Routing Administrative Distance is a feature originally used by Cisco routing to select the best path when two or more paths exist, using two or more protocols that can forward packets to a given destination. Because NetMRI is not a router, Routing Distance provides for two specific use cases:

• It determines the preferred protocol used for the NetMRI appliance for receiving and transmitting packets. For example, an appliance might reside on a network that runs both OSPF and RIP. The Cisco default administrative distance for OSPF is 110, and the administrative distance default for RIP is 120, making OSPF the ‘preferred’ routing protocol for forwarding network traffic. The lower the distance value, the more preferred or reliable the system considers the protocol.
• For Topology, Administrative Distance affects how Path Analysis conducts calculations between any two points in the network. Under Path Analysis, a path could use two or more dynamic routing protocols (BGP4 and OSPF, for example). The Routing Distance settings determine how NetMRI reports its analyzed paths, indicating the protocol that takes precedence in the analyzed path.

Under Routing Distance, the values used by NetMRI reflect the Cisco-defined default values. You can change these values for the local NetMRI appliance or Operations Center system. Changing these values only affects the local NetMRI appliance’s calculations for Path Analysis if the appliance is one of the endpoints or an intermediate node in a path being calculated.

To edit the administrative distance:

1. Go to the Settings icon > General Settings > Path Analysis.
2. Click in the cell in the Admin Distance column where you want to make changes, enter the new value, and then click outside the cell to save the changes.
   

Entering a value of 255 as the Admin Distance causes the protocol to be ignored by the device.

The Routing Distance feature also may be useful for Operations Centers and their associated Collectors.

Specifying Path Calculations

In a large network, more than one possible path may exist between two devices. You can control the number of path calculations performed for the same Source/Destination pair. The default number of simultaneous path calculations is 2 with a maximum value of 10.

To edit the number of calculated paths:

1. Go to the Settings icon > General Settings > Path Analysis.
2. In the corresponding field, select the number of calculated paths. Avoid setting this value to too high a number, as multiple active path calculations can affect performance.
3. Click Save.
4. In the Confirm dialog box, click Yes.