OSPF

Configuration Example Configuring an Ospf Nssa

In Figure 2-4, Routers C and D are running RIP Version 2. Router D is advertising the networks 156.26.32.0 24 and 156.26.33.0 24 to Router C via RIP. Router C will redistribute the RIP routes, including the 10.1.1.8 30 network, into OSPF. Because Area 1 has been defined as an NSSA, the redistributed RIP routes will be advertised into Area 1 as OSPF type 7 routes. Initially you will configure Area 1 as a normal OSPF area in order to see the routes that are advertised. redistribute connected...

Configuration Example Advertising an Ospf Nssa Default Route into an Ospf Nssa

In Figure 2-5, Routers C and D are running RIP Version 2. Router D is advertising the networks 156.26.32.0 24 and 156.26.33.0 24 to Router C via RIP. Router C will redistribute the RIP routes, including the 10.1.1.8 30 network, into OSPF. Because Area 1 has been defined as an NSSA, the redistributed RIP routes will be advertised into Area 1 as OSPF type 7 routes. Initially, you will configure Area 1 as a normal OSPF area in order to see the routes that are advertised. redistribute connected...

Configuration Example Preventing Redistributed Routes from Entering an Ospf Nssa

In Figure 2-6, Routers C and D are running RIP Version 2. Router D is advertising the networks 156.26.32.0 24 and 156.26.33.0 24 to Router C via RIP. Router C will redistribute the RIP routes, including the 10.1.1.8 30 network, into OSPF. Routers B and E are running EIGRP. Router B will redistribute the EIGRP routes into OSPF. Since Area 1 has been defined as an NSSA, the redistributed RIP and EIGRP routes will be advertised into Area 1 as OSPF type 7 routes. Initially, you will configure Area...

Configuration Example Adjusting the Administrative Distance to Influence Route Selection

In Figure 6-1, Router B is receiving the route 3.3.3.0 24 from Router A via OSPF and Router C via EIGRP. Because EIGRP has a lower administrative distance than OSPF, the EIGRP route will be installed in the routing table on Router B. A loopback address on Routers A and C is used to simulate the network that is being propagated by OSPF and EIGRP. The ip ospf network point-to-point interface command (see Section 19-17) on Router A is used so the loopback is advertised as a 24 network and not a 32...

Configuration Example 1 Adjusting the Administrative Distance of All Routes Learned from a Particular OSPF Neighbor

In Figure 6-2, Router B is receiving the route 3.3.3.0 24 from Router A via OSPF and Router C via EIGRP. Because EIGRP hasa lower administrative distance than OSPF, the EIGRP route will be installed in the routing table on Router B. A loopback address on Routers A and C is used to simulate the network that is being propagated by OSPF and EIGRP. The ip ospf network point-to-point interface command (see Section 19-7) on Router A is used so the loopback is advertised as a 24 network and not a 32...

Figure 1910 An NBMA Network Is Typically Configured as a Broadcast Network when the OSPF Routers Are Fully Meshed and

Ip address 10.1.1.1 255.255.255.248 encapsulation frame-relay frame-relay map ip 10.1.1.2 101 broadcast frame-relay map ip 10.1.1.3 102 broadcast no frame-relay inverse-arp frame-relay Imi-type ansi ip address 10.1.1.2 255.255.255.248 encapsulation frame-relay frame-relay map ip 10.1.1.1 110 broadcast frame-relay map ip 10.1.1.3 112 broadcast no frame-relay inverse-arp frame-relay Imi-type ansi network 2.2.2.2 0.0.0.0 area 2 network 10.1.1.0 0.0.0.7 area 0 ip address 10.1.1.3 255.255.255.248...

Show ip ospf processid interface intname intnumber

The range of values is 1 to 4,294,967,295. int-name Interface name. int-number Interface number. Purpose To display information regarding OSPF-enabled interfaces. An OSPF process ID can be used if more than one OSPF process is active using the form show ip ospf process-id interface. The output of this command can be filtered, using regular expressions, by one of the following forms show ip ospf interface begin regular-expression show ip ospf interface exclude...

Ospf From Start To Expert

I have been involved with the world of networking from many directions. My experiences in education, network consulting, service provider support, and certification have shown me that there is a common thread that frustrates people in all of these arenas. That common thread is documentation. There are many factors that cause documentation to be frustrating but the most common are amount, clarity, and completeness. The amount of documentation available, especially in regards to OSPF, can be...

