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Virtual Link for IPv4 Address Family in OSPFv3

Tim K
Level 1
Level 1

I was wondering if there is any support for virtual links in the IPv4 address family of OSPFv3. Has anyone seen it? I saw one article on Cisco's website that it isn't supported, but maybe it's an old article? Has anyone been able to make VL's work in this scenario?

 

http://www.cisco.com/en/US/docs/ios-xml/ios/ipv6/configuration/15-0sy/ip6-ospf.html

- Look at the Note under the OSPFv3 Virtual Links

 

Also, see below output. There is no option for virtual links!

 

PE1(config)#router ospfv3 1
PE1(config-router)#address-family ipv4

PE1(config-router-af)#area 1 ?
  authentication  Enable authentication
  default-cost    Set the summary default-cost of a NSSA/stub area
  filter-list     Filter networks between OSPFv3 areas
  normal          Specify a normal area type
  nssa            Specify a NSSA area
  range           Summarize routes matching address/mask (border routers only)
  stub            Specify a stub area
  transit         Use this router to transit data

 

 

 

3 Replies 3

Peter Paluch
Cisco Employee
Cisco Employee

Hi Tim,

Checked on my VIRL IOSv 15.5(3)M, no luck - the virtual link does not seem to be supported for IPv4 AF.

I am thinking whether there is some technical limitation that would actually prevent this virtual link from being established, or whether it is just a rarely-used feature for OSPFv3+IPv4 AF so Cisco didn't implement it. No firm ideas on this as of yet - I'll keep you posted if I have more details.

Best regards,
Peter

Moh Mogh
Level 1
Level 1

Hi Tim,

RFC5838 says:

   OSPFv3 control packets sent over a virtual link are IPv6 packets and
   may traverse multiple hops.  Therefore, there MUST be a global IPv6
   address associated with the virtual link so that OSPFv3 control
   packets are forwarded correctly by the intermediate hops between
   virtual link endpoints.  Although this requirement can be satisfied
   in IPv6 unicast AFs, it will not function in other AFs as there will
   not be a routable global IPv6 address or forwarding path.  Therefore,
   virtual links are not supported in AFs other than IPv6 unicast.

 

So, it explains why it's not supported.

Thanks,
Mohammad

Thanks for the response. I was hoping that maybe creating an IPv6 VL would allow the IPv4 routes to be learned. But I tried earlier to create a virtual link on the IPv6 side, which I did successfully. However, that did not help my problem. I still could not learn the route from the area not connected to area 0. Thanks again.

 

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