APIPA - Automatic Private IP Addressing
What is APIPA?
APIPA stands for Automatic Private IP Addressing. It’s a feature in Windows and some other operating systems that automatically assigns an IP address to a device when a DHCP server is unavailable.
Why is APIPA Useful?
Allows basic network communication even when the DHCP server is down.
Provides a fallback mechanism for IP addressing.
Useful in peer-to-peer and troubleshooting environments.
Ensures devices can still talk locally when central IP management fails.
How it works?
Device tries DHCP – When a device joins a network, it first tries to get an IP address from a DHCP server.
No DHCP response – If no DHCP server responds, the device assigns itself an IP address from a reserved range.
APIPA address assigned – The device picks an IP from 169.254.0.1 to 169.254.255.254.
Local communication only – The device can communicate with other devices using APIPA addresses on the same subnet.
Where is APIPA used?
Small peer-to-peer networks – Where there’s no DHCP server.
Temporary fallback – When DHCP fails, APIPA allows basic LAN communication.
Troubleshooting – Seeing an APIPA address helps identify DHCP-related issues.
Which OSI Layer does this protocol belong to?
Network Layer (Layer 3)
APIPA operates at the Network Layer because it involves IP address assignment and basic IP-based communication.
It does not interact with user applications directly.
It’s part of the operating system’s IP configuration system, not application logic.
Topics in this section,
In this section, you are going to learn
Terminology
Version Info
sno |
APIPA Version |
RFC / Standard |
Core / Contribution |
Year |
|---|---|---|---|---|
1 |
IPv4 Link-Local Addressing |
RFC 3927 |
Core |
2005 |
Setup
Setup
DHCP Discover Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
1 |
DHCP Discover |
Sent by a host to discover DHCP servers; APIPA is used if no server responds |
~300 600 |
op |
Message type (1 = request) |
1 |
|
htype |
Hardware type (1 = Ethernet) |
1 |
|
hlen |
Hardware address length (6 for MAC) |
1 |
|
hops |
Used by relay agents |
1 |
|
xid |
Transaction ID |
4 |
|
secs |
Seconds elapsed since client started trying to boot |
2 |
|
flags |
Flags (e.g., broadcast bit) |
2 |
|
ciaddr |
Client IP address (0.0.0.0 if unknown) |
4 |
|
yiaddr |
Your’ IP address (offered by server) |
4 |
|
siaddr |
Server IP address |
4 |
|
giaddr |
Gateway IP address |
4 |
|
chaddr |
Client hardware address (MAC) |
16 |
|
sname |
Optional server host name |
64 |
|
file |
Boot file name |
128 |
|
options |
DHCP options (e.g., message type, requested IP) |
~60 312 |
ARP Request Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
2 |
ARP Request |
Used to check if the randomly chosen APIPA address is already in use |
~28 60 |
Hardware Type |
Ethernet = 1 |
2 |
|
Protocol Type |
IPv4 = 0x0800 |
2 |
|
Hardware Size |
MAC address length (6) |
1 |
|
Protocol Size |
IP address length (4) |
1 |
|
Opcode |
1 = request, 2 = reply |
2 |
|
Sender MAC |
MAC address of sender |
6 |
|
Sender IP |
IP address of sender |
4 |
|
Target MAC |
MAC address of target (0s in request) |
6 |
|
Target IP |
IP address being queried |
4 |
ARP Reply Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
3 |
ARP Reply |
Sent if another host already uses the IP address |
~28 60 |
Hardware Type |
Specifies the type of hardware (1 = Ethernet) |
2 |
|
Protocol Type |
Specifies the protocol (0x0800 = IPv4) |
2 |
|
Hardware Size |
Length of hardware address (MAC = 6 bytes) |
1 |
|
Protocol Size |
Length of protocol address (IPv4 = 4 bytes) |
1 |
|
Opcode |
Operation code (2 = ARP Reply) |
2 |
|
Sender MAC Address |
MAC address of the device sending the reply |
6 |
|
Sender IP Address |
IP address of the device sending the reply |
4 |
|
Target MAC Address |
MAC address of the device that sent the ARP request |
6 |
|
Target IP Address |
IP address that was queried in the ARP request |