Area areaid nssa noredistribution

This value can be entered as a decimal number in the range of 1 to 4,294,967,295 or in IP address form in the range 0.0.0.1 to 255.255.255.255. Area 0 can be entered but Area 0 cannot be configured as an NSSA. Purpose In a stub or totally stubby area, the ABR to the stub area will prevent OSPF external routes (type 5) from being advertised into the stub area. This implies that an ASBR cannot be part of a stubby or totally stubby area because an ASBR generates OSPF...

Verification

Verify that Area 1 has been configured as an NSSA. rtrB show ip ospf Routing Process ospf 1 with ID 2.2.2.2 Supports only single TOS(TOSO) routes It is an area border and autonomous system boundary router Redistributing External Routes from, eigrp 1, includes subnets in redistribution SPF schedule delay 5 sees, Hold time between two SPFs 10 sees This document was created by an unregistered ChmMagic, please go to http www.bisenter.com to register it. Thanks Minimum LSA interval 5 sees. Minimum...

Configuration Example 5 Controlling Route Redistribution Based on Tag Values

In Figure 14-4, Router B is learning six routes via EIGRP. The EIGRP routes are redistributed into OSPF with the classful routes assigned a tag of 2 and the classless routes a tag of 1. Router A is redistributing the OSPF external routes into RIP-2. The policy is to redistribute only the classless routes into RIP-2. This can be accomplished using a route map and an IP access list. Because the external routes have been tagged, a route map can be used that redistributes only routes with a tag...

Show ip ospf processid database summary

The range of values is 1 to 4,294,967,295. router-id The OSPF router ID of the advertising router. asbr-id The OSPF router ID of the ASBR. Purpose To display information contained in the OSPF database. An OSPF process ID can be used if more than one OSPF process is active, using the form show ip ospf process-id database. The output of this command can be filtered, using regular expressions, by one of the following forms show ip ospf database begin...

Configuration Example Preventing Routes Redistributed into OSPF from Being Installed in the OSPF Database

In Figure 7-9, Router B is receiving the EIGRP routes 10.1.1.4 30, 3.3.3.0 24, and 4.4.4.0 24 from Router C. Router B is redistributing EIGRP into OSPF, and these routes will be advertised to Router A as OSPF external type 2 routes. Start by configuring Routers A, B, and C as shown in the listing that follows the figure. Figure 7-9. A Distribute List Prefix List Prevents Redistributed Routes from Being Installed in the Figure 7-9. A Distribute List Prefix List Prevents Redistributed Routes from...

Distance administrativedistance sourceipaddress sourceipmask accesslistnumber

administrative-distance The supplied value will be applied to the administrative distance of selected OSPF routes in the local routing table. The default administrative distance for OSPF routes is 110. source-ip-address IP address of the source of the OSPF routes. For OSPF, the source address is the OSPF router ID. source-ip-mask IP mask for the source of the OSPF routes. access-list-number Standard IP access number used to determine which routes learned from the source will have their...

Configuration Example Globally Modifying OSPF Interface Costs

Configure the routers in Figure 3-1 using the default reference value of 100,000,000 to investigate the costs of the various interfaces. Figure 3-1. OSPF Cost Is Based on the Interface Bandwidth Figure 3-1. OSPF Cost Is Based on the Interface Bandwidth network 1.1.1.1 0.0.0.0 area 0 network 172.16.1.0 0.0.0.255 area 0 ip address 10.1.1.5 255.255.255.252 clockrate 64000 network 2.2.2.2 0.0.0.0 area 0 network 10.1.1.4 0.0.0.3 area 1 network 172.16.1.0 0.0.0.255 area 0 ip address 10.1.1.6...

Configuration Example Using a Route Map for Conditional Default Route Advertisement

In Figure 4-5, Router B is receiving the route 3.3.3.0 30 from Router C via EIGRP. This network will carry all default traffic from the OPSF domain. If this network is down then you don't want the traffic from the OSPF domain to be sent to Router C. A route map can be used on Router B to make a conditional advertisement of a default route. For this example, the condition will be the existence of the 3.3.3.0 30 in the IP routing table on Router B. Figure 4-5. When OSPF Advertises a Default...

Router ospf processid vrf name

The range of values is 1 to 65535. name VPN Routing Forwarding Instance (VRF) name. Routes learned by the OSPF process will be placed in the VRF instead of the global IP routing table. Purpose In a Multiprotocol Label Switching (MPLS) virtual private network (VPN) environment, this formof the OSPF router command is used to transfer VPN customer routes between the service provider and the VPN customer. In an MPLS VPN environment, there are three types of routers,...

