Dell PowerConnect W-IAP Remote Configuration Guide - Page 971

Overview of OSPF 29 All three networks have the same network address, 10.0.0.0. Without support for RFC 2328 Appendix E, an OSPF router uses the same link state ID, 10.0.0.0, for the LSAs for all three networks. For example, if the router generates an LSA with ID 10.0.0.0 for network 10.0.0.0 255.0.0.0, this LSA conflicts with the LSA generated for network 10.0.0.0 255.255.0.0 or 10.0.0.0 255.255.255.0. The result is multiple LSAs that have the same ID but that contain different route information. When Appendix E is supported, the router generates the link state ID for a network as follows. 1. Does an LSA with the network address as its ID already exist? • No - Use the network address as the ID. • Yes - Go to step 2. 2. Compare the networks that have the same network address, to determine which network is more specific. The more specific network is the one that has more contiguous one bits in its network mask. For example, network 10.0.0.0 255.255.0.0 is more specific than network 10.0.0.0 255.0.0.0, because the first network has 16 ones bits (255.255.0.0) whereas the second network has only 8 ones bits (255.0.0.0): • For the less specific network, use the networks address as the ID. • For the more specific network, use the network broadcast address as the ID. The broadcast address is the network address, with all ones bits in the host portion of the address. For example, the broadcast address for network 10.0.0.0 255.255.0.0 is 10.0.255.255. If this comparison results in a change to the ID of an LSA that has already been generated, the router generates a new LSA to replace the previous one. For example, if the router has already generated an LSA for network with ID 10.0.0.0 for network 10.0.0.0 255.255.255.0, the router must generate a new LSA for the network, if the router needs to generate an LSA for network 10.0.0.0 255.255.0.0 or 10.0.0.0 255.0.0.0. Dynamic OSPF activation and configuration OSPF is automatically activated when you enable it. The protocol does not require a software reload. You can configure and save the following OSPF changes without resetting the system: • All OSPF interface-related parameters (for example: area, hello timer, router dead time cost, priority, re-transmission time, transit delay) • All area parameters • All area range parameters • All virtual-link parameters • All global parameters • Creation and deletion of an area, interface or virtual link In addition, you can make the following changes without a system reset by first disabling and then re-enabling OSPF operation: • Changes to address ranges • Changes to global values for redistribution • Addition of new virtual links PowerConnect B-Series FCX Configuration Guide 929 53-1002266-01