CDP Behavior When an Interface Has No IP Address
Configure and verify Layer 2 discovery protocols (Cisco Discovery Protocol and LLDP)
Answer
Correct answer: B — CDP still runs normally and reports the IP address of another interface on the adjacent device when its CDP interface has no address.
In a CDP environment, what happens when the CDP interface on an adjacent device is configured without an IP address?
Community Insight
The question tests whether CDP requires an IP address on the discovery interface itself, and the trap is trusting Packet Tracer output over Cisco's documented substitution behavior.
This page examines Cisco Discovery Protocol operation when the CDP-enabled interface of an adjacent device has no IP address configured. Cisco's own CDP configuration documentation states the device substitutes another interface's IP address, which makes option B the defensible answer despite lab simulations showing an empty field.
Option C is the most common wrong pick, because testers in Packet Tracer and physical labs see an empty IP field in 'show cdp neighbors detail' and assume CDP simply omits address information rather than borrowing another interface's address.
Community Discussion (96 comments)
sowmi123
👍 1
Selected: B
If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. refer-https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
Tompoo
👍 1
Selected: B
CDP (Cisco Discovery Protocol) operates at Layer 2, so the interface itself does not need an IP address for CDP to function. If the CDP-enabled interface has no IP address, the device can advertise an IP address from another interface as its management/address information.
JRossJ
👍 1
Selected: B
“If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.” https://www.cisco.com/c/en/us/td/docs/routers/ios/config/17-x/syst-mgmt/b-system-management/m_nm-cdp-discover-xe.html
alexwow
👍 1
Selected: C
I tried in production enviorament and the correct answer is C.
Pierre_Mon_Frere
👍 1
Selected: B
Answer is B according to Cisco: Restrictions for Using Cisco Discovery Protocol: "If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface." Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
GOLDJUNGE
👍 1
Selected: B
I've tested it on EVE-NG and it really is B. At first I thought it will be C, because it take a few moments until cdp show this IP address of another interface. But if you test it and wait for about 1 min, the output will be updated and there will be an IP-Adress of another interface. So B is correct.
ITFreak
👍 2
Selected: C
CDP (Cisco Discovery Protocol) is a Layer 2 protocol, so it does not require IP addressing to function.
546716d
👍 1
Selected: C
C. CDP operates normally, but it cannot provide IP address information for that neighbor
OPEN_HI_MUR
👍 1
Selected: C
To be honest, this question is tricky. It doesn't state that any other interface has an IP address, also, in a real world environment, CDP will look at the management IP interface. I still think C is the most correct answer tho.
Scovin720
👍 2
Selected: C
100% the answer is C. Test it for yourself. It may work differently elsewhere in other programs, but the CCNA test is built around packet tracer so B must be the answer.
fb8c9bb
👍 1
Selected: C
Cisco Discovery Protocol (CDP) operates at Layer 2, so it does not require IP addresses to function.
bual12345678
👍 1
Selected: B
CDP (Cisco Discovery Protocol) operates normally without an IP address on the interface, but it cannot provide IP address information for that neighbor. It still shares other details like device ID and platform.
orxan1492
👍 1
Selected: C
CDP работает нормально
enzo3700
👍 2
Selected: C
Must be C "CDP operates normally, but it cannot provide IP address information for that neighbor". CPD works fine even without IP addresses
aburukelvin
👍 2
Selected: C
I would go with C because CDP does not provide information of another device connected to the neighbor only the information of the immediate neighbor and its direct cdp enabled interface.
69b32af
👍 2
Selected: C
CDP operates through L2 communication, so it will be normally working, but can't get IP address information. So... the answer is C
TT2215
👍 1
Selected: C
In a CDP (Cisco Discovery Protocol) environment, when the CDP interface on an adjacent device is configured without an IP address, CDP operates normally, but it cannot provide IP address information for that neighbor.
riteshm42
👍 1
Selected: C
CDP gathers and exchanges information about directly connected Cisco devices, such as the device ID, port ID, capabilities, platform, and IP address if it is configured. If an interface does not have an IP address, CDP will still function normally but will not be able to provide IP address information for that particular neighbor interface. Given this understanding, Option C remains the correct answer: CDP operates normally, but it cannot provide IP address information for that neighbor. It's possible that the source suggesting Option B is mixing up concepts. For example, another interface on the same device might have an IP address, but CDP would not use it to fill in the missing information for an interface that does not have an IP address.
