nv-l

Re: [nv-l] Routers in Isolated Subnet

2004-12-13 22:11:11
Subject: Re: [nv-l] Routers in Isolated Subnet
From: Leslie Clark <lclark AT us.ibm DOT com>
To: nv-l AT lists.us.ibm DOT com
Date: Mon, 13 Dec 2004 22:10:38 -0500

If I understand the question correctly, then in most cases James' description is accurate. For the routers between Netview and the subnet, you will get a Router Marginal event, which is meant to indicate that they have at least one interface up and one down, and that down one is a problem. For the remote subnet you get subnet unreachable, and for routers beyond that, you get Router Unreachable, meaning they are only victims. The Router Marginal events are therefore the most important ones. There will be Router Unreachable event, and yes, they indicate the impact of the Router Marginal problems.

There is a case in which you get a Router Marginal for a nearby router when it is blameless. For serial interfaces, when there is a remote failure, the nearby router will shut its end down in response. Netview will report that nearby router as Router Marginal, and the serial network as Network Unreachable and the remote, failing router as Router Unreachable. This suggests that the failure was an interface on the near router, when the problem was really the failure of the remote router.  This is probably not the case in the arrangement you are describing, however.

Is your concern that with RFI enabled you won't get the Node Down event for the servers on that subnet, and the servers are what you are really worried about? You kind of have to focus on the root cause events, the router problems, as a trade off for all of the event suppression you get with RFI.

If you have Switch Analyzer installed, it can generate an impact report for a given router or layer2 device.

I hope that throwing all of these words out there will help. If not, digest this and ask again.

Cordially,

Leslie A. Clark
IBM Global Services - Systems Mgmt & Networking
(248) 552-4968 Voicemail, Fax, Pager



James Shanks/Raleigh/IBM@IBMUS
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12/10/2004 10:18 AM
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Re: [nv-l] Routers in Isolated Subnet





I was hoping that someone with more experience with RFI would try to answer you on this, but since no one has, here's my two cents.

First, there is no list nor utility that will tell you what routers netmon currently thinks are unreachable. That might be nice enhancement to netmon someday, but it is not available today.

But, if you have a router (A) connected to a subnet, and you have another router (B) connected to that same subnet, and the only path to router B is across the subnet and out via router A, then if A has a problem, you should get
(a) either an Interface Down event if just the connecting interface is lost, and a Router Marginal for A, or
(b) a Router Down event for router A if the entire thing is lost.
But in either case you should get a Router Unreachable event for B, and a Subnet Unreachable event for the subnet between them. At least that is my understanding, though I must add that I don't work on netmon. If I have gotten this wrong, then perhaps someone else will correct me.

Now as for you admins, I have to ask why they are not planning to use the web client when they login from their remote location?
That's exactly what it is for, so you can use the map and all the attendant NetView functions from a remote location. All you need a is browser.
If they aren't going to do that, then the only thing I can think of for you to do to get a list of routers which are unreachable would be to either
(1) create a smartset for isRouter and IP Status Unreachable and then use nvUtil to query it
(2) create a report for the same thing using nvdbformat and run that
You could then email that to the admins, but putting it in a pager notice itself would likely make the message very large.

NetView has a map precisely so that operators can get an idea of the status of the network visually, so they can drill down and see the source of the problem, rather than be told about it descriptively. So I still think having them log in remotely via the web client is a much better idea. And I know other NetView users are doing exactly this. Some of their operators take a laptop with them wherever they go, just so they can log in from wherever they are when the pager goes off.

Anyone else?

James Shanks
Level 3 Support for Tivoli NetView for UNIX and Windows
Tivoli Software / IBM Software Group
Inactive hide details for SIXFC AT pjm DOT comSIXFC AT pjm DOT com

SIXFC AT pjm DOT com
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12/09/2004 12:22 PM
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[nv-l] Routers in Isolated Subnet




We have parallel paths between critical servers. If a router on one path is down, the admins will be notified. If a router on the second path goes down, they will also be notified. Additionally, with both paths down, the admins want to know what routers are now isolated. Will there be a router unreachable event for each one, following or preceding the subnet unreachable? How can we relate them to the source problem? Does RFI keep a list of the relationships or have a utility to determine them? Do I have access to it?

After a pager alert, these folks will most likely login from a remote location and open their e-mail. That's where we're trying to put the information and why we're not telling them to look at the map.

Thanks.
Chris Six

PJM Interconnection, llc

sixfc AT pjm DOT com

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