9tuts

9tuts.Step 1 Use the router ospfprocess-id global command to enter OSPF configuration mode for a specific OSPF process. (Optional) Configure the OSPF router by the following methodStep 2 Configure the OSPF router ID.a.Configure the router-id id-value router subcommand.b.Configure an IP address on a loopback interface (select the highest IP address on all available loopback interfaces). C,Depend on an interface IP address (select the highest IP address on all available non-loopback interfaces). Step 3 Configure one or more network ip-address wildcard-mask area area-id router subcommands. use any matching interface that has the OSPF process enabled and is assigned to the listed area. Step 4 (Optional) If no neighbors are or should be found on the OSPF interface, use the passive-interfacetype number interface subcommand to configure the interface as passive. Of these commands, only the OSPFnetwork command causes a lot of trouble. the OSPFnetwork command compares the first argument in the command with each IP address on the local router to try to find a match. However, instead of comparing the full number in thenetwork command with the full IPv4 address on the interface, the router can compare a group of octets based on an access control list (ACL)-style wildcard mask.a subset. For clarity, this list shows several network commands and describes the IP addresses that the command will match.176 Chapter 8 Implementing IPv4 OSPF network 10.1.1.1 0.0.0.0 area 0: matches exactly the interface with address 10.1.1.1 network 10.1.1.0 0.0.0.255 area 0: matches any interface whose address starts with 10.1.1 network 10.0.0.0 0.255.255.255 area 0: matches any interface whose address starts with 10 network 0.0.0.0 255.255.255.255 area 0: matches any interface configured with any IP address basically, if the wildcard mask value in the octet is 0, tells the IOS to compare to see if the numbers match, if the value is 255, then tells the IOS to ignore this octet when comparing numbers.Multi-area OSPFv2 Configuration ExampleBefore I discuss multi-area configuration, let me briefly mention the OSPF exam topic. Frankly, the OSPF exam topics (at the time of publication) cover the dividing line of whether you need to know how to configure multi-area OSPF (both OSPFv2 and OSPFv3). The configuration-oriented exam topics clearly indicate that only single-area configurations are covered, while the troubleshooting topics may imply that you need knowledge of multi-area configurations. The good news is: once you understand multi-area concepts and single-area configurations, adding multi-area configurations is extremely simple. So, this topic introduces the details of multiple areas in case you need them for the exam.This article then presents an example multi-region OSPF design based on the same three region design as the previous Figure 8-12. Figure 8-16 repeats the interconnection network topology and subnet IDs, and Figure 8-17 shows the zone design. Note that Figure 8-16 lists the last octet of each router's IPv4 address next to each interface, rather than the entire IPv4 address, to reduce confusion.10.1.23.0/24