Cisco 7206 Installation Guide - Page 48

Functional Overview Chapter 1 Product Overview MAC Address All LAN interfaces (ports) require unique MAC addresses, also known as hardware addresses. Typically, the MAC address of an interface is stored on a memory component that resides directly on the interface circuitry; however, the OIR feature requires a different method. For a description of OIR, refer to the "Online Insertion and Removal" section later in this chapter. The OIR feature allows you to remove a port adapter or service adapter and replace it with another identically configured one. If the new port adapter or service adapter matches the adapter you removed, the system immediately brings it online. In order to enable OIR, an address allocator with a unique MAC address is stored in an EEPROM on the router midplane. Each address is reserved for a specific port and slot in the router regardless of whether a port adapter or service adapter resides in that slot. The MAC addresses are assigned to the slots in sequence. The first address is assigned to slot 0, and the last address is assigned to slot 6. This address scheme allows you to remove port adapters and service adapters and insert them into other routers without causing the MAC addresses to move around the network or be assigned to multiple devices. Note that if the MAC addresses were stored on each port adapter or service adapter, OIR would not function because you could never replace one adapter with an identical one; the MAC addresses would always be different. Also, each time a port adapter or service adapter was replaced, other devices on the network would have to update their data structures with the new address. If the other devices did not update quickly enough, the same MAC address could 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 adapters and service adapters in the Cisco 7206 support online insertion and removal (OIR).This function allows you to install and replace port adapters 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 adapter or service adapter in a Cisco 7206 router, refer to the configuration note that ships with each port adapter or service adapter. Caution The network processing engine and the I/O controller are required system 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 will cause the router to shut down or crash, and might damage or destroy memory files. Each port adapter and service adapter has a bus connector that connects it to the router 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 adapter 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. For example, when you insert a port or service adapter, the longest pins make contact with the port or service adapter first, and the shortest pins make contact last. The system recognizes the signals and the sequence in which it receives them. 1-30 Cisco 7206 Installation and Configuration Guide OL-5102-02