Configure ospf

If it detects that there is a change to a LSA that would be flooded to the restarting router, or if there is a changed LSA on the retransmission list of the restarting router when the graceful restart process is initiated. The graceful-restart helper mode is enabled by default. Configuring Graceful Restart Wait Timer for OSPF OSPF routers are expected to set the RS-bit in the EO-TLV attached to a Hello packet when it is not known that all neighbors are listed in the packet, but the restarting routers require to preserve their adjacencies. However, the RS-bit value must not be longer than the RouterDeadInterval seconds. Hence the timers nsf wait command is introduced to set the RS-bit in Hello packets lesser than RouterDeadInterval seconds. The default value of NSF wait timer is 20 seconds. Before you begin To configure Cisco NSF wait time for OSPF, the device must be NSF-aware or NSF-capable. Procedure Step 1 Enter into OSPF router configuration mode. Example: ciscoasa(config)# router ospf Step 2 Enter timers and specify nsf. Example: ciscoasa(config-router)# timers?router mode commands/options: lsa OSPF LSA timers nsf OSPF NSF timer pacing OSPF pacing timers throttle OSPF throttle timersciscoasa(config-router)# timers nsf ? Step 3 Enter the graceful restart wait interval. This value can range between 1 and 65535. Example: ciscoasa(config-router)# timers nsf wait 200 By using the graceful restart wait interval, you can ensure that the wait interval is not longer than the router dead interval. Remove the OSPFv2 Configuration Remove the OSPFv2 configuration. Procedure Remove the entire OSPFv2 configuration that you have enabled. clear configure router ospf pid Example: ciscoasa(config)# clear configure router ospf 1000 After the configuration is cleared, you must reconfigure OSPF using the router ospf command. Remove the OSPFv3 Configuration Remove the OSPFv3 configuration. Procedure Remove the entire OSPFv3 configuration that you have enabled: clear configure ipv6 router ospf process-id Example: ciscoasa(config)# clear configure ipv6 router ospf 1000 After the configuration is cleared, you must reconfigure OSPFv3 using the ipv6 router ospf command. Example for OSPFv2 The following example shows how to enable and configure OSPFv2 with various optional processes: To enable OSPFv2, enter the following commands: ciscoasa(config)# router ospf 2ciscoasa(config-rtr)# network 10.0.0.0 255.0.0.0 area 0 (Optional) To redistribute routes from one OSPFv2 process to another OSPFv2 process, enter the following commands: ciscoasa(config)# route-map 1-to-2 permitciscoasa(config-route-map)# match metric 1ciscoasa(config-route-map)# set metric 5ciscoasa(config-route-map)# set metric-type type-1ciscoasa(config-route-map)# router ospf 2ciscoasa(config-rtr)# redistribute ospf 1 route-map 1-to-2 (Optional) To configure OSPFv2 interface parameters, enter the following commands: ciscoasa(config)# router ospf 2ciscoasa(config-rtr)# network 10.0.0.0 255.0.0.0 area 0ciscoasa(config-rtr)# interface insideciscoasa(config-interface)# ospf cost 20ciscoasa(config-interface)# ospf retransmit-interval 15ciscoasa(config-interface)# ospf transmit-delay 10ciscoasa(config-interface)# ospf priority 20ciscoasa(config-interface)# ospf hello-interval 10ciscoasa(config-interface)# ospf dead-interval 40ciscoasa(config-interface)# ospf authentication-key ciscociscoasa(config-interface)# ospf message-digest-key 1 md5 ciscociscoasa(config-interface)# ospf

Used to identify a specific device within an OSPF database. No two routers in an OSPF system can have the same router-id. If a router-id is not configured manually in the OSPF routing process the router will automatically configure a router-id determined from the highest IP address of an active interface. When configuring a router-id, the neighbors will not be updated automatically until that router has failed or the OSPF process has been cleared and the neighbor relationship has been re-established. Manually Configure OSPF Router-ID This section describes how to manually configure router-id in OSPFv2 process on the ASA. Procedure Step 1 To use a fixed router ID, use the router-id command. router-id ip-address Example: ciscoasa(config-router)# router-id 193.168.3.3 Step 2 To revert to the previous OSPF router ID behavior, use the no router-id command. no router-id ip-address Example: ciscoasa(config-router)# no router-id 193.168.3.3 Router ID Behaviour while Migrating While migrating OSPF configuration from one ASA , say ASA 1 to another ASA, say ASA 2, the following router id selection behaviour is observed: ASA 2 does not use any IP address for OSPF router-id when all interfaces are in shutdown mode. The possibilities for configuring router-id when all interfaces are in "admin down" state or shutdown mode are: If ASA 2 does not have any router-id configured before, you would see this message: %OSPF: Router process 1 is not running, please configure a router-id After the first interface is brought up, ASA 2 will take IP address of this interface as router id. If ASA 2 had router-id configured before and all interfaces were in "admin down" state when "no router-id" command was issued, ASA 2 will use old router id. ASA 2 uses the old router id, even if IP addresses on the interface that is brought up is changed, until "clear ospf process" command is issued. ASA 2 uses new router id, when ASA 2 had router-id configured before and at least one of interfaces were not in "admin down" state or shutdown mode when "no router-id" command was issued. ASA 2 will use new router id from the IP address of the interfaces even when interfaces are in "down/down" state. Configure OSPF Fast Hello Packets This section describes how to configure OSPF Fast Hello Packets. Procedure Step 1 Configure an interface: interface port-channel number Example: ciscoasa(config)# interface port-channel 10 The number argument indicates the port-channel interface number. Step 2 Set the interval during which at least one hello packet must be received, or else the neighbor is considered down: ospf dead-interval minimal hello-multiplier no.of times Example: ciscoasa(config-if)# ospf dead-interval minimal hell0-multiplier 5ciscoasa The no. of times argument indicates the number of hello packets to be sent every second.

