Feat(eos_designs): Single-Active EVPN Multihoming

[jonxstill]

Change Summary

Support single-active EVPN Multihoming.

Related Issue(s)

Fixes #1771

Component(s) name

arista.avd.eos_designs

Proposed changes

This PR introduces a new data model for ESIs in AVD which affects port-channel and ethernet interfaces. Subinterfaces of port-channels are unaffected.

< connected_endpoints_keys.key >:
  < endpoint_1 >:
    adapters:
        # Settings for all- or single-active EVPN multihoming
      - ethernet_segment:

          # Define a manual short-esi (be careful using this on profiles) or auto-generate an ESI | required
          short_esi: < 0000:0000:0000 | auto >

          # Configure this Ethernet Segment for all-active or single-active forwarding | optional
          # If omitted, Port-Channels use the EOS default of all-active
          # If omitted, Ethernet interfaces are explicitly configured as single-active
          redundancy: < all-active | single-active >

          # Configure DF algorithm and preferences | optional
          #  - auto: Use preference-based algorithm and assign preference based on position of 
          #          the device in the 'switches' list
          #          e.g. assuming a list of three switches, this would assign a preference of
          #          200 to the first switch, 100 to the 2nd and 0 to the third
          #  - preference: Set preference for each switch manually using designated_forwarder_preferences key
          #  - modulus: Use the default modulus-based algorithm
          #  - Alternatively a list of preferences can be provided - [500, 250] for example which will be
          #    mapped according the 'switches' list
          # If omitted, Port-Channels use the EOS default of modulus
          # If omitted, Ethernet interfaces default to the 'auto' mechanism detailed above
          designated_forwarder_algorithm: < "auto" | "modulus" | "preference" >
          # manual preference as described above | required only for preference algorithm
          designated_forwarder_preferences: [ < df_preference_for_each_switch > ]
          # Disable preemption for single-active forwarding when auto/manual DF preference is configured | optional
          dont_preempt: < true | false >

If a short_esi is defined under the port_channel key, it will be overridden by the short_esi defined under ethernet_segment. Configuration using the new scheme is identical regardless of whether a port-channel or ethernet interface is being configured. Port-channels still require setting a port_channel key and mode subkey as before.

This model is designed to assume sensible defaults, allowing minimal configuration to be set in most cases, but always allowing for this behaviour to be overridden.

How to test

• A number of new molecule test cases have been added to the MH* leaf switches.
• A separate AVD inventory was used to test generated configuration in vEOS-lab.

Checklist

Repository Checklist

• My code has been rebased from devel before I start
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation and documentation have been updated accordingly.
• I have updated molecule CI testing accordingly. (check the box if not applicable)

[jonxstill]

Added support fordont_preempt.

[gmuloc]

LGTM

[github-actions]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[github-actions]

Conflicts have been resolved. A maintainer will review the pull request shortly.

[ClausHolbechArista]

LGTM