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3.6 Router-ID Anchoring Example ISO Pseudonode

3.6. Router-ID Anchoring Example: ISO Pseudonode​

Encoding of a broadcast LAN in IS-IS provides a good example of how

Router-IDs are encoded. Consider Figure 31. This represents a

Broadcast LAN between a pair of routers. The "real" (non-pseudonode)

routers have both an IPv4 Router-ID and IS-IS Node-ID. The

pseudonode does not have an IPv4 Router-ID. Node1 is the DIS for the

LAN. Two unidirectional links (Node1, Pseudonode1) and (Pseudonode1,

Node2) are being generated.

The Link NLRI of (Node1, Pseudonode1) is encoded as follows. The IGP

Router-ID TLV of the local Node Descriptor is 6 octets long and

contains the ISO-ID of Node1, 1920.0000.2001. The IGP Router-ID TLV

of the remote Node Descriptor is 7 octets long and contains the ISO-

ID of Pseudonode1, 1920.0000.2001.02. The BGP-LS attribute of this

link contains one local IPv4 Router-ID TLV (TLV type 1028) containing

192.0.2.1, the IPv4 Router-ID of Node1.

The Link NLRI of (Pseudonode1, Node2) is encoded as follows. The IGP

Router-ID TLV of the local Node Descriptor is 7 octets long and

contains the ISO-ID of Pseudonode1, 1920.0000.2001.02. The IGP

Router-ID TLV of the remote Node Descriptor is 6 octets long and

contains the ISO-ID of Node2, 1920.0000.2002. The BGP-LS attribute

of this link contains one remote IPv4 Router-ID TLV (TLV type 1030)

containing 192.0.2.2, the IPv4 Router-ID of Node2.

     +-----------------+    +-----------------+    +-----------------+
     |      Node1      |    |   Pseudonode1   |    |      Node2      |
     |1920.0000.2001.00|--->|1920.0000.2001.02|--->|1920.0000.2002.00|
     |     192.0.2.1   |    |                 |    |     192.0.2.2   |
     +-----------------+    +-----------------+    +-----------------+

                       Figure 31: IS-IS Pseudonodes
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