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Old 07-17-2009, 05:21 PM
Baldy2K Baldy2K is offline
Join Date: Jul 2009
Location: Chicago area
Posts: 17
Default Path Discovery across MPLS clouds

While exploring the Path analysis module I ran into an interesting behavior. I attempted a couple pf path discovery methods;

SNMP failed when it attempted to query my carriers PE router,

Traceroute was broken when the tool attempted from an ASA running 7.2 code. (it attempted to use straight IOS style I'm sure I missed something here)

So I made the attempt using live route table. This worked across my L2 MPLS network (transparent, makes sense) But again when it got to the MPLS cloud it attempted to get the routes from the upstream peer. (I'm sure there is a security tech cursing loudly somewhere in the carriers NOC) and as a result it failed.

So the basic question is, has anyone found a smooth method for path discovery across an MPLS environment where you only manage the CE devices?

Also using a traceroute from an endstation to the target did yield better results, but there are occasions where I won't have access from a system on the source network.

I would prefer that the route table method be reliable as it should (and did where there is no L3 obsfucation via MPLS) find ALL paths, an important aspect of problem identification and resolution.

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Old 07-20-2009, 05:38 AM
David.C David.C is offline
Join Date: May 2009
Posts: 118
Default MPLS Path Discovery

Preview Qmap: "Path Discovery.qmap"

Hi Baldy2K:

On NetBrain Workstation, you can find a path across ISP’s MPLS network by adding an MPLS cloud.

To add an MPLS Cloud:

1. Right-click the MPLS Cloud node on the Network pane then select Add MPLS Cloud option to pop up the Add MPLS Cloud window.

2. Type a name, description in the corresponding fields.

3. Specify the CE and PE interface:
  • If your CE devices are connecting to PE using BGP, input BGP As Number of PE into the text box, then click the Create button, NetBrain will automatically discover all CE devices connected to the BGP AS you input.
  • Or click the Add button to pop up the Add CE Device window, and then specify the CE interface, routing protocol running on that interface, and IP address of the peering PE device.
4. Click OK button to finish the addition of the MPLS cloud and you can see the icon under the MPLS cloud node.

To generate virtual routing table for a MPLS cloud:

1. Drag a MPLS cloud onto a map, right-click the MPLS cloud and select Generate Virtual Routing Table menu.

2. Select a DataFolder which stores the live routing tables of CE devices. If there are no route tables on some CE devices, you can check the Retrieve from live network… checkbox.

Note: If you have checked the retrieve from live network option, please make sure that the CE devices are accessible.

3. Click OK button, NetBrain will generate the virtual routing table for the MPLS cloud based on the routes of CE devices.

To find a path across a MPLS cloud:

After adding a MPLS cloud and generating the virtual table, you can find the path via both live SNMP network discovery and cached routing tables.

Hope it helps
Attached Files
File Type: qmap Path Discovery.qmap (44.5 KB, 7 views)

Last edited by David.C; 07-20-2009 at 05:41 AM.
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Old 07-21-2009, 08:01 PM
Baldy2K Baldy2K is offline
Join Date: Jul 2009
Location: Chicago area
Posts: 17
Default Looks like that is what I'm missing

Caught this as I was headed out today, have some other issues that I'm working through, but that explains why it stopped and how to get around the problem... I generated the Virtual Table and will test some more tomorrow.

Thanks for the detailed response!
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Network Discovery

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