4 |
ICMP Echo Request/Reply Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
4 |
ICMP Echo Request/Reply |
Used optionally to test connectivity after assigning an APIPA address |
~28 64 |
Type |
Indicates the message type: 8 for Echo Request, 0 for Echo Reply |
1 |
|
Code |
Provides further context for the type; always 0 for Echo messages |
1 |
|
Checksum |
Used to verify the integrity of the ICMP message |
2 |
|
Identifier |
Helps match requests and replies (often used to identify the process ID) |
2 |
|
Sequence Number |
Sequence number to track multiple requests |
2 |
|
Payload/Data |
Optional data sent with the request (e.g., timestamp or filler bytes) |
~20 56 |
Gratuitous ARP Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
5 |
Gratuitous ARP |
A special ARP request sent by a host to announce its IP address |
~28 60 |
Hardware Type |
Specifies the hardware type (1 = Ethernet) |
2 |
|
Protocol Type |
Specifies the protocol (0x0800 = IPv4) |
2 |
|
Hardware Size |
Length of the hardware address (MAC = 6 bytes) |
1 |
|
Protocol Size |
Length of the protocol address (IPv4 = 4 bytes) |
1 |
|
Opcode |
Operation code (1 = ARP Request, even though it’s unsolicited) |
2 |
|
Sender MAC Address |
MAC address of the host sending the ARP |
6 |
|
Sender IP Address |
IP address of the host sending the ARP (same as target IP in Gratuitous ARP) |
4 |
|
Target MAC Address |
Set to all zeros (00:00:00:00:00:00) in Gratuitous ARP |
6 |
|
Target IP Address |
Same as the sender IP address |
4 |
DHCP Offer / ACK Packet
S.No |
Protocol Packets |
Description |
Size(Bytes) |
|---|---|---|---|
6 |
DHCP Offer / ACK |
If a DHCP server becomes available later, these packets may override APIPA |
~300 600 |
op |
Message type: 2 for reply (Offer/ACK) |
1 |
|
htype |
Hardware type (1 = Ethernet) |
1 |
|
hlen |
Hardware address length (6 for MAC) |
1 |
|
hops |
Used by relay agents (usually 0) |
1 |
|
xid |
Transaction ID to match requests and replies |
4 |
|
secs |
Seconds elapsed since client started trying to boot |
2 |
|
flags |
Flags (e.g., broadcast bit) |
2 |
|
ciaddr |
Client IP address (filled in by client if known) |
4 |
|
yiaddr |
Your’ IP address (offered or assigned by server) |
4 |
|
siaddr |
Server IP address |
4 |
|
giaddr |
Gateway IP address (used by relay agents) |
4 |
|
chaddr |
Client hardware address (MAC) |
16 |
|
sname |
Optional server host name |
64 |
|
file |
Boot file name |
128 |
|
options |
DHCP options (e.g., message type, lease time, subnet mask, router, DNS) |
~60 300 |
APIPA Usecases
Sno |
Feature |
Description |
|---|---|---|
1 |
Automatic IP Assignment |
Assigns an IP address in the 169.254.0.0/16 range when no DHCP server is found. |
2 |
No Manual Configuration Needed |
Enables plug-and-play networking without user intervention. |
3 |
Uses ARP for Conflict Detection |
Checks for IP conflicts using ARP before assigning an address. |
4 |
Limited to Local Subnet |
Communication is restricted to devices on the same local network segment. |
5 |
Fallback Mechanism |
Acts as a backup when DHCP fails or is unavailable. |
6 |
Zero-Configuration Networking |
Supports basic networking without DNS, DHCP, or manual setup. |
7 |
IPv4 Only |
APIPA is defined only for IPv4 (RFC 3927); not used in IPv6. |
Automatic IP Assignment - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
DHCP Server Unavailable |
Disconnect DHCP server |
Device assigns IP in 169.254.x.x range |
2 |
DHCP Server Available |
Connect to DHCP server |
Device receives IP from DHCP |
3 |
APIPA Activation |
Disable DHCP manually |
APIPA assigns IP automatically |
4 |
APIPA IP Range Check |
Check assigned IP |
IP is in 169.254.0.1 to 169.254.255.254 |
5 |
Subnet Mask Check |
Verify subnet mask |
Subnet mask is 255.255.0.0 |
6 |
Gateway Absence |
Check default gateway |
No default gateway assigned |
7 |
DNS Absence |
Check DNS settings |
