Configure and Verify OSPF for IPv6

Exam: Cisco 300-101 - Implementing Cisco IP Routing (ROUTE v2.0)

OSPF (Open Shortest Path First) is a link state routing protocol that makes routing decisions on the basis of state of link that connects the source and destination machines. Link state is a description of the interface and its relationship with its neighboring network devices. It describes an interface has with information such as the type of network it is connected to, the network mask, the router connected to the network, the IPv6 prefix of the interface, and so on. This information is advertised in different types of LSAs (link state advertisements).

To support IPv6, OSPF introduced a newer version known as OSPF version 3 (OSPFv3). In this version, the fundamental mechanism and the algorithm is same as OSPFv2, but due to 128 bit in IPv6 addresses, the packet and LSA formats are different. The IPv6 OSPF uses address family feature to enable the IPv6 unicast traffic support.

The command address family is used to determine the type of address family run in OSPF process. You can configure only one address family per instance. The configuration of OSPF for IPv6 is performed by enabling Ipv6 unicast routing and enabling IPv6 on an interface.

Configuration of OSPF for IPv6:

The steps to configure OSPF for IPv6 are mentioned below:

Enable the privilege mode

RouterR1 > enable

Enter the global configuration mode

RouterR1 # config t

Configure the router with process id and enable OSPF configuration mode for IPv6 address. Number 4 represents the process id.

RouterR1 (config) # ipv6 router ospf 4

Enable the IPv6 unicast routing on router using command address-family.

RouterR1 (config–router) # address-family ipv6 unicast

Configure the router with an IPv6 address range using area command. The address 3011:AD9:BD1:0::0/128 is used as IPv6 address range.

RouterR1 (config–router-af) # area 4 range 3011:AD9:BD1:0::0/128

Configure the router with default command to return an OSPF parameter to its default value. Number 4 represents the area id.

RouterR1 (config–router-af) # default area 4

Configure the router with default route using default information originate command to generate a default external route into an OSPF for a routing domain. Number 150 represents the metric value and number 3 represents matric type.

RouterR1 (config–router-af) # default-information originate always metric 150 metric-type 3

Configure the router with default value using default metric command for IPv6 routes redistributed into the OSPF routing protocol. Number 20 is used as metric value.

RouterR1 (config–router-af) # default-metric 20

Configure the router with administrative distance using distance command so that OSPF routes inserted into routing table. Number 200 represents the administrative distance.

RouterR1 (config–router-af) # distance 200

Apply the prefix list to routing updates that are sent or received on an interface. Cisco represents the name of prefix list used and Ethernet 0/1 represents the interface on with prefix list is applied.

RouterR1 (config–router-af) # distribute-list prefix-list cisco in Ethernet 0/1

Configure the router with maximum paths command to control the maximum number of equal cost routes that a process for OSPF routing can support. Number 4 represents the number of paths.

RouterR1 (config–router-af) # maximum-paths 4

Configure the router with IPv6 summary prefix. Address DFE0::/24 is used as IPv6 address.

RouterR1 (config–router-af) # summary-prefix DFE0::/24

Exit the address family configuration mode and return to privileged EXEC mode

RouterR1 (config–router-AF) # end

Enabling IPv6 OSPF on an interface

The next step is to enable IPv6 on the router’s interface. The configuration steps required to enable IPv6 on an interface are mentioned below.

Enable the privilege mode

RouterR1 > enable

Enter the global configuration mode

RouterR1# config t

Enter the router’s interface configuration mode and specify the interface type and number of the router. Ethernet 0/1 represents the type of interface and number of router.

RouterR1 (config–router) # interface Ethernet 0/1

Enable the IPv6 on an interface. Number 2 represents OSPF process id and 3 represents area id.

RouterR1 (config–if) # ipv6 ospf 2 area 3

Exit the configuration mode and return to privileged EXEC mode

RouterR1 (config–if) # end

Verification of OSPF for IPv6

After configuring OSPF for IPv6, you may face different kinds of problems related to connectivity such as area id mismatch, packet mismatch or other error messages. For that you need to verify the area id is configured correctly, OSPF neighbor is listed in neighboring table, and the routes are learnt by neighbor.

Use following commands to verify the configuration of OSPF for IPv6:

Displays general information about IPv6 OSPF routing process

RouterR1# Show ipv6 ospf

Displays IPv6 OSPF related interface information

RouterR1# Show ipv6 ospf interface

Displays the link state database (LSDB) of the router

RouterR1# Show ipv6 ospf database

Displays detailed information about IPv6 OSPF events

RouterR1# Show ipv6 ospf event spf

Displays the internal IPv6 OSPF routing table entries to an ABR and ASBR

RouterR1# Show ipv6 ospf border-routers

Displays detailed information about IPv6 OSPF

RouterR1# Show ipv6 ospf events

Displays IPv6 OSPF neighbor information on a per interface basis

RouterR1# Show ipv6 ospf neighbor

Displays IPv6 OSPF routes

RouterR1# Show ipv6 ospf route

Displays list of IPv6 OSPF LSAs waiting to be flooded over an interface

RouterR1# Show ipv6 ospf flood-list

Displays list of all LSAs requested by the router

RouterR1# Show ipv6 ospf request-list

Displays IPv6 OSPF Shortest path first calculation statistics

RouterR1# Show ipv6 ospf statistics

Displays IPv6 OSPF router id and reference bandwidth

RouterR1# Show ipv6 ospf process id

Displays IPv6 OSPF traffic statistics

RouterR1# Show ipv6 ospf traffic

Exam Question:

You are assigned a task of setting up OSPF on an existing router using IPv6. Which of the following commands would you use to enable OSPF for IPv6 on a router?

  1. Router ospf process id
  2. Ipv6 router ospf process id
  3. Ipv6 ospf process id area id
  4. Router ospf process id
  5. None of the above

Answer: 2

Explanation: The command “ipv6 router ospf process id“ is used to enable an OSPF process on the router. It is used in global configuration mode. For example

Router R1 (config) # ipv6 router ospf 1

Where, number 1 represents the process id.

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