Thursday, December 26, 2013

ipv4 ospf routing with OSPFv3

IPv6 ospf routing uses  a new process type known as  ospfv3. Their's a few differences between OSPFv2 and OSPFv3.

Primarily OSPFv2  has suppored ipv4  unicast,  and with MOSPF , we can also support ipv4 multicast routing.

With  OSPFv3,  we can also support both  ipv4+ipv6  unicast and multicast routing within these two common AFI.

I will demonstrate how you can accomplish ipv4 routing on a pair of cisco devices, using  OSPFv3.

Here's out topology;

The 6509 is configured for VRF so we have a simple vrf definition;

NOTE: We have two AFI defined but in reality I  only need  ipv4 unicast for this demo and just for  ipv4 unicast routing.

On the ASR we 1st define our  ospf -process #333 for ipv4  unicasting routing;

Very simple, we define a ospfv3 router instance with a unique process #. We must have one ipv4 address active for the RID. I made our process number match, but they do NOT have to match for ospf routing.

Next, we define our interfaces for the OSPFv3 process. This helps to eliminate the  BDR/DR selection process,  and speed up convergence.  I've built these point-2-point  interface as defined as p2p , in order to take advantage of this. In a multi-access lan, you obviously could not do this. So if you have more than 2 ospf routers on a common segment, then the ospf network-type will be of a broadcast type.

You may notice that I adjust the hello-interval to maxiumum value of 65535. This is a trick to reduce the number of hello that are process on a loopback interface. If you think about it, a hello interval of 10sec ( the default btw ) is useless on a interface that will never built adjacenies to another ospf router.

Okay so far this concludes the  ASR side of things.

The 6509 is configured almost identical, but we a  vrf definition due to we are in a VRF.

Okay now let's check out some of the ospfv3 show commands;


ospfv3 database

interface and neighbors

And now for a full interface show output;

1st the port-channel sub-interface;

notice I highlighted the ipv6 local EUI address. Yes you need ipv6 enable on the interface.

Now the  loopback interface  ;

notice I highlighted the ipv6 local EUI address. Yes you need ipv6 enable on the interface, & also the EUI address  has been computed for a loopback interface. Also we can see the hello/dead timers

A few Key points to keep in mind;

  • OSPFv3 supports multiple  AFI  ( ipv4 unicast/multicast ipv6 unicast/multicast )
  • No need to run a OSPFv2 process for ipv4 routing,  and a OSPFv3 process for ipv6 routing
  • you can collaspe both AFI into one single OSPFv3 process
  • It uses a ip6 link-local address for the ospf adjacenies
  • you have to enable ipv6 under the interface
  • OSPFv3 process #s are built globally
  • You config the ospf process  under the  interfaces
  • you must have ipv6 unicast-routing enabled globally , and regardless if you actually plan on routing ipv6 unicast prefixes
  • the same show commands for  classic OSPFv2 are support in OSPFv3
  • the ospfv3 database are similar but a few new LSA and changes are added with OSPFv3 routing
  • most advance routers support this ( cisco IOS, IOS-XR, Juniper, Brocade )
  • Juniper SRX firewall support multiple AFI , but cisco ASA, Fortinet and Checkpoints does not

Ken Felix
Freelance Network / Security Engineer
kfelix  ----a---t---socpuppets ---d---o---t---com

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