No DNS server assigned |
8 |
Local Communication |
Ping another APIPA device |
Ping successful within same subnet |
9 |
Internet Access Blocked |
Try accessing internet |
Access fails without gateway |
10 |
APIPA to DHCP Transition |
Reconnect DHCP server |
Device switches to DHCP IP |
11 |
DHCP to APIPA Transition |
Disconnect DHCP |
Device falls back to APIPA IP |
12 |
Static IP Override |
Assign static IP |
Static IP overrides APIPA |
13 |
Duplicate IP Detection |
Simulate IP conflict |
Device selects new APIPA IP |
14 |
IP Conflict Resolution |
Force duplicate IP |
Device reassigns new IP |
15 |
APIPA on Windows |
Enable APIPA on Windows |
IP assigned in 169.254.x.x range |
16 |
APIPA on Linux |
Enable APIPA on Linux |
IP assigned in 169.254.x.x range |
17 |
APIPA on macOS |
Enable APIPA on macOS |
IP assigned in 169.254.x.x range |
18 |
APIPA on IoT Device |
Disconnect DHCP |
Device assigns APIPA IP |
19 |
APIPA on Mobile Device |
Disable DHCP |
Mobile assigns APIPA IP |
20 |
APIPA on Virtual Machine |
Disable DHCP in VM |
VM assigns APIPA IP |
21 |
APIPA on Docker Container |
Disable DHCP |
Container assigns APIPA IP |
22 |
APIPA with Firewall Enabled |
Enable firewall |
APIPA still assigns IP |
23 |
APIPA with Antivirus |
Run antivirus |
No interference with APIPA |
24 |
APIPA with VPN |
Connect VPN |
VPN fails without internet |
25 |
APIPA with Proxy |
Set proxy manually |
Proxy unreachable without gateway |
26 |
APIPA with IPv6 Enabled |
Enable IPv6 |
IPv4 APIPA still functions |
27 |
APIPA with IPv6 Disabled |
Disable IPv6 |
APIPA IPv4 works normally |
28 |
APIPA with Network Isolation |
Isolate device |
Device assigns APIPA IP |
29 |
APIPA with Multiple NICs |
Use two NICs |
Only disconnected NIC uses APIPA |
30 |
APIPA with Bridged Network |
Use bridged adapter |
APIPA assigns IP if DHCP fails |
31 |
APIPA with NAT Network |
Use NAT adapter |
APIPA assigns IP if DHCP fails |
32 |
APIPA with Static Route |
Add static route |
Route ignored without gateway |
33 |
APIPA with Manual DNS |
Set DNS manually |
DNS resolves if reachable |
34 |
APIPA with Hostname Resolution |
Use hostname |
Fails without DNS |
35 |
APIPA with Bonjour |
Use Bonjour service |
Local discovery works |
36 |
APIPA with mDNS |
Use multicast DNS |
Local name resolution works |
37 |
APIPA with File Sharing |
Share files over APIPA |
File sharing works locally |
38 |
APIPA with Printer Sharing |
Share printer |
Printer accessible on same subnet |
39 |
APIPA with Remote Desktop |
Connect via RDP |
Works within APIPA subnet |
40 |
APIPA with Ping Test |
Ping APIPA IP |
Ping successful within subnet |
41 |
APIPA with Traceroute |
Run traceroute |
No route beyond local subnet |
42 |
APIPA with Network Reset |
Reset adapter |
APIPA IP reassigned |
43 |
APIPA with OS Update |
Update OS |
APIPA behavior remains unchanged |
44 |
APIPA with Sleep/Wake |
Sleep and wake device |
APIPA IP retained |
45 |
APIPA with Reboot |
Reboot device |
New APIPA IP assigned if DHCP unavailable |
46 |
APIPA with Network Diagnostics |
Run diagnostics |
Reports DHCP failure, APIPA fallback |
47 |
APIPA with Event Logs |
Check system logs |
Logs show DHCP failure and APIPA assignment |
48 |
APIPA with Network Profile |
Check network profile |
Marked as “Unidentified Network” |
49 |
APIPA with Security Software |
Run security scan |
No interference with APIPA |
50 |
APIPA with Network Monitoring Tool |
Use Wireshark |
Shows ARP and APIPA traffic |
No Manual Configuration Needed - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
No DHCP Server |
Disconnect DHCP server |
Device auto-assigns APIPA IP |
2 |
No Static IP Set |
No manual IP configured |
APIPA assigns IP automatically |
3 |
Plug-and-Play Network |
Connect device to network |
IP assigned without user input |
4 |
No Admin Rights |
User lacks admin access |
APIPA still assigns IP |
5 |
No Network Tools Installed |
