Configuring OSPF Area Parameters

Configuring Stub Area

A stub area is an area in which advertisements of external routes are not allowed, which thus reduces the size of the database even more. Instead, a default summary route (0.0.0.0) is inserted into the stub area in order to reach these external routes. If you have no external routes in your network, then you have no need to define stub areas.

Execute the following commands to configure an area as a stub area.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a stub area.

iS5comm(config-router)# area 0.0.0.6 stub

Note:

Execute the following command to reconfigure the area 0.0.0.6 as a normal area.

iS5comm(config-router)# no area 0.0.0.6 stub

Note:

For Sample Configuration for Stub area, ASBR and route redistribution, refer to Figure - Topology for Configuration of Stub area, ASBR and route redistribution.

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring ASBR Router

Routers that act as gateways (redistribution) between OSPF and other routing protocols (IGRP, EIGRP, RIP, BGP, Static) or other instances of the OSPF routing process are called autonomous system boundary router (ASBR).

Execute the following commands to configure a router as an ASBR router.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the ASBR router.

iS5comm(config-router)# asbr router

Note:

Disable the ASBR router by executing the following command

iS5comm(config-router)# no asbr router

Note:

For Sample Configuration for Stub area, ASBR and route redistribution, refer to Figure - Topology for Configuration of Stub area, ASBR and route redistribution.

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring Redistribution

Redistribution configures the protocol from which the routes have to be redistributed into OSPF.

Execute the following commands to configure redistribution.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the ASBR router.

iS5comm(config-router)# asbr router

Configure redistribution of all routes.

iS5comm(config-router)# redistribute all

Note:

Disable redistribution of routes by executing the following command.

iS5comm(config-router)# no redistribute all

Figure 1. Topology for Configuration of Stub area, ASBR and route redistribution

Sample Configuration for Stub area, ASBR, and route redistribution

Some prerequisite configuration (refer Configuration Guidelines (Prerequisite)) must be done in the switches ISS4, ISS5, and ISS7 before configuring OSPF.

Execute the following commands in ISS4, ISS5 and ISS7.

Type the following:

Configuration of ISS4

ISS4 is configured as an ASBR (Autonomous System Border Router) for redistributing the external routes into OSPF domain.

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# router-id 10.4.0.4

iS5comm(config-router)# asbr router

iS5comm(config-router)# redistribute all

iS5comm(config-router)# network 10.5.5.4 area 0.0.0.0

iS5comm(config-router)# exit

iS5comm(config)# ip route 100.0.0.0 255.0.0.0 10.5.5.5

iS5comm(config)# end

Configuration of ISS7

In ISS7, area 0.0.0.4 is configured as a stub area. External routes are not redistributed into the stub area.

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# router-id 10.8.0.7

iS5comm(config-router)# network 10.8.0.7 area 0.0.0.4

iS5comm(config-router)# area 0.0.0.4 stub

iS5comm(config-router)# exit

View the configuration details by executing the following show commands.

Type the following:

In ISS4

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask	TOS 	NextHop/Interface 	Cost Rt.Type	Area

---------	---	-------/--------- 	---- ------- 	----

10.5.5.0/255.255.255.0  0   0.0.0.0/vlan4     1	IntraArea 0.0.0.0

10.8.0.0/255.255.0.0    0   10.5.5.5/vlan4    2	InterArea 0.0.0.0

iS5comm# show ip ospf 0.0.0.0 database external

OSPF Router with ID (10.4.0.4)AS External Link States

-----------------------

LS age             : 300

Options LS: (No ToS Capability, DC)

Type: AS External Link

Link State ID: 10.5.5.0

LS Seq Number      : 0x80000001

Checksum : 0x2a6

Length             : 36

Network Mask       : 255.255.0.0

Metric Type       : 0x80

Metric            : 10

Forward Address   : 0.0.0.0

Externel Route Tag: 0

AS External Link States

----------------------

Advertising Router     : 10.4.0.4

LS Seq Number          :0x80000001

Checksum               : 0xbee3

Length                 : 36

Network Mask           : 255.255.255.0

Metric Type            : 0x80

Metric                 : 10

Forward Address: 0.0.0.0

Externel Route Tag: 0

AS External Link States

-----------------------

LS age	: 300

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 10.5.6.0

Advertising Router 	: 10.4.0.4

LS Seq Number	: 0x80000001

Checksum	: 0xb3ed

Length	: 36

Network Mask	:255.255.255.0

Metric Type	: 0x80

Metric	: 10

Forward Address	: 0.0.0.0

Externel Route Tag: 0

AS External Link States

-----------------------

LS age:   300

Options:  (No ToS Capability, DC)

