The key to understanding the traditional OSPFv2 configuration shown in this first example is to understand the OSPF network command. In this case, the command matches all three interfaces shown for Router R3 the next topic explains why. However, the first two parameters-the ip_address and wildcard_mask parameter values of 10.0.0.0 and 0.255.255.255-need some explaining. The integer area numbers range from 0 through 4,294,967,295.)įor the specific command in Example 8-2, any matched interfaces are assigned to area 0. (Note that the area can be configured as either an integer or a dotted-decimal number, but this book makes a habit of configuring the area number as an integer. Then, for each matched interface, the router enables OSPF on those interfaces, discovers neighbors, creates neighbor relationships, and assigns the interface to the area listed in the network command. Speaking generally rather than about this example, the OSPF network command tells a router to find its local interfaces that match the first two parameters on the network command. Example 8-2 OSPF Single-Area Configuration on R3 Using One network Command router ospf 1 network 10.0.0.0 0.255.255.255 area 0 (The router command uses the process-id to distinguish between the processes.) The process-id does not have to match on each router, and it can be any integer between 1 and 65,535. This number just needs to be unique on the local router, allowing the router to support multiple OSPF processes in a single router by using different process IDs. First, the router ospf 1 global command puts the user in OSPF configuration mode, and sets the OSPF process-id. The beginning single-area configuration on R3, as shown in Example 8-2, enables OSPF on all the interfaces shown in Figure 8-2. ![]() (Not shown, switch S3 has configured trunking on the other side of that Ethernet link.) Example 8-1 IPv4 Address Configuration on R3 (Including VLAN Trunking) interface GigabitEthernet 0/0.341 encapsulation dot1q 341 ip address 10.1.3.1 255.255.255.128 The configuration enables 802.1Q trunking on R3’s G0/0 interface, and assigns an IP address to each subinterface. The upcoming example discusses more about this logic.įigure 8-2 Sample Network for OSPF Single-Area ConfigurationĮxample 8-1 shows the IPv4 addressing configuration on Router R3, before getting into the OSPF detail. The configuration does not name the interfaces on which OSPF is enabled, instead requiring IOS to apply some logic by comparing the OSPF network command to the interface ip address commands. Note that the configuration creates a routing process in one part of the configuration, and then indirectly enables OSPF on each interface. Step 4.(Optional) Use the passive-interface type number router subcommand to configure any OSPF interfaces as passive if no neighbors can or should be discovered on the interface.įor a more visual perspective on OSPFv2 configuration, Figure 8-1 shows the relationship between the key OSPF configuration commands. Step 3.Use one or more network ip-address wildcard-mask area area-id router subcommands to enable OSPFv2 on any interfaces matched by the configured address and mask, enabling OSPF on the interface for the listed area. Rely on an interface IP address (chooses the highest IP address of all working nonloopbacks) ![]() Use the interface loopback number global command, along with an ip address address mask command, to configure an IP address on a loopback interface (chooses the highest IP address of all working loopbacks) Use the router-id id-value router subcommand to define the router ID Step 2.(Optional) Configure the OSPF router ID by doing the following: ![]() Step 1.Use the router ospf process-id global command to enter OSPF configuration mode for a particular OSPF process.
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