No config tools available |
APIPA still functions |
6 |
No Network Profile |
No saved network profile |
APIPA assigns IP |
7 |
No Gateway Configured |
No gateway set |
APIPA assigns IP without gateway |
8 |
No DNS Configured |
No DNS set |
APIPA assigns IP without DNS |
9 |
No User Interaction |
No user input |
IP assigned automatically |
10 |
No Network Script |
No startup script |
APIPA still assigns IP |
11 |
No IP Conflict |
Unique APIPA IP assigned |
Device joins local network |
12 |
IP Conflict Detected |
Duplicate IP found |
New APIPA IP assigned |
13 |
No Reboot Required |
No restart needed |
IP assigned immediately |
14 |
No GUI Available |
No graphical interface |
APIPA assigns IP via system |
15 |
No CLI Commands Used |
No manual commands run |
IP assigned automatically |
16 |
No Configuration File |
No IP config file present |
APIPA assigns IP |
17 |
No DHCP Lease |
No lease obtained |
APIPA assigns fallback IP |
18 |
No Network Admin |
No admin intervention |
Device self-configures IP |
19 |
No Network Policy |
No group policy applied |
APIPA still works |
20 |
No Custom Scripts |
No automation scripts |
APIPA assigns IP |
21 |
No Registry Edits |
No registry changes |
APIPA functions normally |
22 |
No Driver Tweaks |
Default drivers used |
APIPA assigns IP |
23 |
No IP Reservation |
No DHCP reservation |
APIPA assigns IP |
24 |
No MAC Filtering |
No MAC rules applied |
APIPA assigns IP |
25 |
No VLAN Tagging |
No VLAN config |
APIPA assigns IP |
26 |
No Proxy Settings |
No proxy configured |
APIPA assigns IP |
27 |
No Firewall Rules |
No special rules |
APIPA assigns IP |
28 |
No Port Forwarding |
No port rules |
APIPA assigns IP |
29 |
No NAT Configuration |
No NAT setup |
APIPA assigns IP |
30 |
No Routing Table |
No static routes |
APIPA assigns IP |
31 |
No Hostname Set |
No hostname configured |
APIPA assigns IP |
32 |
No Domain Membership |
Not joined to domain |
APIPA assigns IP |
33 |
No Network Profile |
No saved profile |
APIPA assigns IP |
34 |
No Network Adapter Settings |
Default adapter settings |
APIPA assigns IP |
35 |
No IP Stack Customization |
Default TCP/IP stack |
APIPA assigns IP |
36 |
No IPv6 Enabled |
IPv6 disabled |
IPv4 APIPA still works |
37 |
No Internet Access |
No WAN access |
APIPA assigns IP for local use |
38 |
No DHCP Relay |
No relay agent |
APIPA assigns IP |
39 |
No BootP Support |
BootP not used |
APIPA assigns IP |
40 |
No PXE Boot |
PXE not used |
APIPA assigns IP |
41 |
No Network Diagnostics |
No tools run |
APIPA assigns IP |
42 |
No IP Renewal |
No manual renewal |
APIPA IP persists |
43 |
No IP Release |
No IP released |
APIPA IP remains |
44 |
No IP Flush |
No flush command used |
APIPA IP remains |
45 |
No Network Reset |
No reset performed |
APIPA assigns IP |
46 |
No Interface Restart |
Interface not restarted |
APIPA assigns IP |
47 |
No OS Reboot |
System not rebooted |
APIPA assigns IP |
48 |
No User Login |
IP assigned before login |
APIPA works at boot |
49 |
No Network Profile Switch |
Profile not changed |
APIPA IP remains |
50 |
No Configuration Wizard |
No setup wizard used |
APIPA assigns IP automatically |
Uses ARP for Conflict Detection - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
ARP Probe on IP Assignment |
Assign APIPA IP |
ARP probe sent to check for conflict |
2 |
ARP Response Received |
Another device responds |
IP conflict detected, new IP assigned |
3 |
No ARP Response |
No device responds |
IP assigned successfully |
4 |
Duplicate IP Detected |
Same IP already in use |
APIPA selects a different IP |
5 |
ARP Retry on Conflict |
Conflict detected |
APIPA retries with new IP |
6 |
ARP Timeout Handling |
No response within timeout |
IP assumed to be free |
7 |
ARP Broadcast Format |
Check ARP packet format |
Packet conforms to RFC 5227 |
8 |
ARP Probe Count |
Count ARP probes sent |
3 probes sent before assignment |
9 |
ARP Interval Timing |
