IS-IS Level 2 routing provisioning confirmation

Overview

TL1 RTRV-MAP-NETWORK commands can be used to confirm the area address and Level 2 router assignments of all nodes with OS LAN or DCC connectivity in a network.

Small networks

In a small network without IS-IS Level 2 Routing, the RTRV-MAP-NETWORK response includes the NSAPs (including the embedded area address field) of the local node and all remote nodes. This command may also be useful to confirm the uniqueness of the area addresses before combining two existing networks into one large network requiring IS-IS Level 2 Routing.

Large networks

In large networks with IS-IS Level 2 Routing, the RTRV-MAP-NETWORK response can vary based on whether or not the local node is a Level 2 router itself.

1. If the local node is not a Level 2 router, the response includes only remote nodes in the same OSI area as the local node and indicates which remote node is the default Level 2 router for the local node.

   The default Level 2 router is the node that the local node would rely on to route an OSI message outside the local NE's own area. When there are multiple Level 2 routers in the same area, not all nodes in the area would identify the same default Level 2 router typically.

2. If the local node is a Level 2 router, user input dictates whether the response includes:

   1. only remote nodes in the same OSI area as the local node (as in #1 above) but indicating which of those remote nodes are Level 2 routers

   2. all remote nodes that are Level 2 routers across all OSI areas.

Thus, with a RTRV-MAP-NETWORK command to one Level 2 router in each area, all nodes in a large network with IS-IS Level 2 Routing can be identified. One RTRV-MAP-NETWORK command at a time per area should suffice and is recommended to avoid unnecessarily burdening the network with many simultaneous or redundant TARP queries.

Problem isolation

TL1 command RTRV-MAP-NEIGHBOR may indicate and help resolve IS-IS Level 2 Routing provisioning mistakes. This command highlights any neighbors with which DCC is enabled but OSI communications is not fully functional. When addressed to a reachable node with an unreachable neighbor, this command identifies the NSAP area address and the Level 2 router status, if known, of the unreachable neighbor. The unreachable neighbor may simply have the wrong area address or both nodes may need to be enabled as Level 2 routers.

There is no standing alarm or status condition at a node with Level 2 router functionality enabled or disabled. There is no automatic means of determining whether the area address is consistent with the rest of the network. The user must confirm that all IS-IS Level 2 Routing rules have been followed to ensure successful OSI communications among the nodes in a network.