SliCkR
👍 1
Selected: C
Explanation: CDP is a Layer 2 protocol, so it does not require an IP address to function. If the adjacent device's interface does not have an IP address configured, CDP will still operate and provide information such as device ID, port ID, capabilities, and platform. However, since there is no IP address configured on the interface, CDP will not be able to provide IP address information for that specific neighbor. The other options are incorrect because: A: CDP does not become inoperable; it continues to function at Layer 2. B: CDP does not use the IP address of another interface; it simply cannot provide IP address information for the interface without an IP. D: CDP can still provide other information (e.g., device ID, port ID) even if the IP address is missing. :::Deepseek
riteshm42
👍 1
Selected: C
Guys, CDP is layer 2 protocol it does not need IP address to get the neighbour details. The correct option is C. You can also research on web or through Different AI.
Xdarkrai
👍 1
Selected: C
The information given by CDP will just be missing an Ip-address
jojolabubu
👍 1
Selected: B
ChatGPT voted C Me: "Won't it show the IP address of another interface of the device?" ChatGPT: "Yes, you're correct! If a device has multiple interfaces and one of those interfaces has an IP address configured, CDP will display the IP address of a different interface if it’s available."
khamva
👍 1
Selected: C
CDP works on layer 2. It means there is no require for an IP address of the neighbor device to collect its information. The neigbors devices are directly connected, they can learn each other's MAC address.
SupernovaBoom
👍 1
Selected: C
CDP is a Layer 2 protocol, which means it operates independently of Layer 3 (IP) addresses. As a result, CDP can still exchange information such as device identifiers, port identifiers, capabilities, and platform information with neighboring devices, even if the interface does not have an IP address configured. However, without an IP address on the interface, CDP cannot provide IP address information for that neighbor because there is no IP address to report. Despite this, other information can still be exchanged and displayed through CDP.
Simrankoor
👍 2
i think its c,
Joshua25
👍 3
Selected: C
Definitely C. Verified on real Cisco hardware - a L3 switch and a router. SW1 port #5: 10.0.0.1 R1 port #1: no ip addr port #3: 172.16.1.1 SW1#5 connected to R1 #1 SW1# show cdp neighbors detail Information about R1 is displayed, without any IP address Particularly, 172.16.1.1 is not displayed at all. R1#show cdp neighbors detail It displays SW1 information with IP address 10.0.0.1
Joshua25
👍 1
Swapped the Switch and the Router, and tested again. Result is the same. Still C is correct. SW1 port #5 10.0.0.1 port #6 no ip R1 port #1 172.16.1.1 SW1 #6 connected to R1 #1 Still, the command [show cdp neighbors detail] from R1 does NOT show SW1's IP address. The Cisco article quoted by some people is either incorrect or talking about some situation
Mr0Robot
👍 1
it should be C , CDP, and LLDP both are layer 2 protocols
MicroDiff
👍 2
Selected: C
100% is C
cybercerberes
👍 1
Selected: B
C. CDP uses the IP address of another interface for that neighbor. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.
tumajay
👍 4
Selected: C
It is not B. Why majority picked B is beyond my networking comprehension. Cdp is a layer 2 protocol but can get ip info of an interface IF it has. Not picking the IP of another interface. Why would it even do that? To achieve what? This one i avoid the majority vote
tumajay
👍 1
Since there is no way to delete my previous comment, I withdraw my comment. This is directly from cisco site. “Restrictions” for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.* So it’s a restriction of cdp. Correct answer is B
KT_Yu
👍 1
If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html#GUID-3C4F2637-ED36-4EC0-9CD5-B73C0CF9DBEC
Sarooor
👍 2
Selected: C
C is the correct answer
593554d
👍 1
Restrictions for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
4ffc2ad
👍 1
If cdp used ip, it wouldn't work on l2 switch
JulesAZ
👍 2
Selected: B
Thought it was C Researched and Read the question ....... its B...... CDP is a Layer 2, media-independent, and network-independent protocol that runs on Cisco devices and enables networking applications to learn about directly connected devices nearby2. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface
JulesAZ
👍 2
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html in the 'Restrictions' paragraph.
picho707
👍 2
Selected: B
Confirmed in my LAB. B is the answer.
