Comments on: Proxy ARP

By: Muhammad Abbas

Muhammad Abbas — Sat, 18 May 2024 11:16:01 +0000

i have read the Article ,but a bit confused as the address of host Y should be 10.3.4.55 as per diagram,but in the article it is mentioned ,that IP addrss of host Y is 72.3.4.55.
can any one clarify more.

By: train_wreck

train_wreck — Thu, 04 May 2023 06:32:53 +0000

Hello, nice article. There is another situation where proxy ARP is sometimes used. It is by wireless access points. Under normal conditions, ARP requests are broadcast to all clients. A WiFi access point sends the broadcasts to all associated WiFi clients. This can potentially eat up a lot of “airtime” and reduce performance of the WiFi network. To avoid this, some WAPs enable proxy ARP on the ethernet interface. Since the WAP will always know all of the MAC addresses of the WiFi clients connected to it, it can intercept incoming ARP requests from the ethernet side for clients associated to it, and respond with proper response for the WiFi client. Not all WAPs support this, and those that do may need it to be enabled manually in the configuration. Just FYI. Thanks.

By: lee

lee — Mon, 26 Dec 2022 16:33:11 +0000

thanks, bro, nice sharing, BTW, for some routers (such as Huawei) , I try to disable the prox arp(it is disabled by default), but it will still work for NAT, I use Wireshark to capture the package, I found the interface still do the Prox-arp resond.

By: lee

lee — Mon, 26 Dec 2022 16:15:57 +0000

In reply to packetx. i do not about Cisco ,but if it is sure, it is the same as this: create a sub/sec IP address,in this case 72.3.4.55/32(must different from the interface IP mask), then the interface will do the gratuitous ARP, so let the network know the arp info

By: Ed Harmoush

Ed Harmoush — Thu, 05 May 2022 15:18:42 +0000

In reply to SHerlock. Proxy ARP is being used to instruct the upstream router (C, in my illustration) that packets sent to 72.3.4.55 should be sent to the MAC address of the Firewall.

By: SHerlock

SHerlock — Wed, 27 Apr 2022 06:13:08 +0000

can we say local proxy arp works here because the ARP request is for another IP of the same subnet that is 72.3.4.55.

By: Ed Harmoush

Ed Harmoush — Tue, 26 Apr 2022 20:46:06 +0000

In reply to Robert McCain. Thank you for the kind words. How did the Interviews go =) ?

By: Ed Harmoush

Ed Harmoush — Tue, 26 Apr 2022 20:45:45 +0000

In reply to John. Hi John. Thanks for the kind words =). Glad you enjoy this content. I think we answered your question on Discord. If you have any further, feel free to post there =). Cheers.

By: John

John — Thu, 21 Apr 2022 23:03:24 +0000

Hi Ed, first I want to congratulate you for your amazing articles, I’m impressed with the didactics, and I put practicalnetworking in my TOP1. I’m not an expert in Computer Networks and I just started marathoning your articles to learn about this amazing world of Computer network. I have a question and if you can answer me. I think I’m confusing the process of the AND technique of a Local Address and a Remote Address, but I’ll ask anyway. Does Host B know that the Remote IP Address has a /24 CIDR? I say this because if Host B knew that Host D’s IP Address is a /24 it would know that 10.0.4.44 is not in its local network using the AND technique that compares the mask with the IP Address to find out what it is network and what is host. In this case “Host B” does not know the CIDR of the Remote IP Address and does it believe that the address 10.0.4.44 is a Class A /8 or Class B /16 address? Is that why “host B” will consider that the IP address “10.0.4.44” to be in the range 10.0.0.0– 10.0.255.255 and therefore it is on its local network? The “Host B” would know with from CIDR using AND technique that Local IP Address 10.0.0.22/16 cannot communicate with Remote IP Address 10.0.4.44/24 even though if the range of IP Address 10.0.0.22/16 goes from 10.0.0.0 untill 10.0.255.255

By: Robert McCain

Robert McCain — Wed, 17 Nov 2021 14:06:58 +0000

I’m currently studying for Google and Amazon Security Engineering interviews. This tutorial series is straight gold, thank you.