Comments on: ARP Probe and ARP Announcement

By: Lucinda Byrd

Lucinda Byrd — Sat, 08 Aug 2026 14:47:58 +0000

The distinction between a gratuitous ARP and an ARP probe is important when interpreting duplicate IP address detection in Cisco Packet Tracer, especially because the simulation may represent the packets differently from real network behavior. A clearer explanation of the packet fields and the purpose of each ARP message would make the example easier to follow. Discussions and experiences shared through Sandboxx reviews can also be useful when comparing how different technical tools present network scenarios and troubleshooting information.

By: Rishita

Rishita — Thu, 17 Apr 2025 08:41:57 +0000

I have a question if anyone can help with it..

Why an arp announcement is a request arp? What response is it seeking?

By: hamzayn

hamzayn — Thu, 29 Dec 2022 09:14:19 +0000

This is a very nice article. Although I have a concern. Do the hosts still learn the mapping with 0.0.0.0 sender IP in the ARP probe? Obviously, this wouldn’t have any effect if it does because technically a packet will never originate from 0.0.0.0 and the cache won’t get polluted…. I just want to clarify if it adds this to the ARP cache table.

By: Ali Rustem

Ali Rustem — Wed, 14 Dec 2022 07:54:43 +0000

I am a certified network architect, and I can say this is the best networking article I have ever read. Not just for ARP, in general I am speaking. It is very well-organized, well-explained with practical examples (pcaps) and animations. 8 years in networking business and I feel that I really, finally, understand ARP and all its flavors. Man you are the best!!!!

By: Ed Harmoush

Ed Harmoush — Tue, 26 Apr 2022 20:41:38 +0000

In reply to Bharath.

Without seeing a packet capture, you can’t know whether it was an ARP Probe or Gratuitous ARP. But the article above shows how to tell an ARP Probe vs Gratuitious arp, so this should be something you can test yourself.

Also, the video is using packet tracer, which is a network simulator — it doesn’t always work exactly the way real life does.

By: Ed Harmoush

Ed Harmoush — Tue, 26 Apr 2022 20:38:48 +0000

In reply to Rafael. DHCP server keeps track of what is assigned. It doesn't actively check if something is/isn't in use, it relies on its own logs of what it has already given out and what it hasn't.

By: Bharath

Bharath — Sun, 17 Apr 2022 18:24:25 +0000

https://www.youtube.com/watch?v=g4WJ4I6XmXE&list=PLruzrX735K0iSB4Xhirpah6K49GxiTSUi&index=4

I came across this video where Cisco packet tracker was used to demonstrate the duplicate IP address issue. In this example the packet tracker software shows that the ARP packet sent is gratuitous ARP and not the probe. Can you provide clarity on this? would really appreciate it.

Thanks
B

By: Rafael

Rafael — Sat, 09 Apr 2022 06:02:09 +0000

Like the ARP Probe, does the DHCP Server also check if an IP address is already being used by another Host before offering it? For example: The DHCP Server makes a “Ping ECHO REQUEST” on the IP address before starting the DHCP Offer and after the DHCP Server sends a “DHCP ACK” the client also starts a check if the IP Address is not already being used by another device through the ARP Probe. Is there this junction of the DHCP Server testing the IP before offering it with a “Ping” and after assigning the IP Address to the client with the confirmation “DHCP ACK” the client also does a verification with the ARP Probe?

By: Ed Harmoush

Ed Harmoush — Sat, 13 Mar 2021 21:28:52 +0000

In reply to Robert Vogler. You'd have to send me a packet capture of the IPDT probes and we could compare them to the G.ARP / ARP Probe packet captures in the article series. PS: Is this the same Robert Vogler I worked with back at Rackspace =) ?

By: Robert Vogler

Robert Vogler — Wed, 03 Mar 2021 21:39:09 +0000

Can you clarify how the ARP probe differs from the IPDT (IP Device Tracking) Probe? IPDT sometimes causes duplicate IP 0.0.0.0 errors.