trieved. Each atTable entry associates an IP address with its corresponding MAC address. Considering Figure 10.4, when two or more (sub) networks are interconnected, packet routing requirements demand that a gateway/router sits between them. The gateway is informed of the MAC addresses of both subnets, and SO the union of all the gateways/routers of a network contains the association IP/MAC address for every host in the entire enterprise network. Drawbacks arise in using ARP because: Networked hosts that have never communicated with other peers are not present in the cache. Cached entries expire and so a host that has not communicated for some time may not have an entry in the ARP table. The cache can be refreshed to ensure that it has an entry for each active host. Before searching the ARP table, a host pings the hosts that belong to the known net- works. This operation "wakes up" the hosts and hence propagates their MAC addresses, so refreshing the ARP table. JLocator also keeps a persistent MAC address cache that is periodically refreshed. When the associated MAC/IP address is known, the MAC address must be associated with the physical location of the network ele- ment that it identifies. Once the position of a cable coming from a specified port is known, it is possible to localise a host at any given moment. This is broadly how JLocator finds the location of assets. This section has outlined some of the problems in existing approaches to asset localisation, explained the challenges in asset localisation and described an asset localisation implementation that is superior to many of the other solutions currently available. Configuration Management In this chapter, two of the latest configuration management implementations in the market are detailed. While describing front-end features, some implementation details will be given to help understand the back-end functionality of an OSS implementation. The first implementation to be discussed has an excellent API implementation, and some aspects of this feature are 