Cisco 7200 VXR router User Manual page 61

Online Insertion and Removal
Note that if the MAC addresses were stored on each port adapter, OIR would not function
because you could never replace one port adapter with an identical one; the MAC addresses
would always be different. Also, each time a port adapter was replaced, other devices on
the network would have to update their data structures with the new address and, if they did
not do so quickly enough, could cause the same MAC address to appear in more than one
device at the same time.
Note Storing the MAC addresses for every slot in one central location means the addresses
stay with the memory device on which they are stored.
Online Insertion and Removal
All port and service adapters in the Cisco 7200 VXR routers support online insertion and
removal (OIR). This function allows you to install and replace port and service adapters
while the router is operating; you do not need to notify the software or shut down the system
power. This provides a method that is seamless to end users on the network, maintains all
routing information, and preserves sessions.
The following is a functional description of OIR for background information only; for
specific procedures for installing and replacing a port or service adapter in a Cisco 7200
VXR router, refer to the configuration note that ships with each port or service adapter.
The network processing engine and the I/O controller are required system
Caution
components that cannot be removed if the router is operating. Removing the network
processing engine or the I/O controller while the router is operating causes the router to shut
down or crash, and might damage or destroy memory files.
Each port or service adapter has a bus connector that connects it to the router's midplane.
Each midplane connector has a set of tiered pins in three lengths that send specific signals
to the system as they make contact with the port or service adapter. The system assesses the
signals it receives and the order in which it receives them to determine if a port or service
adapter is being removed or inserted into the midplane. From these signals, the system
determines whether to reinitialize a new interface or shut down a removed interface.
Cisco 7200 VXR Product Overview 1-51