Measure interval between probes |
Interval is 1 second (default) |
10 |
ARP Conflict Logging |
Log IP conflict event |
Conflict logged in system logs |
11 |
ARP Conflict Notification |
Notify user on conflict |
Notification shown (if supported) |
12 |
ARP Conflict Resolution |
Conflict detected |
New IP selected automatically |
13 |
ARP Conflict with Static IP |
Static IP responds to probe |
APIPA avoids that IP |
14 |
ARP Conflict with DHCP IP |
DHCP-assigned IP responds |
APIPA avoids that IP |
15 |
ARP Conflict with Another APIPA |
Another APIPA device responds |
IP conflict resolved |
16 |
ARP Conflict on Reboot |
Reboot device |
ARP probe sent again |
17 |
ARP Conflict on Wake |
Wake from sleep |
ARP probe sent again |
18 |
ARP Conflict on Network Change |
Change network |
ARP probe sent again |
19 |
ARP Conflict on Interface Reset |
Reset NIC |
ARP probe sent again |
20 |
ARP Conflict on Cable Reconnect |
Reconnect Ethernet |
ARP probe sent again |
21 |
ARP Conflict on Wi-Fi Reconnect |
Reconnect Wi-Fi |
ARP probe sent again |
22 |
ARP Conflict with Virtual Machine |
VM responds to probe |
IP conflict detected |
23 |
ARP Conflict with IoT Device |
IoT device responds |
IP conflict detected |
24 |
ARP Conflict with Printer |
Printer responds to probe |
IP conflict detected |
25 |
ARP Conflict with Router |
Router responds to probe |
IP conflict detected |
26 |
ARP Conflict with Mobile Device |
Phone responds to probe |
IP conflict detected |
27 |
ARP Conflict with NAS |
NAS responds to probe |
IP conflict detected |
28 |
ARP Conflict with Smart TV |
Smart TV responds |
IP conflict detected |
29 |
ARP Conflict with Game Console |
Console responds |
IP conflict detected |
30 |
ARP Conflict with APIPA Range |
Conflict within 169.254.x.x |
New IP selected |
31 |
ARP Conflict with Reserved IP |
Reserved IP responds |
IP not used |
32 |
ARP Conflict with Loopback |
Loopback responds (simulated) |
IP not used |
33 |
ARP Conflict with Broadcast |
Broadcast address used |
IP rejected |
34 |
ARP Conflict with Multicast |
Multicast address used |
IP rejected |
35 |
ARP Conflict with Gateway |
Gateway responds |
IP not used |
36 |
ARP Conflict with DNS Server |
DNS responds |
IP not used |
37 |
ARP Conflict with Proxy |
Proxy responds |
IP not used |
38 |
ARP Conflict with Firewall |
Firewall responds |
IP not used |
39 |
ARP Conflict with Duplicate MAC |
Same MAC responds |
IP conflict detected |
40 |
ARP Conflict with Spoofed IP |
Spoofed ARP reply |
IP conflict detected |
41 |
ARP Conflict with Delayed Response |
Late ARP reply |
IP reassigned |
42 |
ARP Conflict with No Response |
No reply received |
IP assigned successfully |
43 |
ARP Conflict with Multiple Replies |
Multiple replies received |
IP conflict detected |
44 |
ARP Conflict with Silent Device |
Device doesnt respond |
IP may be incorrectly assigned |
45 |
ARP Conflict with Busy Network |
High ARP traffic |
Conflict detection still works |
46 |
ARP Conflict with VLAN |
VLAN device responds |
IP conflict detected |
47 |
ARP Conflict with Bridged Network |
Bridged device responds |
IP conflict detected |
48 |
ARP Conflict with NAT |
NAT device responds |
IP conflict detected |
49 |
ARP Conflict with Wireless Bridge |
Bridge responds |
IP conflict detected |
50 |
ARP Conflict with Reused IP |
Previously used IP responds |
IP conflict detected and avoided |
Limited to Local Subnet - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
APIPA IP Assignment |
Assign APIPA IP |
IP is in 169.254.x.x range |
2 |
Subnet Mask Check |
Verify subnet mask |
Subnet mask is 255.255.0.0 |
3 |
No Default Gateway |
Check routing table |
No default gateway is set |
4 |
No Internet Access |
Try accessing external site |
Access fails |
5 |
Local Device Ping |
Ping another APIPA device |
Ping successful |
6 |
External Device Ping |
Ping internet IP |
Ping fails |
7 |
DNS Resolution |
Try resolving domain |