LS Type:  AS External Link

Link State ID: 100.0.0.0

Advertising Router: 10.4.0.4

LS Seq Number Checksum: 0x80000001

Advertising Router : 0xcd6b

Length: 36

Network Mask: 255.0.0.0

Metric Type     : 0x80

Metric          : 10

Forward Address : 10.5.5.5 Externel Route Tag: 0

In ISS5

View the external routes are redistributed in this switch

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask			TOS 	NextHop/Interface	   Cost 	Rt.Type 	Area

---------			--- 	-------/---------	    ---- 	-------	----

10.4.0.0/255.255.0.0	 0	 10.5.5.4/vlan4	 10	 Type2Ext	 0.0.0.0

10.5.5.0/255.255.255.0	 0	 0.0.0.0/vlan4	 1 	IntraArea	 0.0.0.0

10.5.6.0/255.255.255.0 	0	 10.5.5.4/vlan4 	10 	Type2Ext	 0.0.0.0

10.8.0.0/255.255.0.0	 0	 0.0.0.0/vlan1 1	 IntraArea	 0.0.0.4

100.0.0.0/255.0.0.0	 0	 10.5.5.5/vlan4	 10	 Type2Ext		 0.0.0.0

iS5comm# show ip ospf 0.0.0.0 database external

OSPF Router with ID (10.8.0.5)

AS External Link States

LS age:   300

Options:  (No ToS Capability, DC)

LS Type:  AS External Link

Link State ID: 10.4.0.0

Advertising Router : 10.4.0.4 LS Seq Number	: 0x80000001 Checksum	: 0x2a6

Length	: 36

Network Mask	: 255.255.0.0

Metric Type	: 0x80

Metric	: 10

Forward Address	: 0.0.0.0

Externel Route Tag: 	0

AS External Link States

-----------------------

LS age	: 300

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 10.5.5.0

Advertising Router 	: 10.4.0.4

LS Seq Number	: 0x80000001 Checksum	: 0xbee3

Length	: 36

Network Mask	: 255.255.255.0

Metric Type	: 0x80

Metric	: 10

Forward Address	: 0.0.0.0

Externel Route Tag	: 0

AS External Link States

-----------------------

LS age	: 300

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 10.5.6.0

Advertising Router 	: 10.4.0.4

LS Seq Number	: 0x80000001

Checksum	: 0xb3ed

Length	: 36

Network Mask	: 255.255.255.0

Metric Type	: 0x80

Metric	: 10

Forward Address	: 0.0.0.0

External Route Tag	: 0

In ISS7

View the external routes are redistributed in this switch

iS5comm# show ip ospf route

OSPF Process Routing Table Dest/Mask		TOS	NextHop/Interface		Cost	Rt.Type	Area

---------		---	-------/---------		----	-------	----

0.0.0.0/0.0.0.0	 0	 10.8.0.5/vlan1	 2	 InterArea 	0.0.0.4

10.5.5.0/255.255.255.0	 0	 10.8.0.5/vlan1	 2	 InterArea	 0.0.0.4

10.8.0.0/255.255.0.0	 0	 0.0.0.0/vlan1	 1	 IntraArea	 0.0.0.4

iS5comm# show ip ospf 0.0.0.4 database external

OSPF Router with ID (10.8.0.7)

Configuring NSSA Area

An NSSA area has the capability to import limited number of external routes. Execute the following commands to configure an area as an NSSA (Not-So-Stubby-Area) area.

Execute the following commands to configure an area as an NSSA area.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

Note:

Execute the following command to reconfigure the area 0.0.0.6 as a normal area

iS5comm(config-router)# no area 0.0.0.6 nssa

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Note:

Refer to Sample NSSA Configuration, summary address configuration, and area-default cost.

Configuring Summary Address

Execute the following commands to configure a summary address.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

Configure the summary address for 90.0.0.0/8 in the NSSA area.

iS5comm(config-router)# summary-address 90.0.0.0  255.0.0.0 0.0.0.6

Note:

Delete the summary address configuration for 90.0.0.0/8 in the NSSA area by executing the following command

iS5comm(config-router)# no summary-address 90.0.0.0  255.0.0.0 0.0.0.6

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring Area-default Cost

Configuring Area-default Cost specifies the cost for the default summary route sent into a stub or NSSA.

Execute the following commands to configure the Area-default Cost.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

iS5comm(config-router)# area 0.0.0.6 default-cost 50.

iS5comm(config-router)# area 0.0.0.6 default-cost 50

Note:

Go back to default cost for the default summary route sent into NSSA area by executing the following command.

iS5comm(config-router)# no area 0.0.0.6 default-cost

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Sample NSSA Configuration, summary address configuration and area- default cost

Figure 2. Sample NSSA Configuration, summary address configuration and area- default cost

Configuring ISS2, ISS4 and ISS9

Some prerequisite configuration (refer to section 3.2 Configuration Guidelines (Prerequisite)) must be done in the switches ISS2, ISS4, ISS9 before configuring OSPF.

