RBridge‘s are typically represented as a single node. An RBridge will use pseudonodes when there are multiple RBridges on the same link (i.e., shared Ethernet segment). Representing each link would require n(n-1) link database entries. Instead, each link is represented as a P2P link between pseudonodes, reducing the number of entries to (n-1)*2 entries. This improves database scaling by converting an N2 scaling problem into a linear scaling problem. Each RBridge can have up to 254 pseudonodes and is identified in the TRILL-ID by the appended octet to the RBridge MAC address.
Examining the RBridge topology shown below demonstrates how the use of pseudonodes reduces the number of links state database entries. If a pseudonode was not introduced, there would be 12 database entries. By introducing a pseudonode, as represented by the last octet value of 17, the number of database entries is reduced to six.
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