ARP Table Updating

Good morning,

I have a Dell 6248P/6248 Switch stack with 9 switches. I am actually learning as I go about routing and switching so please bear with me on my question.

We are in the process of putting VLAN's in and the individual that was helping out did a lot of things on his own and did not document everything. His access was removed by my boss so we can see exactly what has been done and why.

One of the VLAN's in question is the new VLAN 11 voice VLAN. We have moved 20 test users to this VLAN and are experiencing issues. When users in the regular VLAN from the flat network call users in the test VLAN 11 sometimes the call works perfectly and sometimes you can't hear one or the other. I did some reading and believe the ARP cache may not be working properly on the switches. Oh, I forgot to add we are using the switch stack to do the routing as they are layer 2/3 switches.

While investigating the ARP settings I found they were set to 6 hours. I chose to use the recommended 4 hours that Cisco uses. While watching the ARP table I am see the aging constantly resetting and none of them aging much more than 30 seconds. Is this normal for the ARP table to update that often?

Thanks in advance
newmanmeNetwork Administrator\EngineerAsked:
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Routers (layer 3) devices keep arp entries for up to 4 hrs, layer 2 devices keep arp information for 5 minutes, and end systems keep
arp information for ~20seconds. Keep in mind, that every time a device speaks on the network the arp entry is updated and the timer restarts. The timers above are typical for most device types but can be slightly different.

So depending on the device type this is normal behavior and is part of the overall ethernet network operation. As long as your devices are active the arp table should not be part of your problem, when active the arp cache is constantly updated. Perhaps bad design or incorrect configuration is the issue. Calling from one local vlan to another should not be a problem at all. Sounds liek there could be congestion and or packet loss somewhere, hard to tell with information available.

harbor235 ;}

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
newmanmeNetwork Administrator\EngineerAuthor Commented:
Thanks harbor235 that is an excellent explanation and helps me to better understand the ARP cache.
newmanmeNetwork Administrator\EngineerAuthor Commented:
excellent explanation that is easy to understand.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Switches / Hubs

From novice to tech pro — start learning today.