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Importing GRE Tunnel Information from Router Configuration Files

Use these procedures if you have Cisco GRE tunnels configured in your network.

If you wish to perform this task, you should have a set of router configuration files with GRE tunnels configured.

Generic Routing Encapsulation (GRE) Tunnels can be either imported from the router configuration files, or created from the NorthStar Planner Graphical Interface for what-if studies. Afterwards, the GRE tunnel path and details can be viewed, as well as the details and paths of the demands routed over the GRE tunnel. The GRE tunnel can also be referenced as the next hop of a static routing table.

The following GRE statements are parsed during the config import:



NorthStar Planner maps these statements into entries in the intfmap (interface), tunnel, and bblink file.

Example intfmap entry

Example tunnel entry

In the tunnel entry, note that the tunnel source of Tunnel4 matches the destination IP address of Tunnel5, and the tunnel source of Tunnel5 matches the destination IP address of Tunnel4.

Example bblink entry

Each GRELINK entry references one GRE tunnel interface for the A to Z direction using C1=<interface> and one GRE tunnel interface for the Z to A direction using C2=<interface>. By default, the status of a link of type GRELINK will be down/deleted if one of the tunnels fails to be routed. If both tunnels are routed, the GRE link is considered to be up, and traffic over a GRELINK will then be routed over the links traversed by the GRE tunnel.

In some cases, however, the software fails to route the GRE tunnel due to incomplete information. In those cases, the GRELINK may actually be up but there is no information to determine whether the tunnels are successfully placed. For example, the the config files for the routers necessary to route the GRE tunnel may be missing if they belong to another service provider. To avoid setting the GRELINK status to down in this scenario, set virtualgrelink=0 in the dparam file to treat GRELINKs as normal links.

To import the router configuration files, select File>Import Data and follow the Import Network Wizard. Alternatively, you may run the getipconf program in text mode.

After importing the config files, view the Integrity Checks report by selecting Report > Report Manager and then selecting the Configuration Report>Summary of Integrity Checks Report item.

The “Asymmetric GRE tunnels” integrity check will appear if there is a GRE tunnel defined at one end of the tunnel but not the other. Additionally, the “Inconsistent GRE tunnels protocol” integrity check will appear if the IGP protocol defined on one end of the GRE tunnel is different than the IGP protocol defined on the other end. These integrity checks are included under the TUNNEL category. To view the details of an integrity check, right-click on the row and select Display item(s) for this msg ID/Category.