IPv6 DMVPN

• DMVPN uses IPv4 mGRE for transport.
  • GRE is a multiprotocol encap.
  • Implies IPv6 can be supported.
• How IPv6 over IPv4 DMVPN works.
  • Build IPv4 underlay and overlay.
    • IPSEC spoke to hub.
  • Use IPv6 NHRP to resolve IPv6 IGP or IPv6 BGP.

The topology above is running DMVPN Phase 3 with EIGRP. R5 is the Hub and R1-3 are the spokes.

The below configurations will add IPv6 over the DMVPN configurations.

Hub:

Spoke 1:

Notes:

• The hub basically gets an IPv6 address assigned to its tunnel interface, along with the standard NHRP commands. ‘ipv6 nhrp redirect’ is what enables phase 3 on the hub.
• The spoke needs to get an IPv6 address assigned to its tunnel interface, standard NHRP commands as well. In addition, it needs to map the NHS to the IPv6 address of the hub, as well as mapping the NBMA to the hub’s actual physical transport address assigned to Gig0/0.

• A ‘show dmvpn’ on the hub displays the DMVPN spokes as well as our IPv6 addresses that are getting tunneled over mGRE. The configuration is IPv6 over IPv4 DMVPN, but we could have used IPv6 as the underlay/transport as well.