Execute the following commands in ISS2, ISS4 and ISS9.

Type the following:

Configuration of ISS2

ISS4 is configured as an ASBR (Autonomous System Border Router) for redistributing the external routes into OSPF domain.

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# router-id 10.4.0.4

iS5comm(config-router)# network 10.4.0.2 area 0.0.0.0

iS5comm(config-router)# network 10.2.2.2 area 0.0.0.2

Configure the area 0.0.0.2 as a NSSA area.

iS5comm(config-router)# area 0.0.0.2 nssa

iS5comm(config-router)# end

Configuration of ISS4

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# router-id 10.4.0.4

iS5comm(config-router)# network 10.4.0.4 area 0.0.0.0

iS5comm(config-router)# end

Configuration of ISS9

iS5comm# configure terminal

iS5comm(config)# router ospf

Configure ASBR status and redistribute static routes into the OSPF domain.

iS5comm(config-router)# asbr router

iS5comm(config-router)# redistribute static

iS5comm(config-router)# router-id 10.2.2.9

iS5comm(config-router)# network 10.2.2.9 area 0.0.0.2

Configure the area 0.0.0.2 as an NSSA area.

iS5comm(config-router)# area 0.0.0.2 nssa

Configure summary address for the range 90.0.0.0/8 in the area 0.0.0.2.

iS5comm(config-router)# summary-address 90.0.0.0  255.0.0.0 0.0.0.2

iS5comm(config-router)# exit

Configure static routes.

iS5comm(config)# ip route 90.1.0.0	255.255.0.0	10.2.2.2

iS5comm(config)# ip route 90.2.0.0	255.255.0.0	10.2.2.2

iS5comm(config)# ip route 90.3.0.0	255.255.0.0	10.2.2.2

iS5comm(config)# ip route 90.4.0.0	255.255.0.0	10.2.2.2

iS5comm(config)# ip route 90.5.0.0	255.255.0.0	10.2.2.2

iS5comm(config-router)# end

Viewing the configuration details of ISS2, ISS4, and ISS9

Execute the following commands in ISS2, ISS4 and ISS9.

Type the following:

In ISS2

View the two NSSA-external LSAs, one for 90.0.0.0/8 matching the summary range configured and the other for the default external route in the NSSA area.

Another external LSA is generated in the area 0.0.0.0 corresponding to the NSSA-external LSA 90.0.0.0/8.

iS5comm# show ip ospf database nssa-external

OSPF Router with ID (10.4.0.2)

---------------------------------------------

LS age	: 300

Options	: (No ToS Capability, DC)

NSSA External Link States (Area 0.0.0.2)

LS Type	: NSSA External Link

Link State ID	: 90.0.0.0

Advertising Router 	: 10.2.2.9

LS Seq Number	: 0x80000001

Checksum	: 0xc84f

Length	: 36

NSSA External Link States (Area 0.0.0.2)

LS age	: 300

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 0.0.0.0

Advertising Router : 10.4.0.2

LS Seq Number	: 0x80000002

Checksum	: 0x120

Length	: 36

iS5comm# show ip ospf database external

OSPF Router with ID (10.4.0.2)

AS External Link States

---------------------------------------------

LS age: 0

Options:  (No ToS Capability, DC)

LS Type:  AS External Link

Link State ID: 90.0.0.0

Advertising Router 	: 10.4.0.2

LS Seq Number	: 0x80000001

Checksum	: 0x49fd

Length	: 36

Network Mask	: 255.0.0.0

Metric Type	: 0x80

Metric	: 10

Forward Address	: 10.2.2.9

External Route Tag: 0

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask			 TOS 	NextHop/Interface	   Cost 	Rt.Type 	Area

---------			--- 	-------/---------	    ---- 	-------	----

10.2.2.0/255.255.255.0 	0	 0.0.0.0/vlan2 	1	 IntraArea	 0.0.0.2

10.4.0.0/255.255.0.0	 0	 0.0.0.0/vlan1 	1	 IntraArea	 0.0.0.0

90.0.0.0/255.0.0.0 	0	 10.2.2.9/vlan2	 10	 Type2 Ext	0.0.0.2

In ISS4

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask			 TOS 	NextHop/Interface	   Cost 	Rt.Type 	Area

---------			--- 	-------/---------	    ---- 	-------	----

10.2.2.0/255.255.255.0 0 	10.4.0.2/vlan1	 2 InterArea 0.0.0.0	10.4.0.0/255.255.0.0 0	 0.0.0.0/vlan1	 1 IntraArea 0.0.0.0