1stAid
👍 3
Selected: C
C. It will only show info of the interface it's connected to, not another interface info like answer B. Other interface might be connected to something else.
Predator_hb
👍 2
Selected: B
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
MaxaMillion
👍 3
Answer is C. CDP Works on Layer 2 the Data Link layer and does not care if there is an IP configured or not. It will only list the IP address with show cdp neighbors detail command or show cdp interfaces or show cdp interface f0/0. The IP address field will be blank if no IP is assigned.
berpiy1028
👍 1
The answer is C. The question didn't mention that other interfaces have IP addresses, so we should assume that other ports are also not configured with IP addresses, unless IP addresses are automatically generated by default.
Sant11
👍 2
Selected: B
Restrictions for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html#GUID-3C4F2637-ED36-4EC0-9CD5-B73C0CF9DBEC
Yinxs
👍 2
Selected: B
I tested it in GNS3. B is right. C is correct only if no ip address in any interfaces of this neighbor or the neighbor is a switching with no ipaddress.
tubirubs
👍 1
It's show when do not have IP aderess in the direct interface conected Router#show cdp neighbors detail Device ID: Router Entry address(es): Platform: cisco ISR4300, Capabilities: Router Interface: GigabitEthernet0/0/0, Port ID (outgoing port): GigabitEthernet0/0/0 Holdtime: 143 Version : Cisco IOS Software [Everest], ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 16.6.4,RELEASE SOFTWARE (fc3) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2018 by Cisco Systems, Inc. Compiled Sun 08-Jul-18 04:33 by mcpre advertisement version: 2 Duplex: full
tubirubs
👍 1
And this, when have IP configured Router#show cdp neighbors detail Device ID: Router Entry address(es): IP address : 10.0.0.1 Platform: cisco ISR4300, Capabilities: Router Interface: GigabitEthernet0/0/0, Port ID (outgoing port): GigabitEthernet0/0/1 Holdtime: 166 Version : Cisco IOS Software [Everest], ISR Software (X86_64_LINUX_IOSD-UNIVERSALK9-M), Version 16.6.4,RELEASE SOFTWARE (fc3) Technical Support: http://www.cisco.com/techsupport Copyright (c) 1986-2018 by Cisco Systems, Inc. Compiled Sun 08-Jul-18 04:33 by mcpre advertisement version: 2 Duplex: full
Lovesly
👍 2
B is correct. I just tried it in GNS3, and the "show cdp neighbors detail" command response included the ip address of another interface of the router.
_mva
👍 1
B is the correct answer. Using GNS3 and assigning an IP address to any interface not connecting to a neighboring switch results in that IP address showing under Management IP in the neighbor details sh command.
dropspablo
👍 2
unfortunately this is what happens, according to the cisco documentation (and GNS3 according to 4aynick), so we have to pay attention to the repeated IP addresses in the CDP "show" outputs.
AllyK
👍 2
I came across this issue real life. I was having an issue with being unable to ssh into a switch. I used 'cdp neighbor detail' on a switch I knew was a neighbor. The output was the same as all the others, except there was no IP address. The correct answer is C.
dropspablo
👍 2
Thank you, yes correct answer is B.
funkymonksarmy
👍 2
I cheked it and it shows ip address of another interface B is correct
Jorro99404
👍 2
Selected: B
"If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface."
Brocolee
👍 7
Dude, I got confused with you here. You said Packet Tracer isn't reliable and therefore you disagree with his reasoning..... But then you agree with his answer. Lol wtf?
Dunedrifter
👍 2
If B is true, cdp won't be a reliable network mapping utility. You wouldn't be able to map directly connected devices correctly if B is true.
dropspablo
👍 2
Selected: C
answer C is correct
👍 2
Answer B is correct. It's in Cisco's documentation.