Configuration Example Modifying the Cost of an OSPF Neighbor on a Pointto Multipoint Interface

The cost to reach an OSPF neighbor is, by default, the bandwidth of the network connecting the two neighbors divided into 100,000,000. In Figure 11-5, the bandwidth of the Frame Relay link is 2048 kbps. Therefore, the OSPF cost of the Frame Relay interfaces is 48 (100,000,000 2,048,000). The cost option of the neighbor command can be used to change the cost to reach the neighbor. The interface command ip ospf cost (see Section 19-3) can also be used to change this cost. Theneighbor cost command...

R6debug ip ospf adj

OSPF adjacency events debugging is on r6 clear ip ospf process 6w3d OSPF Interface LoopbackO going Down 6w3d OSPF 6.6.6.6 address 6.6.6.6 on LoopbackO is dead, state DOWN 6w3d OSPF Interface SerialO 1 going Down 6w3d OSPF 6.6.6.6 address 10.1.1.17 on SerialO 1 is dead, state DOWN 6w3d OSPF 1.1.1.1 address 10.1.1.18 on SerialO 1 is dead, state DOWN 6w3d OSPF-5-ADJCHG Process 1, Nbr 1.1.1.1 on SerialO 1 from FULL to DOWN, Neighbor Down Interface down or detached 6w3d OSPF Interface LoopbackO...

About the Technical Reviewers

Mike Bass has worked for 22 years in computer networking, the last 17 years at Sprint. Mike's networking experience began with mini-computer and mainframe networks and now consists of planning and design for distributed and peer-to-peer systems supporting voice, video, and data services. Mike is currently responsible for the introduction of new networking technologies to support Sprint internal associates. Brian Morgan, CCIE 4865, CCSI, is the Director of Data Network Engineering at Allegiance...

Configuration Example 1 Multipoint Hub with Pointto Point Spokes

OSPF views networks as being of one of three types A broadcast multiaccess network On a broadcast multiaccess network, all routers attached to the network have a direct communication link with all other routers on the network. Examples of a broadcast multiaccess network are Ethernet, Token Ring, and FDDI. When OSPF sends a protocol packet onto a broadcast multiaccess network, all OSPF routers on the network will receive the packet. A point-to-point network On a point-to-point network, only two...

R6clear ip ospf process

6w4d Inc retrans unit nbr count index 1 (0 1) to 1 1 6w4d Set Nbr 1.1.1.1 1 first flood info from 0 (0) to 623AA408 (303) 6w4d Init Nbr 1.1.1.1 1 next flood info to 623AA408 6w4d OSPF Start SerialO 1 1.1.1.1 retrans timer 6w4d Set idb next flood info from 0 (0) to 623AA408 (303) 6w4d OSPF Start SerialO 1 pacing timer 6w4d Create retrans unit 0x623B71 A8 0x623C5DE8 1 (0 1) 1 6w4d OSPF Set nbr 1 (0 1) retrans to 4504 count to 1 6w4d Set idb next flood info from 623AA408 (303) to 0 (0) 6w4d OSPF...

Configuration Example Preventing OSPF Learned Routes from Being Installed in the IP Routing Table

Router A is receiving the OSPF routes 2.2.2.2, 3.3.3.3, and 4.4.4.4 from Router B. Start by configuring Routers A and B as shown in the listing that follows the figure. Figure 7-7. A Distribute List Prefix List Controls Which OSPF Routes Are Transferred from the OSPF Database into the IP Routing Table Figure 7-7. A Distribute List Prefix List Controls Which OSPF Routes Are Transferred from the OSPF Database into the IP Routing Table IP noutirg tabia dislribute-lisl prelix lis)...

Configuration Example 1 Simple Password Authentication on an OSPF Network

In Figure 19-1, the serial link in Area 0 is not using authentication, but simple password authentication is employed on the Ethernet network. Start by configuring Routers A and B as shown in the following listing. Figure 19-1. OSPF Authentication Can Be Configured on Individual Networks Figure 19-1. OSPF Authentication Can Be Configured on Individual Networks network 10.1.1.0 0.0.0.3 area 0 network 172.16.1.0 0.0.0.255 area 0 network 1.1.1.1 0.0.0.0 area 1 network 10.1.1.0 0.0.0.3 area 0...

