From: Barr, Scott
[mailto:owner-nv-l@lists.us.ibm.com] On
Behalf Of Barr, Scott
Sent: Friday, October 08, 2004
8:03 AM
To: nv-l@lists.us.ibm.com
Subject: RE: [nv-l] how does
netmon interact with the ARP cache?
Keep in mind, netmon has a list of things
to check status on. If you only had one node discovered, and it was on a 1
second status poll (theoretical, don't really try that) it would notice much
faster than if it were on a 3 minute poll with 100 nodes.
Netmon would definately notice it up at the next schedule
poll of the device. There is a netmon command to dump the ping list (and the
SNMP list) to see if you are backing up on status polls or whether you've got
cycles to spare. The man page for netmon has the proper flag (netmon -a 11 / 12
are for ping lists) if you issue netmon -a 12 and then look at the netmon.trace
file, it will tell you how many nodes are in line to be pinged.
We've all observed the behavior you are describing, but it
is usually attributed to being anxious to see the node turn green again. Now,
if the status poll time passes, and the node doesn't turn green, then you do
have a problem. If you want to know when the next status poll for a node
occurs, use ovtopodump -rl <resourcename>.
If this is the case, then how come in my
simulations when I start an agent, and then netview notices its down, then I turn
it back up, if I ping it right away the object in netview changes status, if
not, it will eventually pick it up when “it feels like it”
From:
owner-nv-l@lists.us.ibm.com [mailto:owner-nv-l@lists.us.ibm.com] On Behalf Of Barr, Scott
Sent: Thursday, October 07, 2004
12:52 PM
To: nv-l@lists.us.ibm.com
Subject: RE: [nv-l] how does
netmon interact with the ARP cache?
The arp cache will only store the mac
address of the local router that is forwarding packets on behalf of the IP
address you are interested. The real mac address is not present in the arp
table on the router (unless by coincidence, the router has another interface
into the subnet where the device actually resides). I believe the same would be
true for the netview box’s arp cache – it’s going to reflect
the mac address of the device local to the NetView server (such as the local
router) that can reach the end device IP address.
Short answer: I don’t think arp
cache has anything to do with it. I could be wrong.
From: owner-nv-l@lists.us.ibm.com
[mailto:owner-nv-l@lists.us.ibm.com] On
Behalf Of Freeman, Michael
Sent: Thursday, October 07, 2004
12:25 PM
To: nv-l@lists.us.ibm.com
Subject: [nv-l] how does netmon
interact with the ARP cache?
I have noticed that if a device goes down, and then comes
back up before netmon “magically notices it”, if you ping the
device, the object status will change in NetView. I assume this is because
NetView is somehow monitoring the arp tables? We are using NetView 7.1.3 on Solaris
and I am kind of curious to know how netmon and the arp cache works. It seemed
like in my tests with my network simulator, If I took down 200 nodes, and then
brought them up before netmon’s polling cycle kicked in, that if I pinged
every one of them (with a script of course), about only 10 or so nodes would
immediately have their object status changed in NetView. How does netmon divvy
up the workload? Helper threads? Timeslicing ?
*** Note new e-mail address
--
Michael J. Freeman
Netco Government Services
mfreeman@netcogov.com
--