Solved: Virtual Link issues

DanDan · ‎02-03-2022

Hi all!

I came across issue when configuring OSPFv3 and trying to set up a virtual link. Under regular OSPF, under ospf subconfiguration, I use # area ( # of transit area ) virtual-link and Router-ID of a neighbor. With OSPFv3 I got little lost.

The commands is not an option, even under the address family subconfiguration. After research I found there is a need to configure following : #ipv6 router ospf (instance number), and then area ( # of transit area ) virtual-link and Router-ID of a neighbor, the virtual link doesnt come up and I cant find an answer.

I am attaching config from R2 and R4, thank you in advance for taking time to have a look on my issue. Not sure what am I doing wrong.

R2(config)# do sh run
Building configuration...

Current configuration : 3308 bytes
!
! Last configuration change at 20:52:26 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
interface GigabitEthernet0/1
ip address 31.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::1/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 51.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 51::1/64
ospfv3 100 ipv6 area 30
ospfv3 100 ipv4 area 30
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 2.2.2.2
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ipv6 router ospf 1
area 20 virtual-link 4.4.4.4










R4#show run
Building configuration...

Current configuration : 3391 bytes
!
! Last configuration change at 21:02:01 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
ip address 41.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 42::2/64
ospfv3 100 ipv6 area 10
ospfv3 100 ipv4 area 10
!
interface GigabitEthernet0/1
ip address 31.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::2/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 21.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 21::1/64
ospfv3 100 ipv6 area 0
ospfv3 100 ipv4 area 0
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 4.4.4.4
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server
!
ipv6 router ospf 1
area 20 virtual-link 2.2.2.2

Georg Pauwen · ‎02-03-2022

Hello,

I don't think configuring the VL under the IPv6 address family works at all. It needs to be configured under the IPv4 address family.

View solution in original post

Georg Pauwen · ‎02-04-2022

Hello,

I recreated your setup in a lab and added the virtual links under the IPv6 address family of ospfv3 100. That might be the problem: you are creating a new process (1) which is not configured anywhere.

With the below config (addition marked in bold) the VL came up right away:

R2(config)# do sh run
Building configuration...

Current configuration : 3308 bytes
!
! Last configuration change at 20:52:26 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
interface GigabitEthernet0/1
ip address 31.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::1/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 51.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 51::1/64
ospfv3 100 ipv6 area 30
ospfv3 100 ipv4 area 30
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 2.2.2.2
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
--> area 20 virtual-link 4.4.4.4
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server










R4#show run
Building configuration...

Current configuration : 3391 bytes
!
! Last configuration change at 21:02:01 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
ip address 41.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 42::2/64
ospfv3 100 ipv6 area 10
ospfv3 100 ipv4 area 10
!
interface GigabitEthernet0/1
ip address 31.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::2/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 21.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 21::1/64
ospfv3 100 ipv6 area 0
ospfv3 100 ipv4 area 0
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 4.4.4.4
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
--> area 20 virtual-link 2.2.2.2
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server

View solution in original post

DanDan · ‎02-04-2022

Georg,

It wont work with OSPFv3 the ipv4. Found it.

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.

Thank you for your help.

Daniel.

View solution in original post

Georg Pauwen · ‎02-03-2022

Hello,

I don't think configuring the VL under the IPv6 address family works at all. It needs to be configured under the IPv4 address family.

DanDan · ‎02-03-2022

Hi Georg,

I have tried to do that but that does not work as well.

Georg Pauwen · ‎02-04-2022

Hello,

I recreated your setup in a lab and added the virtual links under the IPv6 address family of ospfv3 100. That might be the problem: you are creating a new process (1) which is not configured anywhere.

With the below config (addition marked in bold) the VL came up right away:

R2(config)# do sh run
Building configuration...

Current configuration : 3308 bytes
!
! Last configuration change at 20:52:26 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
interface GigabitEthernet0/1
ip address 31.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::1/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 51.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 51::1/64
ospfv3 100 ipv6 area 30
ospfv3 100 ipv4 area 30
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 2.2.2.2
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
--> area 20 virtual-link 4.4.4.4
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server










R4#show run
Building configuration...

Current configuration : 3391 bytes
!
! Last configuration change at 21:02:01 UTC Thu Feb 3 2022
!
version 15.9
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R4
!
boot-start-marker
boot-end-marker
!
no aaa new-model
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
!
ip cef
ipv6 unicast-routing
ipv6 cef
!
multilink bundle-name authenticated
!
redundancy
!
interface GigabitEthernet0/0
ip address 41.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 42::2/64
ospfv3 100 ipv6 area 10
ospfv3 100 ipv4 area 10
!
interface GigabitEthernet0/1
ip address 31.0.0.2 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 31::2/64
ospfv3 100 ipv6 area 20
ospfv3 100 ipv4 area 20
!
interface GigabitEthernet0/2
ip address 21.0.0.1 255.255.255.252
duplex auto
speed auto
media-type rj45
ipv6 address 21::1/64
ospfv3 100 ipv6 area 0
ospfv3 100 ipv4 area 0
!
interface GigabitEthernet0/3
no ip address
shutdown
duplex auto
speed auto
media-type rj45
!
router ospfv3 100
router-id 4.4.4.4
!
address-family ipv4 unicast
exit-address-family
!
address-family ipv6 unicast
--> area 20 virtual-link 2.2.2.2
exit-address-family
!
ip forward-protocol nd
!
no ip http server
no ip http secure-server

DanDan · ‎02-04-2022

Hi Georg,

Once again thank you for your help.

That works absolutely fine. However ipv4 does not work and have tried under the address family, outside of address family, tried multiple things but no luck. Are we only able to create virtual link for ipv6? I did some research but so far no luck to find the solution, or just an explanation.

Daniel.

DanDan · ‎02-04-2022

Georg,

It wont work with OSPFv3 the ipv4. Found it.

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.

Thank you for your help.

Daniel.

Georg Pauwen · ‎02-04-2022

Hello,

good find ! Thanks for sharing, that is useful information !