Kyoxi
👍 2
Selected: C
c is correct
dearc
👍 2
Selected: C
https://learningnetwork.cisco.com/s/question/0D53i00000Kt3MpCAJ/how-does-cdp-work-without-l3-addresses
elixirwell
👍 3
Selected: B
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.htm
linuxlife
👍 2
Restrictions for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
daddydagoth
👍 4
Selected: B
Bruh, Cisco's own documentation says it's B then it's bloody B! Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
Dutch012
👍 2
Selected: C
the answer would be B, in the assumption that the adjacent device has another interface with an IP address, but the thing is the question didn't mention another IP interface for the adjacent device, so it's safer to choose C.
4aynick
👍 4
Selected: B
I was check it in gns3. Correct B
khird
👍 1
I think C is the answer, as the question says "The device is not configured" meaning any interface on that device has no IP
jibon_22
👍 1
100% correct: do it on packet tracer, then you will understand > C
rivera82
👍 3
Selected: C
Although CDP is a Layer 2 protocol but we can check the neighbor IP address with the “show cdp neighbor detail” command. If the neighbor does not has an IP address then CDP still operates without any problem. But the IP address of that neighbor is not provided.
Djent
👍 1
Selected: C
Why does CDP need another interface's IP address? CDP neighbor relationship will still be formed even if the other switch has no IP addresses at all. So C should be right. Besides, no information about the other switch having IP addresses is mentioned in the question, in which case it would be B.
Djent
👍 1
Let's say that one of the switches is a distribution layer switch with no IP addresses. Only trunks and etherchannels are configured for network availability and no management IP as well. As long as CDP is running on both these connected switches, they will form as CDP neighbors regardless of an IP. Please correct me if I've got anything wrong here
miki1001
👍 1
Selected: B
Restrictions for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.
MDK94
👍 5
This is a terrible question. In Cisco documentation it states that "If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface." But when you actually test this in packet tracer or on physical lab equipment (I tested on both) NO IP address will be shown for the other routers interfaces, not loopback not physical interface, nothing. Meaning that we cannot be sure what the actual answer is. I think the best hope is to go with the documentation and hope that it's the correct answer when in reality it isn't.
daddydagoth
👍 3
This is absoultely awful but true. This exam is a mess
Marcos9410
👍 3
Selected: B
B is correct
i_am_confused
👍 2
Selected: C
I just tried this in packet tracer with 2911 routers. When no ip address was configured, the neighbor router just showed a blank when issued the "show cdp neighbors detail" command. However, if an ip address is previously configured, and then a no ip address configured after to remove the ip address, the old ip address stayed when the neighbor used "show cdp neighbors detail". Yes I fast forwarded to make sure timers weren't the issue. At no point did the neighbor advertise another interface's ip address. I think the answer is C.
ZUMY
👍 2
Going with B Restrictions for Using Cisco Discovery Protocol Cisco Discovery Protocol functions only on Cisco devices. Cisco Discovery Protocol is not supported on Frame Relay multipoint subinterfaces. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.
ScorpionNet
👍 1
C is correct because CDP is a Layer 2 Function NOT Layer 3. It can still identify device IDs without IP Addresses. So C is the correct answer. It also the same answer comes to an Open Standard Protocol LLDP.
Shamwedge
👍 1
Gere's Cisco reference says it should be B
onikafei
👍 2
Selected: B
Answer is b
awashenko
👍 2
Honestly B and C are both correct. I'm not sure what one is more correct. Some of Ciscos questions are dumb. This is set up for people who know about CDP to get stumped and still get the questions wrong.
Mahmood4IPEng
👍 3
The question says that the CDP "uses" the ip address of another interface and this is incorrect as CDP doesn't need IP address to work so option C is the correct answer
Carter_Milk
👍 1
I am going for C. It can provide another IP address but not an IP for that particular neighbour?