DNS fails without gateway |
8 |
Local File Sharing |
Share files between APIPA devices |
File sharing works |
9 |
Local Printer Access |
Access network printer with APIPA |
Printer accessible |
10 |
Remote Desktop Local |
RDP to another APIPA device |
Connection successful |
11 |
Remote Desktop External |
RDP to internet IP |
Connection fails |
12 |
Local HTTP Server |
Host HTTP server on APIPA |
Accessible from local subnet |
13 |
External HTTP Access |
Access external web server |
Fails without routing |
14 |
Local FTP Server |
Host FTP server on APIPA |
Accessible locally |
15 |
External FTP Access |
Access FTP on internet |
Fails without gateway |
16 |
Local Media Streaming |
Stream media between APIPA devices |
Streaming works |
17 |
Internet Streaming |
Try streaming from internet |
Fails |
18 |
Local Chat App |
Use LAN chat app |
Works between APIPA devices |
19 |
Online Chat App |
Use internet-based chat |
Fails without internet |
20 |
Local Game Server |
Host LAN game |
Discoverable on APIPA subnet |
21 |
Online Game Server |
Connect to online game |
Fails without internet |
22 |
Local Device Discovery |
Discover devices via mDNS |
Devices found locally |
23 |
Internet Device Discovery |
Discover cloud devices |
Fails |
24 |
Local Network Scan |
Scan APIPA subnet |
Devices detected |
25 |
External Network Scan |
Scan internet IPs |
No response |
26 |
Local File Transfer |
Transfer files via SMB |
Works on APIPA subnet |
27 |
Cloud File Transfer |
Upload to cloud |
Fails |
28 |
Local IP Camera Access |
Access camera on APIPA |
Stream works locally |
29 |
Cloud Camera Access |
Access cloud camera |
Fails |
30 |
Local NAS Access |
Access NAS on APIPA |
Accessible |
31 |
Cloud NAS Access |
Access cloud storage |
Fails |
32 |
Local IoT Device Control |
Control smart device on APIPA |
Works locally |
33 |
Cloud IoT Control |
Control via cloud |
Fails |
34 |
Local DHCP Server Ping |
Ping DHCP server |
Not reachable from APIPA |
35 |
Local Broadcast |
Send broadcast packet |
Received by local devices |
36 |
External Broadcast |
Send to external subnet |
Not delivered |
37 |
Local ARP Resolution |
Resolve local IP |
ARP works within subnet |
38 |
External ARP Resolution |
Resolve internet IP |
Fails |
39 |
Local Routing Table |
Check routes |
Only local subnet route exists |
40 |
Add Static Route |
Add route to external IP |
Still unreachable without gateway |
41 |
Local VPN Server |
Connect to VPN on APIPA |
Works locally |
42 |
External VPN Server |
Connect to VPN on internet |
Fails |
43 |
Local Proxy Server |
Use proxy on APIPA |
Works locally |
44 |
External Proxy Server |
Use internet proxy |
Fails |
45 |
Local DNS Server |
Use DNS on APIPA subnet |
Resolves local names |
46 |
External DNS Server |
Use public DNS |
Fails without gateway |
47 |
Local NTP Server |
Sync time with local NTP |
Works |
48 |
External NTP Server |
Sync time with internet NTP |
Fails |
49 |
Local Software Update |
Update from local repo |
Works if hosted locally |
50 |
Internet Software Update |
Update from internet |
Fails without internet access |
Fallback Mechanism - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
DHCP Server Down |
Disconnect DHCP server |
APIPA assigns fallback IP |
2 |
DHCP Timeout |
Simulate DHCP timeout |
APIPA assigns IP after timeout |
3 |
DHCP Lease Failure |
Fail to obtain lease |
APIPA assigns IP |
4 |
DHCP Server Unreachable |
Block DHCP server IP |
APIPA assigns IP |
5 |
DHCP Port Blocked |
Block port 67/68 |
APIPA assigns IP |
6 |
DHCP Server Crash |
Simulate server crash |
APIPA assigns IP |
7 |
DHCP Server Busy |
Simulate server overload |
APIPA assigns IP |
8 |
DHCP Server Misconfigured |
Use invalid DHCP config |
APIPA assigns IP |
9 |
DHCP Server Responds Late |
Delay DHCP response |
APIPA assigns IP after timeout |
10 |
DHCP Server Responds with Error |
Send DHCP NAK |
APIPA assigns IP |
11 |
