Enable IPv6 for l3_interfaces

[p-rintz]

Enhancement summary

I would like to be able to add IPv6 Addresses to Interfaces.

Which component of AVD is impacted

eos_designs

Use case example

I need to be able to set an IPv6 Address on an uplink interface for BGP connectivity.

Describe the solution you would like

Addition of ipv6_addresses to l3_interfaces.

Describe alternatives you have considered

Currently, setting the IPv6 via custom structured configs or raw_eos_cli is the only alternative.

Additional context

No response

Contributing Guide

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[theotherguy2175]

I would also love to have this feature. We can't use l3_interfaces because of it.

[theotherguy2175]

Not sure why they have not responded but was able to do a work around:

 - interfaces: [ Ethernet1/1 ]
             nodes: [ borderA ]
             description: L3PEER-I
             mtu: 9174
             enabled: false
             ip_addresses: [ 1.1.1.1/30 ]
             # ospf:
             #   enabled: true
             #   point_to_point: True
             structured_config:
               ipv6_address: 2001::1/64
               speed: forced 40gfull
               access_group_in: SANITY-IN

The structured config here is very handy for any 'ethernet' eos cli

[steve-hartt]

Not sure why they have not responded but was able to do a work around:

 - interfaces: [ Ethernet1/1 ]
             nodes: [ borderA ]
             description: L3PEER-I
             mtu: 9174
             enabled: false
             ip_addresses: [ 1.1.1.1/30 ]
             # ospf:
             #   enabled: true
             #   point_to_point: True
             structured_config:
               ipv6_address: 2001::1/64
               speed: forced 40gfull
               access_group_in: SANITY-IN

The structured config here is very handy for any 'ethernet' eos cli

can the structured config be done if there are multiple devices in 'nodes'?