Description: The update sequence number in EIGRP (Enhanced Interior Gateway Routing Protocol) is an identifier that indicates the order in which routing updates are sent between routers using this protocol. Each time an EIGRP router sends an update, this number is incremented, allowing receiving devices to determine if they have the most recent information. This mechanism is crucial for maintaining the consistency and accuracy of the routing table in a network, as it ensures that routers can identify and discard outdated updates. The update sequence number also helps prevent routing loops and optimizes the convergence process, as routers can quickly recognize which information is valid and which is not. In summary, this number is fundamental to the efficient and effective operation of EIGRP, ensuring that routers operate with the most up-to-date and accurate information possible.
History: EIGRP was developed by Cisco in the 1990s as an enhancement of the Interior Gateway Routing Protocol (IGRP). The introduction of the update sequence number was part of efforts to improve efficiency and convergence speed in networks. As networks became more complex, the need for a protocol that could quickly adapt to changes became evident, leading to the creation of EIGRP as a more advanced and robust routing protocol.
Uses: The update sequence number is primarily used in networks implementing EIGRP to ensure that all routers have the most recent information about available routes. This is especially useful in environments where network topologies change frequently, as it allows routers to quickly react to changes and maintain network stability.
Examples: A practical example of the use of the update sequence number can be observed in a corporate network where multiple interconnected EIGRP routers are present. If one of the routers experiences a failure and restarts, it will send an update with a higher sequence number, allowing other routers to recognize that this is the most recent information and update their routing tables accordingly.