Configuration Example Unconditionally Advertising a Default Route into the OSPF Domain

Configure the routers in Figure 4-2 as shown in the following code. Figure 4-2. When OSPF Advertises a Default Route, the Advertising Router Becomes an ASBR. The default-information-originate always Command Will Unconditionally Advertise a Default Route Figure 4-2. When OSPF Advertises a Default Route, the Advertising Router Becomes an ASBR. The default-information-originate always Command Will Unconditionally Advertise a Default Route network 1.1.1.1 0.0.0.0 area 0 network 172.16.1.0 0.0.0.255...

Configuration Example Setting the OSPF Metric Type for a Default Route

Configure the routers in Figure 4-4 as shown in the following listing. network 1.1.1.1 0.0.0.0 area 0 network 172.16.1.0 0.0.0.255 area 0 ip address 10.1.1.5 255.255.255.252 clockrate 64000 network 2.2.2.2 0.0.0.0 area 0 network 172.16.1.0 0.0.0.255 area 0 Verify that Routers A and B have established an OSPF neighbor relationship, as shown here. Neighbor ID Pri State 2.2.2.2 1 FULL BDR Dead Time Address 00 00 30 172.16.1.2 Neighbor ID Pri State Dead Time Address Interface 1.1.1.1 1 FULL DR 00...

Area areaid stub

This value can be entered as a decimal number in the range of 0 to 4,294,967,295 or in IP address form in the range 0.0.0.0 to 255.255.255.255. Purpose In Figure 2-11. Area 1 has one exit point. Routers in Area 1 do not need to know the specific external routes that are being redistributed into OSPF by the ASBR. Therefore, Area 1 can be configured as a stub area and the ABR will advertise a default route into Area Figure 2-11. An OSPF Stub Area with One Exit Figure 2-11....

Configuration Example Setting the Maximum Number of Equal Cost Paths That OSPF Will Install in the IP Routing Table

Router A has two parallel equal-cost paths to the loopback network on Router B. By default, OSPF will install both paths in the IP routing table. Configure Routers A and B as shown in the following lines of code. Figure 10-1. OSPF Can Install Up to Six Parallel Equal-Cost Paths in the IP Routing Table Figure 10-1. OSPF Can Install Up to Six Parallel Equal-Cost Paths in the IP Routing Table ip address 10.1.1.1 255.255.255.252 clockrate 64000 network 10.1.1.0 0.0.0.3 area 0...

Configuration Example 2 Changing Keys and Passwords

For additional security, you may choose to periodically change your key and password. With clear-text authentication, when you change passwords there will be a loss of OSPF connectivity from the time you change the password on one end interface until you change the password on the other interfaces in the area. With MD5 authentication, you can configure a new key and password on an OSPF interface while leaving the old key and password in place. The old key and password will continue to be used...

Figure 23 External OSPF Routes Are Not Advertised into an OSPF Stub Area Interarea and External Routes Are Not

Ip address 10.1.1.5 255.255.255.252 clock rate 64000 network 10.1.1.0 0.0.0.3 area 1 network 10.1.1.4 0.0.0.3 area 0 ip address 10.1.1.6 255.255.255.252 router ospf 1 redistribute connected subnnets network 10.1.1.4 0.0.0.3 area 0 If you examine the IP routing table on Router A, you can see that all OSPF routes are being advertised into Area 1. rtrA show ip route Codes C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter...

Virtual Link

Network 10.1.1.0 0.0.0.3 area 0 network 1.1.1.1 0.0.0.0 area 0 ip address 10.1.1.2 255.255.255.252 interface Seriall ip address 10.1.1.5 255.255.255.252 clockrate 64000 router ospf 1 area 1 virtual-link 2.2.2.2 network 3.3.3.3 0.0.0.0 area 2 network 10.1.1.4 0.0.0.3 area 1 Verify that the virtual link is active and that all OSPF routes are being exchanged. Virtual Link OSPF_VLO to router 3.3.3.3 is up Run as demand circuit DoNotAge LSA allowed. Transit area 1, via interface Seriall, Cost of...

Defaultinformation originate always metrictype type

The cost of a type 1 route includes both the external cost of the redistributed route and the OSPF cost. The cost of a type 2 route only includes the external cost. The default is type 2. Purpose When a route is redistributed into OSPF, the route is assigned a metric that represents the cost of reaching that route from the ASBR. In Figure 4-4. the external cost of the default route is 1. This is the value the ASBR would assign to the default route...