICMPv6

ICMPv6 error with HL=1

Packet dropped

27

Hop Limit = 255, ICMPv6

ICMPv6 error with HL=255

Packet reaches destination

28

Hop Limit = 1, ping

Ping with HL=1

First hop replies with ICMPv6

29

Hop Limit = 64, ping

Ping with HL=64

Packet reaches destination

30

Hop Limit = 0, ping

Ping with HL=0

Packet dropped

31

Hop Limit = 1, router test

Test router decrement

HL becomes 0, packet dropped

32

Hop Limit = 2, router test

HL becomes 1, then 0

Packet dropped at second router

33

Hop Limit = 255, loop test

Loop with max HL

Packet loops 255 times then dropped

34

Hop Limit = 1, NAT64

NAT64 translation with HL=1

Packet dropped

35

Hop Limit = 2, NAT64

NAT64 translation with HL=2

Packet forwarded once

36

Hop Limit = 1, DNS64

DNS64 response with HL=1

Packet dropped

37

Hop Limit = 64, DNS64

DNS64 response with HL=64

Packet accepted

38

Hop Limit = 1, VPN tunnel

VPN tunnel with HL=1

Packet dropped at tunnel entry

39

Hop Limit = 2, VPN tunnel

VPN tunnel with HL=2

Packet reaches tunnel exit

40

Hop Limit = 255, VPN tunnel

VPN tunnel with HL=255

Packet reaches destination

41

Hop Limit = 1, mobile IPv6

Mobile node sends with HL=1

Packet dropped

42

Hop Limit = 64, mobile IPv6

Mobile node sends with HL=64

Packet accepted

43

Hop Limit = 1, segment routing

Segment routing with HL=1

Packet dropped at first segment

44

Hop Limit = 3, segment routing

Packet reaches third segment

Packet dropped

45

Hop Limit = 5, segment routing

Packet reaches destination

Packet accepted

46

Hop Limit = 1, SRv6

SRv6 packet with HL=1

Dropped at first segment

47

Hop Limit = 2, SRv6

SRv6 packet with HL=2

Dropped at second segment

48

Hop Limit = 3, SRv6

SRv6 packet with HL=3

Reaches third segment

49

Hop Limit = 255, SRv6

SRv6 packet with HL=255

Reaches destination

50

Hop Limit = 0, security test

Test for HL=0 attack

Packet dropped, alert generated

Classless Addressing - Testcases

Classless Addressing - Test Cases

#

Test Case

Description

Expected Result

1

/128 address

Single host address

Only one device can use this address

2

/64 address

Standard subnet size

Supports 2^64 host addresses

3

/48 address

Site-level aggregation

Allows 65,536 /64 subnets

4

/32 address

ISP-level allocation

ISP can assign multiple /48s

5

/56 address

Customer site allocation

Allows 256 /64 subnets

6

/96 address

IPv4-mapped IPv6

Used for IPv4 compatibility

7

/127 address

Point-to-point link

Only two addresses usable

8

/126 address

Small subnet

Four addresses, two usable

9

/120 address

Very small subnet

256 addresses

10

/0 address

Default route

Matches all IPv6 addresses

11

/64 subnetting

Subnetting a /48 into /64s

65,536 subnets created

12

/56 subnetting

Subnetting a /48 into /56s

256 subnets created

13

/64 to /128

Assigning host address

Host gets unique address

14

/64 to /127

Assigning point-to-point

Two hosts can communicate

15

Invalid prefix /129

Prefix length > 128

Error: Invalid prefix

16

Overlapping prefixes

Two subnets overlap

Routing conflict

17

Non-overlapping prefixes

Proper subnetting

No conflict

18

Aggregation of /64s

Combine into /48

Route summarization

19

Aggregation of /56s

Combine into /32

ISP-level summarization

20

Assigning /64 to LAN

Standard practice

All devices auto-configure

21

Assigning /128 to host

Static assignment

Host gets fixed address

22

Assigning /127 to link

Point-to-point link

Efficient address use

23

Assigning /126 to link

Legacy point-to-point

Four addresses used

24

Assigning /96 to NAT64

IPv4/IPv6 translation

IPv4-mapped IPv6 works

25

Assigning /48 to enterprise

Large network

Multiple subnets supported

26

Assigning /56 to home user

Home network

Multiple LANs supported

27

Assigning /32 to ISP

ISP allocation

Multiple customers supported

28

Assigning /64 to loopback

Loopback interface

Unique address

29

Assigning /128 to loopback

Loopback with /128

Valid configuration

30

Assigning /64 to WAN

WAN interface

Valid configuration

31

Assigning /64 to VPN

VPN tunnel

Tunnel endpoints configured

32

Assigning /64 to VLAN

VLAN interface

Each VLAN gets unique subnet

33

Assigning /64 to wireless

Wireless LAN

Devices auto-configure

34

Assigning /64 to DMZ

DMZ network

Isolated subnet

35

Assigning /64 to server farm

Server subnet

Scalable addressing

36

Assigning /64 to IoT

IoT network

Supports many devices

37

Assigning /64 to cloud

Cloud subnet

Elastic addressing

38

Assigning /64 to container

Container network

Unique subnet per container

39

Assigning /64 to hypervisor

Virtual machines

Each VM gets address

40

