[Multicast] Add Multipath Support in Terraform Module

[camschaecisco]

IP Multicast Multipath Support

Add Terraform mapping logic to translate schema's multicast multipath configurations into the Terraform provider's iosxe_multicast resource attributes.

Schema Mappings

Global Multicast Configuration:
multicast.multipath → multipath
multicast.multipath_s_g_hash → multipath_s_g_hash

VRF-Specific Multicast Configuration:
multicast.vrfs[].vrf → vrfs[].vrf
multicast.vrfs[].multipath → vrfs[].multipath
multicast.vrfs[].multipath_s_g_hash → vrfs[].multipath_s_g_hash

Changes

Add new multicast resource module iosxe_multicast.tf:

• multipath (line 5) - Enable/disable multicast multipath globally
• multipath_s_g_hash (line 6) - S-G hash algorithm selection (basic, next-hop-based)
• vrfs (lines 8-12) - VRF-specific multicast multipath configuration
  • vrf (line 9) - VRF name
  • multipath (line 10) - Enable/disable multicast multipath in VRF
  • multipath_s_g_hash (line 11) - VRF-specific hash algorithm
• depends_on (lines 14-16) - VRF dependency management
• for_each (line 2) - Multi-device deployment support
• Support for device-specific, default, and null configuration values
• Three-tier fallback hierarchy: device config → global defaults → null
• Pre-commit hooks passed: terraform fmt, tflint, terraform-docs

This Enables Declarative Configuration of:

• IP multicast multipath load balancing across equal-cost paths (ECMP)
• Per-device multicast multipath policies with global default fallback
• