OSPF and IS-IS
OSPF and IS-IS simulations are identical with the following exceptions.
OSPF routing uses OSPF areas, if specified. By default all interfaces are assigned area zero.
IS-IS routing uses IS-IS levels, if specified. By default, all interfaces are set to Level 2. Interfaces can belong to Level 1, Level 2, or both. If both, then an alternate metric for Level 1 can also be specified. You can change these properties using the Advanced tab in an interface Properties dialog box.
OSPF Area Simulation
OSPF area membership can be specified per interface. The two interfaces on each circuit must belong to the same area. Area names can be any string. Area zero, the backbone area, must be denoted by ‘‘0’’, ‘‘0.0.0.0’’, or an empty string. WAE Design simulates the OSPF area routing configuration in which the areas import LSAs from the backbone. A demand from a source node to a destination node in a different area will only be routed if it can reach the destination by passing through the source area, directly to area zero, and from there directly to the destination area.
By default, all nodes in a single AS are assumed to belong to a single OSPF area. Nodes are assigned to areas, as follows.
If OSPF areas are not defined for interfaces, all nodes are assumed to be in the same area.
Each interface can be assigned to only one OSPF area. Note that each node can be assigned to one or more areas.
If a node has an interface in an OSPF area, the node is assigned to that area.
An Area Border Router (ABR) is a node belonging to both area 0 and other OSPF areas.
IS-IS Multi-Level Simulation
By default, IS-IS interfaces are assigned to Level 2, though you can assign them to Level 1 or to both Levels 1 and 2. (For instructions, see Setting IS-IS Multi-Level Simulation.)
The IGP metric defines the Level 1 metric for interfaces in Level 1, in Level 2, or in both Level 1 and 2 if these have equal metrics. However, you can change the Level 1 metric.
If an interface is in both Level 1 and Level 2 with uneven metrics, the IGP metric defines the Level 2 metric and the Level 1 metric defines the Level 1 metric.
The IS-IS level is listed in the ISIS Level column of the Interfaces table, and the Level 1 metric is listed in the Metric Level 1 ISIS column.
By default, all nodes in a single AS are assumed to belong to a single IS-IS level. Nodes are assigned to levels, as follows.
Each node can be assigned to one or more levels.
Two Level 1 nodes are placed in different areas if any route between them (under normal operation) passes through a Level 2 node.
A node is assigned to a single Level 2 area if there is at least one interface that is Level 2 or both Level 1 and Level 2.
A node is assigned to one of potentially multiple Level 1 areas if any interface is Level 1 or both Level 1 and Level 2.
An ABR is a node belonging to both the Level 2 area and another IS-IS area.
Setting IS-IS Multi-Level Simulation
Follow these steps to set IGP metrics, IS-IS levels, and Level 1 metrics.
Choose one or more interfaces. Right-click one and choose Properties, or double-click an interface.
To set the IGP metric, enter its value in the IGP metric field or choose it from the drop-down list.
To set IS-IS multi-level simulation, click the Advanced tab.