Assigning /64 to SDN

Software-defined network

Programmable addressing

41

Assigning /64 to edge device

Edge computing

Local subnet

42

Assigning /64 to mobile network

5G/4G subnet

Mobile devices supported

43

Assigning /64 to satellite

Satellite link

IPv6 over satellite

44

Assigning /64 to mesh network

IoT mesh

Devices auto-configure

45

Assigning /64 to smart grid

Utility network

Smart meters addressed

46

Assigning /64 to SCADA

Industrial control

Secure addressing

47

Assigning /64 to testbed

Lab network

Isolated testing

48

Assigning /64 to research

Research subnet

Experimental addressing

49

Assigning /64 to education

Campus network

Multiple departments

50

Assigning /64 to public Wi-Fi

Guest network

Temporary addressing

Efficient Routing - Testcases

Efficient Routing - Test Cases

#

Test Case

Description

Expected Result

1

Longest Prefix Match

Router selects route with longest prefix

Packet forwarded via most specific route

2

Aggregated Route /32

ISP aggregates multiple /48s into /32

Reduces routing table size

3

Aggregated Route /48

Enterprise aggregates /64s into /48

Simplifies internal routing

4

Default Route ::/0

Packet with no specific match

Forwarded to default gateway

5

Static Route Configuration

Manually configured route

Packet follows static path

6

Dynamic Routing Protocol

OSPFv3 or BGPv6 used

Routes updated dynamically

7

Route Summarization

Summarize multiple routes

Reduces routing overhead

8

Route Redistribution

Between OSPFv3 and BGPv6

Routes shared across protocols

9

Equal-Cost Multi-Path (ECMP)

Multiple equal-cost routes

Load balanced forwarding

10

Unequal-Cost Multi-Path

Routes with different costs

Best path selected

11

Loop Prevention

Routing loop detected

Packet dropped or rerouted

12

Hop-by-Hop Header

Special routing instructions

Routers process header

13

Source Routing (deprecated)

Source specifies route

Not supported in modern IPv6

14

Segment Routing (SRv6)

Routing via segments

Packet follows segment list

15

Fast Reroute

Link failure recovery

Alternate path used instantly

16

Route Flapping

Unstable route

Route dampened or suppressed

17

Route Convergence

Network change occurs

Routing table updated quickly

18

Route Filtering

Block specific prefixes

Unwanted routes not installed

19

Route Preference

Administrative distance used

Most preferred route selected

20

Route Metric

Cost-based selection

Lowest metric route chosen

21

Link-State Routing

OSPFv3 builds topology

Efficient path computation

22

Distance Vector Routing

RIPng used

Simple but less efficient

23

BGPv6 Peering

External routing

Routes exchanged between ASes

24

BGPv6 Aggregation

Prefix aggregation in BGP

Reduces global table size

25

BGPv6 Filtering

Prefix-lists applied

Controls route advertisement

26

BGPv6 Communities

Tagging routes

Policy-based routing decisions

27

Route Advertisement

RA messages in SLAAC

Hosts learn default gateway

28

Route Lifetime

RA route expires

Host removes route

29

Multicast Routing

Efficient group delivery

Uses shortest path tree

30

Anycast Routing

Nearest node responds

Fast and efficient service

31

Mobile IPv6 Routing

Mobile node changes location

Route optimized via home agent

32

Route Optimization

Mobile IPv6 direct routing

Avoids triangle routing

33

Tunneling Efficiency

IPv6 over IPv4 tunnel

Adds overhead, less efficient

34

Native IPv6 Routing

No tunneling

Most efficient path

35

Dual Stack Routing

IPv4 and IPv6 coexist

IPv6 preferred if available

36

Policy-Based Routing

Route based on policy

Custom forwarding decisions

37

Traffic Engineering

SRv6 or MPLS used

Optimized path for traffic type

38

Load Balancing

Across multiple links

Improves throughput

39

Route Blackholing

Drop specific traffic

Prevents DDoS or misuse

40

Route Injection

Inject route into protocol

Adds new path dynamically

41

Route Leak Detection

BGP route leak occurs

Detected and mitigated

42

Route Hijack Detection

Malicious route advertised

Alert triggered

43

IPv6 Prefix Delegation

DHCPv6-PD assigns prefixes

Efficient subnetting

44

Recursive Route Lookup

Next-hop lookup required

Final route determined

45

Loopback Routing

::1 used for testing

Packet stays on local host

46

Blackhole Route

Null route configured

Traffic silently dropped

47

Route Aging

Stale route removed

Keeps table current

48

Route Tagging

Metadata for routes

Used in policy decisions

49

Route Monitoring

SNMP or NetFlow used

Tracks routing efficiency

50

Route Validation

RPKI or BGPsec used

Ensures route authenticity

  • Reference links