90.0.0.0/255.0.0.0 0 	10.4.0.2/vlan1	 10 Type2Ext 	0.0.0.0

In ISS4

iS5comm# show ip ospf database nssa-external

OSPF Router with ID (10.2.2.9)

NSSA External Link States (Area 0.0.0.2)

---------------------------------------------

LS age: 300

Options:  (No ToS Capability, DC)

LS Type: NSSA External Link

Link State ID: 90.0.0.0

Advertising Router 	: 10.2.2.9

Advertising Router 	: 10.2.2.9

LS Seq Number	: 0x80000001

Checksum	: 0xc84f

Length	: 36

NSSA External Link States (Area 0.0.0.2)

---------------------------------------------

LS age	: 300

Options	: (No ToS Capability, DC)

LS Type	: NSSA External Link

Link State ID	: 0.0.0.0

Advertising Router 	: 10.4.0.2

LS Seq Number	: 0x80000002

Checksum	: 0x120

Length	: 36

iS5comm# show ip ospf summary-address

Display of Summary addresses for Type5 and Type7 from redistributed routes

OSPF External Summary Address Configuration Information

-----------------------------------------------------

Network		 Mask 		Area 		Effect 	TranslationState

-------		----		----		------	---------------

90.0.0.0 255.0.0.0 0.0.0.2 	advertiseMatching enabled

iS5comm# show ip route

O 0.0.0.0/0		[2] via 10.2.2.2

C 10.2.2.0/24	is directly connected, vlan2

O 10.4.0.0/16 	[2] via 10.2.2.2

90.0.0.0 255.0.0.0 0.0.0.2	 advertiseMatching enabled

C 12.0.0.0/8 is directly connected, vlan1

S	90.1.0.0/16	[1]	via	10.2.2.2

S	90.2.0.0/16	[1]	via	10.2.2.2

S	90.3.0.0/16	[1]	via	10.2.2.2

S	90.4.0.0/16	[1]	via	10.2.2.2

S	90.5.0.0/16	[1]	via	10.2.2.2

iS5comm# show ip ospf route

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask		TOS  NextHop/Interface	Cost	Rt.Type		Area

--------		---	-------/---------	----	-------		----

0.0.0.0/0.0.0.0 0	 10.2.2.2/vlan2	 2	 Type1Ext	 0.0.0.2

10.2.2.0/255.255.255.0 	0	 0.0.0.0/vlan2 	1	 IntraArea 	0.0.0.210.4.0.0/255.255.0.0 0	 10.2.2.2/vlan2 	2 	InterArea	0.0.0.2

Testing of ISS2, ISS4 and ISS9

Note: Test ISS9

Test “no summary- address” command.

Type the following:

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config)# ip route 90.5.0.0	255.255.0.0	10.2.2.2

View the configuration detail in ISS9.

Type the following

iS5comm# show ip ospf summary-address

Display of Summary addresses for Type5 and Type7 from redistributed routes

Observe that nssa-external LSA is generated for all static routes

Type the following

iS5comm# iS5comm# show ip ospf database

OSPF Router with ID (10.2.2.9)

Router Link States (Area 0.0.0.2)

---------------------------------------

Link ID	ADV Router	Age	Seq#	Checksum	Link count

-------	----------	---	----	--------	----------

10.4.0.2 	10.4.0.2 	300	 0x80000006	 0x1dc6	 1

10.2.2.9	10.2.2.9	300	0x80000007	0xec0	1

Network Link States (Area 0.0.0.2)

---------------------------------------

Link ID	ADV Router	Age	Seq#	Checksum

-------	----------	---	----	--------

10.2.2.9	10.2.2.9	300	0x80000002	0x5290

Summary Link States (Area 0.0.0.2)

-------------------------------------

Link ID	ADV Router	Age	Seq#	Checksum

-------	----------	---	----	--------

10.4.0.0	10.4.0.2	300	0x80000003	0x56c5

NSSA External Link States (Area 0.0.0.2)

----------------------------------------

Link ID	ADV Router	Age	Seq#	Checksum

-------	----------	---	----	--------

90.4.0.0 	10.2.2.9 	300	 0x80000001	 0x36e4

90.5.0.0	 10.2.2.9	 300	 0x80000001 	0x2aef

0.0.0.0 	10.4.0.2 	300 	0x80000003 	0xfe21

90.1.0.0 	10.2.2.9 	300	 0x80000001 	0x5ac3

90.2.0.0 	10.2.2.9	 300	 0x80000001 	0x4ece

90.3.0.0	 10.2.2.9	 300	 0x80000001 	0x42d9

Note: Test ISS2

View the OSPF external routes corresponding to all NSSA-external LSAs.