DHCP Server Responds with Invalid IP |
Send out-of-range IP |
APIPA assigns fallback IP |
12 |
DHCP Server Responds with Duplicate IP |
IP already in use |
APIPA assigns new IP |
13 |
DHCP Server Responds with No Lease Time |
No lease duration |
APIPA assigns fallback IP |
14 |
DHCP Server Responds with No Subnet |
Missing subnet info |
APIPA assigns fallback IP |
15 |
DHCP Server Responds with No Gateway |
Missing gateway info |
APIPA assigns fallback IP |
16 |
DHCP Server Responds with No DNS |
Missing DNS info |
APIPA assigns fallback IP |
17 |
DHCP Server Responds with Corrupt Packet |
Malformed DHCP offer |
APIPA assigns fallback IP |
18 |
DHCP Server Responds with Wrong MAC |
MAC mismatch |
APIPA assigns fallback IP |
19 |
DHCP Server Responds with Wrong Hostname |
Hostname mismatch |
APIPA assigns fallback IP |
20 |
DHCP Server Responds with Wrong Options |
Invalid DHCP options |
APIPA assigns fallback IP |
21 |
DHCP Server Responds with Wrong IP Range |
IP outside subnet |
APIPA assigns fallback IP |
22 |
DHCP Server Responds with Expired Lease |
Lease already expired |
APIPA assigns fallback IP |
23 |
DHCP Server Responds with Reserved IP |
Reserved IP not assignable |
APIPA assigns fallback IP |
24 |
DHCP Server Responds with Static IP Conflict |
Conflict with static IP |
APIPA assigns fallback IP |
25 |
DHCP Server Responds with Loopback IP |
127.0.0.1 assigned |
APIPA assigns fallback IP |
26 |
DHCP Server Responds with Broadcast IP |
255.255.255.255 assigned |
APIPA assigns fallback IP |
27 |
DHCP Server Responds with Multicast IP |
224.0.0.1 assigned |
APIPA assigns fallback IP |
28 |
DHCP Server Responds with APIPA IP |
169.254.x.x assigned |
APIPA reassigns new IP |
29 |
DHCP Server Responds with Zero IP |
0.0.0.0 assigned |
APIPA assigns fallback IP |
30 |
DHCP Server Responds with Duplicate MAC |
MAC already in use |
APIPA assigns fallback IP |
31 |
DHCP Server Responds with No Response |
No DHCPACK received |
APIPA assigns fallback IP |
32 |
DHCP Server Responds with DHCPDECLINE |
Decline from client |
APIPA assigns fallback IP |
33 |
DHCP Server Responds with DHCPRELEASE |
Lease released |
APIPA assigns fallback IP |
34 |
DHCP Server Responds with DHCPINFORM |
No IP assigned |
APIPA assigns fallback IP |
35 |
DHCP Server Responds with DHCPDISCOVER Only |
No DHCPOFFER |
APIPA assigns fallback IP |
36 |
DHCP Server Responds with DHCPACK Timeout |
ACK not received |
APIPA assigns fallback IP |
37 |
DHCP Server Responds with DHCPNAK |
Negative acknowledgment |
APIPA assigns fallback IP |
38 |
DHCP Server Responds with DHCPACK to Wrong Client |
ACK to wrong MAC |
APIPA assigns fallback IP |
39 |
DHCP Server Responds with DHCPACK to Wrong IP |
ACK with wrong IP |
APIPA assigns fallback IP |
40 |
DHCP Server Responds with DHCPACK to Wrong Subnet |
ACK with wrong subnet |
APIPA assigns fallback IP |
41 |
DHCP Server Responds with DHCPACK to Wrong Lease Time |
Lease time = 0 |
APIPA assigns fallback IP |
42 |
DHCP Server Responds with DHCPACK to Wrong Gateway |
Invalid gateway |
APIPA assigns fallback IP |
43 |
DHCP Server Responds with DHCPACK to Wrong DNS |
Invalid DNS |
APIPA assigns fallback IP |
44 |
DHCP Server Responds with DHCPACK to Wrong Hostname |
Hostname mismatch |
APIPA assigns fallback IP |
45 |
DHCP Server Responds with DHCPACK to Wrong Options |
Invalid options |
APIPA assigns fallback IP |
46 |
DHCP Server Responds with DHCPACK to Wrong Broadcast |
Invalid broadcast |
APIPA assigns fallback IP |
47 |
DHCP Server Responds with DHCPACK to Wrong MTU |
Invalid MTU |
APIPA assigns fallback IP |
48 |
DHCP Server Responds with DHCPACK to Wrong Domain |
Invalid domain |
APIPA assigns fallback IP |
49 |
DHCP Server Responds with DHCPACK to Wrong Router |
Invalid router |
APIPA assigns fallback IP |
50 |
DHCP Server Responds with DHCPACK to Wrong Network |
Invalid network |
APIPA assigns fallback IP |
