Solved

ARP Problems (Entires becoming Static)

Posted on 2006-10-28
2
235 Views
Last Modified: 2010-03-19
Hi guys!

Have a weird one here that I hope you can help me understand how and why the following would happen.

In a remote site, on one subnet, there are 8 machines.

All are MEANT to have connectivity to one another, and ideally they do.

However, one day, one machine (machine B) can contact all the other machines on this subnet EXCEPT for machine A.
Now, all machines other than machine B, can contact machine A.
From machine A, I can ping all other machines other than machine B.
From machine B, I can ping all other machines other than machine A.

What I found:

I jumped on to machine A, and issued the following command:

arp -a
To display the arp table.
I found an entry in here for machine B that was type STATIC.
All other entries were dynamic.

I removed this static entry by:

arp -d <machine B ip address>

After this, I had connectivity back between machine A and machine B.

Question:

I know you can manually add a static entry in the arp cache for a system.
However, this has NOT been done in this case, and we dont have any need to do this.
So, my question is, under what circumstances, how, and why, would an arp entry for a machine become static if it was

NOT manually added to the arp cache as static. It really has got me stumped. Would a switch have something to do

with this?

Thanks in advance.

Simon
0
Comment
Question by:Simon336697
2 Comments
 
LVL 1

Author Comment

by:Simon336697
ID: 17831275
Does anybody know something??
0
 
LVL 1

Accepted Solution

by:
NKAI earned 500 total points
ID: 17834048
Not sure if this answers your question but it may help

From
http://www.microsoft.com/technet/pro...n/netdiag.mspx,
"Sometimes, an ARP cache entry can become stale and communication cannot
occur again until the bad ARP cache entry expires. It is also possible
that a bad static ARP cache entry could have been placed on the machine
and would never expire. The ARP cache is naturally flushed at 2 and 10
minute intervals, so this operation is considered safe. Note: If your
organization relies on static ARP cache entries, make sure there is a
mechanism for adding the entries back in once this tool is run." I
couldn't find the registry entry that defines the expiration intervals,
so maybe they are hardcoded. Looks like if the OP had waited a few
minutes that the problem might have gone away. However, entries added
with the -s parameter in the arp command are static and do not expire
out of the ARP cache.
0

Featured Post

Windows Server 2016: All you need to know

Learn about Hyper-V features that increase functionality and usability of Microsoft Windows Server 2016. Also, throughout this eBook, you’ll find some basic PowerShell examples that will help you leverage the scripts in your environments!

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
ASA DHCP setup 5 30
E-mail delayed during DNS server reboot 8 39
Wireless scope on sever with DSL connection 9 24
Powerline adapter slow Mbps? 38 127
#Citrix #Citrix Netscaler #HTTP Compression #Load Balance
If your business is like most, chances are you still need to maintain a fax infrastructure for your staff. It’s hard to believe that a communication technology that was thriving in the mid-80s could still be an essential part of your team’s modern I…
Internet Business Fax to Email Made Easy - With  eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, f…
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.

832 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question