Type the following:

iS5comm# show ip ospf route

OSPF Process Routing Table

Dest/Mask 	TOS	 NextHop/Interface 	Cost	 Rt.Type		 Area

---------	---	-------/---------	----	-------		----

10.2.2.0/255.255.255.0 	0	 0.0.0.0/vlan2	1 IntraArea 0.0.0.2

10.4.0.0/255.255.0.0    0 0.0.0.0/vlan1	1 IntraArea 0.0.0.0

90.1.0.0/255.255.0.0 0	 10.2.2.2/vlan2	10 Type2Ext 0.0.0.2

90.2.0.0/255.255.0.0    0	 10.2.2.2/vlan2	10 Type2Ext 0.0.0.2

90.3.0.0/255.255.0.0    0	 10.2.2.2/vlan2	10 Type2Ext 0.0.0.2

90.4.0.0/255.255.0.0    0	 10.2.2.2/vlan2	10 Type2Ext 0.0.0.2

90.5.0.0/255.255.0.0    0	 10.2.2.2/vlan2	10 Type2Ext 0.0.0.2

Test the area default-cost command.

Type the following:

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# area 0.0.0.2 default-cost 50

Test ISS9

Note:

ISS2 sends a type 7 LSA for the default route with the updated metric as 50. Therefore, the metric for the default route should be 51 in ISS9.

In ISS9, view the configuration.

Type the following:

iS5comm# show ip ospf route

Dest/Mask		 TOS	 NextHop/Interface	  Cost 		Rt.Type 	Area

---------		--	-------/---------	   ----	-------	----

0.0.0.0/0.0.0.0         0	 10.2.2.2/vlan2	 51	 Type1Ext 	0.0.0.2

10.2.2.0/255.255.255.0 	0	 0.0.0.0/vlan2	 1	 IntraArea	 0.0.0.2

10.4.0.0/255.255.0.0 	0	 10.2.2.2/vlan2 2	 InterArea 	0.0.0.2

in ISS2, test the “no area default-cost” command.

Type the following:

iS5comm# configure terminal

iS5comm(config)# router ospf

iS5comm(config-router)# no area 0.0.0.2 default-cost

IN ISS9

Note:

ISS2 must have sent a type 7 LSA for the default route with the updated default metric as 10. Therefore, the metric for the default route must be 11 in ISS9.

In ISS9, view the configuration.

Type the following:

iS5comm# show ip ospf route

Dest/Mask		 TOS	 NextHop/Interface	  Cost 		Rt.Type 	Area

---------		--	-------/---------	   ----	-------	----

0.0.0.0/0.0.0.0         0	 10.2.2.2/vlan2	 11	 Type1Ext 	0.0.0.2

10.2.2.0/255.255.255.0 	0	 0.0.0.0/vlan2	 1	 IntraArea	 0.0.0.2

10.4.0.0/255.255.0.0 	0	 10.2.2.2/vlan2 2	 InterArea 	0.0.0.2

Configuring NSSA asbr-default-route translator

Configuring NSSA asbr-default-route translator enables/disables setting of P bit in the default Type-7 LSA generated by NSSA internal ASBR.

Execute the following commands to configure the NSSA asbr-default-route translator.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

Enable nssa asbr-default-route translator.

iS5comm(config-router)# set nssa asbr-default-route translator enable

Note:

Disable nssa asbr-default-route translator by executing the following command

iS5comm(config-router)# set nssa asbr-default-route translator disable

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring NSSA Area Translation Role

Configuring NSSA Area Translation Role configures the translation role for the NSSA as always or candidate.

Execute the following commands to configure the NSSA asbr-default-route translator.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

Enable nssa asbr-default-route translator.

iS5comm(config-router)# set nssa asbr-default-route translator enable

Note:

Disable nssa asbr-default-route translator by executing the following command

iS5comm(config-router)# set nssa asbr-default-route translator disable

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring Stability Interval for NSSA

This section configures the number of seconds after which an elected translator determines that its services are no longer required, and that it must continue to perform its translation duties for NSSA.

Execute the following commands to configure the stability Interval for NSSA.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the ASBR router status.

iS5comm(config-router)# asbr router

Configure the OSPF interface.

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the area 0.0.0.6 as a NSSA area.

iS5comm(config-router)# area 0.0.0.6 nssa

Configure the stability interval for the NSSA area 0.0.0.6 as 120 seconds.

iS5comm(config-router)# area 0.0.0.6 stability-interval 120

Note:

Go back to the default stability interval for the NSSA area 0.0.0.6 by executing the following command.

iS5comm(config-router)# no area 0.0.0.6 stability-interval

Note:

The default value for stability interval is 40 seconds and is configured using the command no area <area-id> stability-interval.

Exit from the Interface Configuration mode.

iS5comm(config-if)# end

Configuring ABR-Type

Configuring abr-type sets the ABR-Type as either standard, or Cisco, or IBM.