Zero-Configuration Networking - Testcases
S.No |
Test Case |
Description |
Expected Result |
|---|---|---|---|
1 |
No DHCP Server |
Disconnect DHCP |
Device assigns APIPA IP automatically |
2 |
No Manual IP Set |
No static IP configured |
Device self-assigns IP |
3 |
No DNS Configured |
No DNS server set |
Local communication still works |
4 |
No Gateway Configured |
No default gateway |
Local subnet communication works |
5 |
Plug-and-Play Setup |
Connect device to network |
Device joins network without setup |
6 |
Peer-to-Peer Communication |
Two APIPA devices communicate |
Communication successful |
7 |
File Sharing |
Share files between APIPA devices |
File transfer successful |
8 |
Printer Sharing |
Share printer over APIPA |
Printer accessible locally |
9 |
Media Streaming |
Stream media between APIPA devices |
Streaming works |
10 |
Remote Desktop |
Connect via RDP on APIPA |
Session established locally |
11 |
Device Discovery |
Discover devices via mDNS |
Devices visible on local subnet |
12 |
Bonjour Service |
Use Bonjour for service discovery |
Services found automatically |
13 |
mDNS Resolution |
Resolve local hostname |
Hostname resolves correctly |
14 |
No Admin Rights |
User lacks admin access |
APIPA still assigns IP |
15 |
No Configuration Tools |
No network tools installed |
APIPA still functions |
16 |
No Network Profile |
No saved profile |
Device joins local network |
17 |
No User Input |
No manual steps taken |
Device self-configures |
18 |
No Reboot Required |
No restart needed |
IP assigned immediately |
19 |
No Interface Restart |
Interface not restarted |
IP assigned automatically |
20 |
No Network Script |
No startup script |
APIPA assigns IP |
21 |
No Registry Edit |
No registry configuration |
APIPA works by default |
22 |
No CLI Commands |
No commands executed |
IP assigned automatically |
23 |
No GUI Access |
No graphical interface |
APIPA still works |
24 |
No Internet Access |
No WAN access |
Local subnet still functional |
25 |
No Router Present |
No router in network |
Devices still communicate locally |
26 |
No DHCP Relay |
No relay agent |
APIPA assigns IP |
27 |
No VLAN Config |
No VLAN tagging |
Devices communicate on same subnet |
28 |
No Proxy Config |
No proxy server |
Local communication unaffected |
29 |
No NAT Config |
No NAT setup |
Local subnet still works |
30 |
No Port Forwarding |
No port rules |
Local services still accessible |
31 |
No Static Routes |
No routing table entries |
Local subnet communication works |
32 |
No Hostname Set |
No hostname configured |
Device still discoverable via IP |
33 |
No Domain Join |
Not joined to domain |
Local communication still works |
34 |
No Network Policy |
No group policy applied |
APIPA functions normally |
35 |
No Firewall Rules |
Default firewall settings |
Local communication allowed |
36 |
No Antivirus Exception |
No AV rule set |
APIPA still assigns IP |
37 |
No Software Installation |
No third-party tools |
APIPA works with OS defaults |
38 |
No Configuration Wizard |
No setup wizard used |
Device joins network automatically |
39 |
No Network Diagnostics |
No diagnostics run |
APIPA assigns IP |
40 |
No IP Renewal |
No manual renewal |
IP remains valid |
41 |
No IP Release |
No release command used |
IP remains assigned |
42 |
No IP Flush |
No flush command used |
IP remains assigned |
43 |
No Network Reset |
No reset performed |
APIPA still functions |
44 |
No DHCP Lease |
No lease obtained |
APIPA assigns fallback IP |
45 |
No DHCP Offer |
No offer received |
APIPA assigns IP |
46 |
No DHCP ACK |
No acknowledgment received |
APIPA assigns IP |
47 |
No DHCP NAK |
No negative acknowledgment |
APIPA assigns IP |
48 |
No DHCPDISCOVER Sent |
DHCP disabled |
APIPA assigns IP |
49 |
No DHCP Server Response |
Server silent |
APIPA assigns IP |
50 |
No Configuration File |
No IP config file |
APIPA assigns IP automatically |
IPv4 Only - Testcases
Reference links