Specifications
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Cisco IGX 8400 Series Provisioning Guide, Release 9.3.3 and Later Releases
OL-1166-04
APPENDIX
A
Cisco IGX 8400 Series Feeder Nodes
About Tiered Networks
Tiered networks were introduced in Cisco WAN Switching Software Release 8.0 as an alternative
approach to building large networks. In a tiered network, you construct high-capacity node clusters at
primary points of presence (POPs) and place smaller capacity nodes at secondary and tertiary POPs.
Each node in a tiered network is identified as either a routing node or a feeder node.
Alternate Terminology
Tiered network—hierarchical network
Routing node—hub node
Feeder node—nonrouting node, feeder shelf, interface shelf
About Feeder Nodes
Used in tiered networks, a feeder node is a small switch that acts as an extension shelf, typically with
lower-bandwidth interfaces, for a larger switch.
Feeder nodes are usually colocated with a routing node and are unaware of the presence of other nodes
in the network. The routing nodes behave like any normal routing node, but they are also responsible for
selecting routes for connections that terminate on the attached feeder nodes.
As an example, a number of IGXs can be designated as feeder nodes and connected to a colocated
Cisco BPX 8600 series switch acting as a routing node in a large POP. Meanwhile, other IGXs or BPXs
may act as routing nodes in smaller POPs. This allows a large, high-capacity network to be built without
necessarily having a large number of routing nodes.
A feeder node:
• Expands the port capacity of a routing node.
• Has no routing capabilities, so the feeder node is not counted against the maximum number of
switches allowed in the network.
• Connects to a routing node by a single uplink, called the feeder trunk, through which all connections
must pass to enter the network core.
• May receive calendar information from the routing node and may store the virtual path identifier
and virtual channel identifier (VPI/VCI) information for the connections on the feeder. Otherwise,
the feeder is a passive, isolated device that has no visibility beyond the feeder trunk.