Execute the following commands to configure the abr-type.
Type the following:
- Enter the Global Configuration Mode in ISS1.
```
iS5comm# configure terminal
```
- Enable OSPF globally in the switch ISS1.
```
iS5comm(config)# router ospf
```
- Configure the OSPF router-id
```
iS5comm(config-router)# router-id 10.10.2.1
```
- Configure the OSPF interface.
```
iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0
```
```
iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6
```
- Configure the ABR type as Cisco.
```
iS5comm(config-router)# abr-type cisco
```
Note:
The default value ABR type is standard.
- Exit from the Router Configuration mode.
```
iS5comm(config-router)# end
```

View the configuration details by executing the following show command.

Type the following:

iS5comm# show ip ospf

OSPF Router ID 10.10.2.1

Supports only single TOS(TOS0) route

ABR Type supported is Cisco ABR

It is an Area Border Router

Number of Areas in this router is 2 Area is 0.0.0.6

Number of interfaces in this area is 1

SPF algorithm executed 3 times

Area is 0.0.0.0

Number of interfaces in this area is 1

SPF algorithm executed 3 times

Configuring RFC 1583 Compatibility

Configuring RFC 1583 Compatibility sets the OSPF compatibility list to be compatible with the RFC 1583.

Execute the following commands to configure the RFC 1583 Compatibility.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the RFC1583 compatibility.

iS5comm(config-router)# compatible rfc1583

Note: Disable RFC 1583 compatibility by executing the following command.

iS5comm(config-router)# no compatible rfc1583

Generation of a Default External Route

Configuring Default-information Originate Always enables generation of a default external route into the OSPF routing domain and other parameters related to that area.

Execute the following commands to configure the Default-information Originate Always.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the ASBR router status.

iS5comm(config-router)# asbr router

Configure the generation of a default external route.

iS5comm(config-router)# default-information originate always metric 40

Note:

Disable generation of a default external route by executing the following command.

iS5comm(config-router)# no default-information originate always

Note:

Refer to Figure Topology for Testing Generation of a Default External Route and Redistribution Configuration.

Configuring Redistribution Configuration

Configuring redistribution configuration configures the information to be applied to routes learnt from RTM.

Execute the following commands to configure Redistribution.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the ASBR router.

iS5comm(config-router)# asbr router

Configure the redistribution of static routes.

iS5comm(config-router)# redistribute static

Configure the redistribution configuration.

iS5comm(config-router)# redist-config 20.0.0.0 255.0.0.0 metric-value 100 metric-type asExttype1 tag 10

Note:

Delete the information applied to the routes learnt from RTM by executing the following command

iS5comm(config-router)# no redist-config 20.0.0.0 255.0.0.0

Figure 3. Topology for Testing Generation of a Default External Route and Redistribution

Sample Configuration for testing default-information originate always and redist-config.

Some prerequisite configuration (refer to Section Configuration Guidelines (Prerequisite)) must be done in the switches ISS1 & ISS2 before configuring OSPF.

Configuration of ISS1

Execute the following commands in ISS1 to configure the generation of a default external route.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the ASBR router.

iS5comm(config-router)# asbr router

Configure the generation of a default external route.

iS5comm(config-router)# default-information originate always metric 40

Exit from the Router Configuration mode.

iS5comm(config-router)# end

Configuration of ISS2

Execute the following commands in ISS2.

Type the following:

Enter the Global Configuration Mode in ISS2.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS2

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.4.0.2

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.2 area 0.0.0.0

iS5comm(config-router)# network 10.2.2.2 area 0.0.0.2

Configure area 0.0.0.2 as an NSSA area.

iS5comm(config-router)# area 0.0.0.2 nssa

Exit from the Router Configuration mode.

iS5comm(config-router)# end

View the configuration details by executing the following show command in ISS1.

Type the following:

iS5comm# show ip ospf database external

OSPF Router with ID (10.10.2.1)

AS External Link States

-----------------------

LS age	: 0

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID: 0.0.0.0

Advertising Router : 10.10.2.1

LS Seq Number	: 0x80000001

Checksum	: 0xb5dd

Length	: 36

Network Mask	: 0.0.0.0

Metric Type	: 0x80

Metric	: 40

Forward Address	: 0.0.0.0

Externel Route Tag	: 0

View the configuration details by executing the following show command in ISS2.

