Comments on: ARP Caching and Timeout

By: Brook Papworth

Brook Papworth — Tue, 15 Jan 2013 02:54:55 +0000

Very useful post – simple explanation of ARP as they relate to a Cisco environment with the ARP timeout value. Thank you!

By: locust

locust — Fri, 29 Jun 2012 11:40:08 +0000

@wbh, I know this is a bit late, but without Applications, a NIC will not send out frames, nor will it advertise its existence.

I’ve seen this many times, especially with “on-demand-only” devices like security cameras. They will literally sit on the network dead silent (unless they’re told to do things like update time via NTP or whatever) for days, months, YEARS. They still work, they’re perfectly fine. They’re just waiting on someone to call them up and ask for data.

They then spring to life as soon as you send a ping or other packet to their address, and MAC/ARP tables are populated.

The thing to remember is, if you send a packet to an IP that’s not listed in the ARP table, an ARP is broadcasted, which means every device on the LAN gets that frame, so it’s not necessary for the device to constantly tell the switch “Hey, I’m here, my MAC is blah blah blah.”

By: Ramesh

Ramesh — Sat, 24 Sep 2011 06:00:28 +0000

Nice artical. No use knowing latest technology wihout its basics. To make innovative thoughts we should be in comfortable with basics. I wish you to continue the same for different protocols as well.

Thank you once again.

Regards
Ramesh P

By: wbh

wbh — Thu, 25 Aug 2011 08:12:39 +0000

Very nice article .I have one question to ask. when a computer’s NIC is initiated ,how does it communicate with the switch to which it is attached .assume that no application programs want to send any frames to the switch, does the NIC sent its MAC and IP address to the switch in such a scenario?

By: floorripper

floorripper — Mon, 04 Apr 2011 10:30:38 +0000

I think that the article is very useful and clearly written.

Basics are very importatnt and we networkers tend fo forget the basics as we move on the CCNP or CCIP or another track as Voice and Wifi…
Companies like Amazon or Google will get you a hard time on the interviews about the basics.

Take care

By: CS

CS — Thu, 02 Dec 2010 20:21:22 +0000

Nice article, but the misspelled words take away from the message.

By: Amitesh

Amitesh — Tue, 29 Dec 2009 11:21:47 +0000

Nice Post, although basic but some people don’t care about basics