ZUMY
👍 4
B is correct! If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP addres
ddban
👍 73
I tested in Packet tracer and I don't see that CDP uses an IP address of another interface for the CDP neighbor, it just leaves it empty but still works as usual. I don't see how you guys say it is B, but the simulation on PT says otherwise. I'm going with C.
dropspablo
👍 5
According to 4aynick who tested it through GNS3 and the CISCO documentation, answer B is correct, perhaps in Packet Tracer there is indeed this limitation, but it should include the ip address of another interface in an example of a #show cdp neighbors detail command, which does not happen leaving the ip address field empty (as I tested), but in GNS3 it manages to acquire the ip address of another interface (as mentioned by 4aynick), as well as also mentions the CISCO documentation, in this case, taking this into account limitation of Packet Tracer, I agree with answer B “updates the ip address of another interface”. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html#:~:text=Restrictions%20for%20Using%20Cisco%20Discovery%20Protocol,-Cisco%20Discovery%20Protocol&text=Cisco%20Discovery%20Protocol%20is%20not,the%20non%2DIP%20address%20interface
Bhrino
👍 4
Packet tracer isn’t really reliable for something so in theory I believe it should be c
Nicocisco
👍 5
yeah tested in lab to, and the switch don't see other interface of my router
Nicocisco
👍 10
When tested in the lab, the behaviour described in the link does not occur
youtri
👍 3
the correct is B Restrictions for Using Cisco Discovery Protocol • If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface.
oooMooo
👍 6
Read his link! "If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface." B is correct, as stated by Gere.
Gere
👍 35
The Right answer is B. If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface. Reference: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
Aval0n1
👍 9
What is the another interface? The C is correct. CDP does not need IPs to works normally https://learningnetwork.cisco.com/s/question/0D53i00000Kt3Mp/how-does-cdp-work-without-l3-addresses
admin1982
👍 2
Correct answer is C. CDP is a Layer 2 protocol, so there is no need for IP connectivity.
mali95
👍 2
Correct because CDP runs at the Physical layer, so even without IP configured it'd still provide neighbor's informations
Cristy
👍 3
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/cdp/configuration/15-mt/cdp-15-mt-book/nm-cdp-discover.html
Cristy
👍 9
I think the right answers should be B
Comments & Corrections
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Expert Analysis
Why the Answer Is Correct
Cisco's CDP configuration guide states explicitly: "If a neighbor has no IP address on an interface enabled with Cisco Discovery Protocol, the IP address of another interface will be updated as IP address for the non-IP address interface." CDP is a Layer 2 multicast protocol that does not need an IP address to run, so the neighbor relationship stays fully functional while the address field is populated from a different interface on that device. This directly matches option B: normal CDP operation plus a substituted IP address for the neighbor. Gere and oooMooo both cite this exact documented sentence, and it is vendor-official doctrine for exam purposes.Why the Other Options Are Wrong
Option A is wrong because CDP never depends on an IP address to function; it sends periodic multicast frames on the wire regardless of addressing. Option C describes what several testers observed in Packet Tracer, but it contradicts the published Cisco behavior and only reflects a simulator limitation rather than the documented protocol result. Option D is clearly false, since CDP still exchanges the device ID, port ID, platform, capabilities, and other TLVs even when no address is present on that interface. The distinction between C and B hinges on whether the address field is merely left blank or back-filled from another interface on the same device.Community Comment Notes
Gere quoted the Cisco guide verbatim: "the IP address of another interface will be updated as IP address for the non-IP address interface," and oooMooo repeated that same citation to defend B. On the other side, ddban reported "I don't see how you guys say it is B" after testing in Packet Tracer, and MDK94 noted that in "packet tracer or on physical lab equipment" no IP address appears. Nicocisco confirmed the same after lab testing, saying "the switch don't see other interface of my router," while dropspablo countered that GNS3 testing does show the other interface address, suggesting a platform difference rather than a protocol change.Official Reference
Exam Strategy
When a vendor documentation quote is attached to a question, treat the published behavior as the exam-correct answer even if a simulator prints something different. Recognize that CDP is Layer 2 and always operates without IP addressing, so eliminate options claiming the protocol stops working.
Frequently Asked Questions
Why is C wrong if Packet Tracer shows an empty IP address field?
Packet Tracer simplifies CDP output, but Cisco's configuration guide says another interface's IP is substituted. The exam expects the documented behavior, not the simulator's display.
Does CDP stop working if the interface has no IP address?
No. CDP is a Layer 2 protocol that exchanges multicast frames without any IP addressing, so neighbor discovery continues normally regardless of interface IPs.
Related Analysis
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