Type the following:

iS5comm# show ip ospf route

OSPF Process Routing Table

 	Dest/Mask	  TOS	NextHop/Interface		Cost	Rt.Type		Area

---------	  ---	-------/---------		----	-------		----

0.0.0.0/0.0.0.0   0	 10.4.0.1/vlan1	 40 Type2Ext 	0.0.0.0

10.2.2.0/255.255.255.0 0	 0.0.0.0/vlan2	       1 IntraArea       0.0.0.2

10.4.0.0/255.255.0.0   0 	0.0.0.0/vlan1	       1 IntraArea       0.0.0.0

10.10.0.0/255.255.0.0  0	 10.4.0.1/vlan1	       2 InterArea      0.0.0.0

Execute the following commands in ISS1 to configure the generation of a default external route.
Type the following:
- Enter the Global Configuration Mode in ISS1.
```
iS5comm# configure terminal
```
- Enable OSPF globally in the switch ISS1.
```
iS5comm(config)# router ospf
```
- Configure the default external route.
```
iS5comm(config-router)# no default-information originate always
```
- Exit from the Router Configuration mode.
```
iS5comm(config-router)# end
```
View the configuration details by executing the following show command in ISS1. Type 5 External LSA for the default route must be flushed
Type the following:
```
iS5comm# show ip ospf database external
```
```
OSPF Router with ID (10.10.2.1)
```

View the configuration details by executing the following show command in ISS2. The route entry for the default route must be deleted.

Type the following:

iS5comm# show ip ospf route

OSPF Process Routing Table

 	Dest/Mask	  TOS	NextHop/Interface		Cost	Rt.Type		Area

---------	  ---	-------/---------		----	-------		----

10.2.2.0/255.255.255.0 0	 0.0.0.0/vlan2	       1 IntraArea       0.0.0.2

10.4.0.0/255.255.0.0   0	 0.0.0.0/vlan1	       1 IntraArea       0.0.0.0

10.10.0.0/255.255.0.0  0	 10.4.0.1/vlan1	       2 InterArea      0.0.0.0

Execute the following commands in ISS1 to configure the generation of a default external route.
Type the following:
- Enter the Global Configuration Mode in ISS1.
```
iS5comm# configure terminal
```
- Enable OSPF globally in the switch ISS1.
```
iS5comm(config)# router ospf
```
- Configure the default external route.
```
iS5comm(config-router)# no default-information originate always
```
- Exit from the Router Configuration mode.
```
iS5comm(config-router)# end
```
View the configuration details by executing the following show command in ISS1. Type 5 External LSA for the default route must be flushed
Type the following:
```
iS5comm# show ip ospf database external
```
```
OSPF Router with ID (10.10.2.1)
```

View the configuration details by executing the following show command in ISS2. The route entry for the default route must be deleted.

Type the following:

iS5comm# show ip ospf route

OSPF Process Routing Table

 	Dest/Mask	  TOS	NextHop/Interface		Cost	Rt.Type		Area

---------	  ---	-------/---------		----	-------		----

10.2.2.0/255.255.255.0 0	 0.0.0.0/vlan2	       1 IntraArea       0.0.0.2

10.4.0.0/255.255.0.0   0	 0.0.0.0/vlan1	       1 IntraArea       0.0.0.0

10.10.0.0/255.255.0.0  0	 10.4.0.1/vlan1	       2 InterArea      0.0.0.0

Configuration in ISS1

Execute the following commands in ISS1 to test redist-config.
Type the following:
- Enter the Global Configuration Mode in ISS1.
```
iS5comm# configure terminal
```
- Enable OSPF globally in the switch ISS1.
```
iS5comm(config)# router ospf
```
- Configure redistribution of static routes redist-config.
```
iS5comm(config-router)# redistribute static
```
- Configure redist-config.
```
iS5comm(config-router)# redist-config 20.0.0.0 255.0.0.0 metric-value 100 metric-type asExttype1 tag 10
```
```
iS5comm(config-router)# exit
```
- Add a static route for 20.0.0.0/8 network.
iS5comm(config)# ip route 20.0.0.0 255.0.0.0 10.4.0.2
- Exit from the Global Configuration mode.
```
iS5comm(config)# exit
```

View the configuration details by executing the following show command in ISS1. An external LSA is generated for 20.0.0.0 with metric as 100, metric type as asExtType1, and tag 10.

Type the following:

iS5comm# show ip ospf database external

OSPF Router with ID (10.10.2.1)

AS External Link States

-----------------------

LS age	: 600

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 20.0.0.0

Advertising Router 	: 10.10.2.1

LS Seq Number	: 0x80000001

Checksum	: 0xf6b2

Length	: 36

Network Mask	: 255.0.0.0

Metric Type	: 0x0

Metric	: 100

Forward Address	: 10.4.0.2

In ISS2:

View the external route 20.0.0.0/8 with metric as 101.

