Re: [nv-l] Re: [nv-l] Discovering networks without switches but with DHCP Nodes
2005-01-12 17:09:56
About discovery of remote subnets where
you don't have an snmp-enabled router:
Netview would normally discover things
from the arp cache of other things which are snmp-enabled. If you have
nothing there, you will have to force the discovery. You can do this in
a few ways. You can put the addresses, or names, in your seedfile. It will
do a pretty good job. It may get some subnet masks wrong, but it will tell
you about it (in netmon.trace) so you can delete them and rediscover them.
You can also run some sort of a pinger to ping them. If Netview hears from
them, it will add them if the seedfile allows it (eg there are no restrictions
in it for those addresses).
What you will get is a bunch of disconnected
subnets, since there are no routers to connect the subnets. This does not
affect Netview's ability to monitor their status.
About DHCP on the Unix platforms:
Netview on the Unix platforms does not
handle these in any useful way. On the Windows platform, you can tell it
in the seedfile that it is DHCP, and it will know what to do when it changes.
On the Unix platforms, it is possible that it will figure it out
based on changing name resolution, but not likely.
What most people do is exclude the DHCP
nodes from discovery, by specifying the addresses or address ranges in
the seedfile with a '!" in front of them so they are excluded. Since
they are probably desktop pc's, and they get turned off every afternoon,
no one wants them in the map where all they do is turn red. In your
case, since you want to monitor them, then you were better off on Windows.
If I had to try to make the Linux version handle DHCP nodes, I would
try:
1) make sure 'Node Down Delete' interval
is short for those address ranges, like 1 day. This is under Options...SNMP
Config'
2) make sure name resolution is dynamic
- that is, when a dhcp assignment changes, the name changes in your DNS
3) the configuration interval is short
for those address ranges, like 4 hours. This is also under Options...SNMP
config.
It is possible that normal name updating
will handle the deleting of the old addresses.
Something else I have tried when dealing
with DHCP nodes is to create a Netview Ruleset that listens for Interface
Added events, and invoke a script. That script can figure out if this added
interface is a DHCP one, and if there is already a down interface on that
node, and then the script can delete the old interface. That would be an
advanced topic, but it is something to think about if you can't come up
with anything else.
Cordially,
Leslie A. Clark
IBM Global Services - Systems Mgmt & Networking
(248) 552-4968 Voicemail, Fax, Pager
James Shanks/Raleigh/IBM@IBMUS
Sent by: owner-nv-l AT lists.us.ibm DOT com
01/12/2005 04:15 PM
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| Re: [nv-l] Re: [nv-l] Discovering
networks without switches but with DHCP Nodes |
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Camron,
Please don't send me personal notes. My replies have to be to the list.
Do you have SNMP enabled anywhere? NetView is an SNMP-manager and automatic
discovery is going to depend on reading the ARP caches of the devices you
have discovered, using SNMP, to find new devices. If you have no SNMP anywhere,
then you are going to have to populate your database manually using the
loadhosts command. But I thought you said that when you manually pinged
devices, then netmon added them to the map correctly. Are the subnet masks
correct or not? If not, then once again you will have to use loadhosts
to add new nodes, and you may very well have to delete the "bad"
once you have and load them afresh correctly, since without SNMP, netmon
would have no way to confirm that what he guessed as the subnet mask was
correct.
You can put not non-SNMP nodes in the seed file, but as the doc explains,
there is risk that they will be discovered with he wrong subnet mask since
netmon will have to guess at it.
The issue of DHCP is murkier, and not being the netmon expert, I'm not
certain what to say. Perhaps someone else will respond. But if your DHCP
nodes don't have SNMP, then I think we are going to have a hard time identifying
them as DHCP.
If you don't get the response your are looking for here, then I suggest
a call to IBM Support, so that you can get personalized help.
James Shanks
Level 3 Support for Tivoli NetView for UNIX and Windows
Tivoli Software / IBM Software Group
Camron
R <gundulf AT walla DOT com>
Camron R <gundulf AT walla DOT com>
Sent by: owner-nv-l AT lists.us.ibm DOT com
01/11/2005 11:54 AM
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Thanks, James.
But I still have questions:
1) Can I put not SNMP supported nodes on the seed file?
2) Can I use the same flagging of DHCP nodes from the seed file on Windows
version on the Linux version??
<jshanks AT us.ibm DOT com>
Re: [nv-l] Discovering networks without switches but with DHCP Nodes
If you and not going to enable SNMP on key
devices, so that netmon can do discovery for you, then you are going to
have to use a seed file.
You can read all about seed files in the NetView books (and there is much
about them in the archives as well). You did install the books didn't you?
Basically you will have to include seeds from each of your major sites,
and each of the switches/routers/gateways you want to monitor between them.
Seed files are also how you deal with DHCP nodes. These get flagged in
the seed file as well.
James Shanks
Level 3 Support for Tivoli NetView for UNIX and Windows
Tivoli Software / IBM Software Group |
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