The OSPF dynamic routing protocol is probably the most popular LAN routing protocol today. OSPF can scale to the largest LANs but can also start out small. While OSPF can be complex to configure, its basic configuration isn’t difficult. Let’s learn how to configure OSPF in the Cisco IOS.What do you need to know about OSPF?Before you configure OSPF, there are three things you should know about it first. Here they are:OSPF stands for open shortest path first. It also uses the SPF (shortest path first) algorithm to determine the best route to its neighbors.OSPF is a standard routing protocol, as defined by RFC2328 and RFC1247. This means that OSPF can run on just about any company’s’ routers and OSPF routes from a non-Cisco router can be exchanged with Cisco routers.The administrative distance for OSPF is 110.The entire network that OSPF routes for is called an "Autonomous System", or "AS".All OSPF routing updates must traverse area 0. Because of this, you should carefully design your network before you begin deploying OSPF.With OSPF, every router has its own unique "picture" (topology map) of the network. Routers use "HELLO" packets to periodically check with routers to ensure they are still there. Every router in OSPF is identified with a "router ID". The router ID can be manually entered or OSPF will automatically choose the IP address with the highest number.What features does OSPF offer?OSPF offers the following features, that are found in a number of routing protocols:A standards-based routing protocol that works is very interoperable between different vendors routers and firewallsSupports variable length subnet masks (VLSM), making it a classless routing protocolsAuthentication of routing updates are supportedRoute redistribution is supported between different routing protocolsOSPF works well in point to point and point to multipoint, broadcast or non-broadcast configurationsOSPF also offers a number of OSPF-specific features such as stub areas, virtual links, and OSPF on demand circuits.How do you configure OSPF in the Cisco IOS?To configure OSPF in the Cisco IOS, just follow these steps:Set the bandwidth on your interfaces using the bandwidth command Router (config-if)# bandwidth XX (where XX signifies the bandwidth of the WAN connection)Start the OSPF routing process and specify your process number. The process number is an arbitrary number. It is recommended that the number match on all routers but it is not required. The process ID number does not have to be the AS number, although many people confuse that it is.Router (config)# router ospf {process-ID#}Next, instruct the router to advertise the networks that are directly linked to it by entering network statments with the area ID number for that network, like this:Router (config-router)# network {X.X.X.X} {Y.Y.Y.Y} area {z}In this example, the X.X.X.X is the network id of a network that is linked directly to the router. The Y.Y.Y.Y is the wildcard mask for that network. The wildcard mask is the inverse mask of the subnet mask. The "z" parameter is the area id number. For small networks, this can always be zero (0) but for larger networks,

Create the OSPFOpen Shortest Path First (OSPF) is a link-state routing protocol for IP networks and is based on the Shortest Path First (SPF) algorithm. instance and enter the OSPF router configuration context. From this, you can proceed with other OSPF configuration tasks. Prerequisites You must be in the global configuration context, as indicated by the switch(config)# prompt to create the OSPF instance and enter the OSPF router configuration context. To configure a router ID, create OSPF network areas, or adjust other global OSPF configuration items, you must be in the router configuration context, as indicated by the switch(config-router)# prompt. Procedure Create the OSPF instance and enter the OSPF router configuration context using the following command. For command details, see router ospf. router ospf [vrf ] For example, the following command creates OSPF instance 1. switch(config)# router ospf 1switch(config-ospf-1)# Configure a global router ID using the following command. For command details, see router-id . router-id For example, the following command sets the router ID to 1.1.1.1. switch(config-ospf-1)# router-id 1.1.1.1 Optionally, if the OSPF process was disabled (it is enabled by default), enable the OSPF process using the following command. enable For command details, see enable . (Refer to disable for disabling the OSPF process).