Type the following:

iS5comm# show ip ospf route

OSPF Process Routing Table

 	Dest/Mask	  TOS	NextHop/Interface		Cost	Rt.Type		Area

---------	  ---	-------/---------		----	-------		----

10.4.0.0/255.255.255.0 0	 0.0.0.0/vlan1 1 IntraArea       0.0.0.0

10.10.0.0/255.255.0.0   0	 0.0.0.0/vlan1	       2 IntraArea       0.0.0.0

20.0.0.0/255.0.0.0  0	 10.4.0.2/vlan1	       101 Type1Ext 0.0.0.0

10.2.2.0/255.255.255.0 0	 0.0.0.0/vlan2	       1 IntraArea       0.0.0.2

Configuration in ISS2

Execute the following commands in ISS1 to test no redist-config.
Type the following:
- Enter the Global Configuration Mode in ISS1.
```
iS5comm# configure terminal
```
- Enable OSPF globally in the switch ISS1.
```
iS5comm(config)# router ospf
```
- Configure no redist-config.
```
iS5comm(config-router)# no redist-config 20.0.0.0 255.0.0.0
```
- Exit from the Router Configuration mode.
```
iS5comm(config-router)# exit
```

View the configuration details by executing the following show command. The external LSA generated for 20.0.0.0 with metric as 100, metric type as asExtType1, and tag as 10 is flushed and a new external LSA is generated with the default redistribution configuration.

Type the following:

iS5comm# show ip ospf database external

OSPF Router with ID (10.10.2.1)

AS External Link States

-----------------------

LS age	: 0

Options	: (No ToS Capability, DC)

LS Type	: AS External Link

Link State ID	: 20.0.0.0

Advertising Router 	: 10.10.2.1

LS Seq Number	: 0x80000002

Checksum	: 0x3c5

Length	: 36

Network Mask	: 255.0.0.0

Metric Type	: 0x0

Metric	: 10

Forward Address	: 10.4.0.2

Externel Route Tag: 0

Configuring Neighbor

Configuring Neighbor specifies an NBMA (Non Broadcast Multi Access) neighbor router and its priority.

Execute the following commands to configure a Neighbor.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Exit from the Router Configuration mode.

iS5comm(config-router)# end

Enter the Interface Configuration mode.

iS5comm(config-if)# interface vlan 1

Configure the network type as NBMA.

iS5comm(config-if)# ip ospf network non-broadcast

Configure the neighbor with priority.

iS5comm(config-if)# exit

iS5comm(config)# router ospf

iS5comm(config-router)# neighbor 10.4.0.2 priority 10

Configure the neighbor with default priority.

iS5comm(config-if)# no neighbor 10.4.0.2 priority 10

Note:

Delete the configured neighbor by executing the following command.

iS5comm(config-router)# no neighbor 10.4.0.2

Configuring Virtual Link

Configuring Virtual Link defines an OSPF virtual link and its related parameters.

Execute the following commands to configure the Virtual Link.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the virtual link.

iS5comm(config-router)# area 0.0.0.6 virtual-link 20.0.0.1 authentication message-digest hello-interval 100 retransmit-interval 100 transmit-delay 50 dead-interval 200 authentication-key asdf

Note: Delete the virtual link by executing the following command.

iS5comm(config-router)# no area 0.0.0.6 virtual-link 20.0.0.1

Note: Refer to Sample Configuration for testing virtual link and route summarization

Configuring Virtual Link with SHA-1

Configuring Virtual Link defines an OSPF virtual link and its related parameters.

Execute the following commands to configure the Virtual Link.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the virtual link with sha-1. Here, the sha-1 can be replaced by the sha-2 algorithms such as sha-224/ sha-256/ sha-384/ sha-512.

iS5comm(config-router)# area 0.0.0.6 virtual-link 20.0.0.1 authentication sha-1 hello-interval 100 retransmit-interval 100 transmit-delay 50 dead-interval 200 message-digest-key 1 sha-1 abcd

Note: Delete the virtual link by executing the following command.

iS5comm(config-router)# no area 0.0.0.6 virtual-link 20.0.0.1

Note: Refer to Sample Configuration for testing virtual link and route summarization

Configuring Area-range

The area-range is configured to consolidate and summarize routes at an area boundary.

Execute the following commands to configure the route summarization at an area border router.

Type the following:

Enter the Global Configuration Mode in ISS1.

iS5comm# configure terminal

Enable OSPF globally in the switch ISS1.

iS5comm(config)# router ospf

Configure the OSPF router-id.

iS5comm(config-router)# router-id 10.10.2.1

Configure the OSPF interface.

iS5comm(config-router)# network 10.4.0.1 area 0.0.0.0

iS5comm(config-router)# network 10.10.2.1 area 0.0.0.6

Configure the route summarization at an area border router.

iS5comm(config-router)# area 0.0.0.6 range 10.10.0.0 255.255.0.0 summary

Note: Delete the route summarization information by executing the following command.

iS5comm(config-router)# no area 0.0.0.6 range 10.10.0.0 255.255.0.0