IPv6 unnumbered in Cisco Modeling Lab with Nexus 9300 9.3.6

[christianpho]

Hi,

I'm trying to setting up a leaf and spine archictecture not using ACI or any other SDN system for lab purpose.

I like to use IPv6 as underlay routed protocol.

In the documentation I look the author did not used IPv6 in his documentation.  He propose to use unnumbered interface to established OSPF relationship between switches and barrow the IP address of LO0 of each unit to established OSPF relationship.

I'm currently using Cisco Modeling Lab for this lab.   

All devices in the topology are Nexus 9300V running 9.3.6

under interface configuration I define the medium as p2p

interface Ethernet1/1
  medium p2p
  vrf member UNDERLAY
  ip unnumbered loopback0
  ipv6 router ospfv3 UNDERLAY area 0.0.0.0
  no shutdown

I have the possibility to define IPv4 unnumbered (like already configured) but not IPv6 

SPINE-2(config-if)# ipv6 ?
  address         Configure IPv6 address on interface
  dhcp            Configure IPv6 DHCP on L2 interface
  icmp            ICMPv6 commands
  link-local      Change format of link-local address
  mld             MLD interface configuration commands
  nd              Configure IPv6 ND
  nd              ICMPv6 Neighbor Discovery commands
  neighbor        Configure IPv6 address to layer-2 address mapping
  port            Port policy
  redirects       Enable sending ICMPv6 Redirect messages
  router          Enable a routing process
  snooping        IPv6 snooping configuration commands
  traffic-filter  Specify access control for packets
  unreachables    Enable sending ICMPv6 Unreachable messages (port-unreachables
                  are always rate-limit enabled) 
  verify          Unicast Reverse Path Forwarding

What I missed in the configuration ?

If I use link local address my OSPFv3 neighborship works fine, but I'm getting bigger IPv6 routing table....  the link local addresses are appering in it as local network. 

I also find that their is no option for IPv4 address family under the OSPFv3 process....  does it mean that I will need to enable both routing protocol since I will be need to route both at the for customer traffic IPv4 and IPv6 ?

SPINE-2(config-router)# address-family ?
  ipv6  Configure IPv6 address-family

SPINE-2(config-router)# exit
SPINE-2(config)# feat
feature       feature-set   
SPINE-2(config)# feature osp
ospf     ospfv3   
SPINE-2(config)# feature ospf
SPINE-2(config)# router ospfv3 UNDERLAY
SPINE-2(config-router)# address-family ?
  ipv6  Configure IPv6 address-family

even after enabling ospfv2 as feature the IPV4 address family is still not listed.

I haven't looked yet, but if both address family area aren't available with OSPF is this reality will be the same with all other routing protocol like MP-BGP, EIGRP and ISIS ?

[Harold Ritter · Accepted solution]

Hi @christianpho ,

It looks like the "ipv6 unnumbered" is not yet supported on the Nexus 9000. If the goal is not to assign IPv6 addresses to the spines and leaves, you could just use link local addresses (LLA) on the transit links. This way, ospfv3 will be able to establish the neighbor relationship without having to assign global unicast address (GUA) on the transit links, which more or less gives you the functionality of "ipv6 unnumbered".

interface Ethernet1/1
ipv6 address use-link-local-only
ipv6 router ospfv3 UNDERLAY area 0.0.0.0

It does not look like ospfv3 supports "address-family ipv4" on the Nexus 9k either yet. Not sure if or when it is planned. You will need to continue to run ospfv2 and ospfv3.

ISIS, EIGRP and BGP support both "address-family ipv4" and "address-family ipv6"

Regards,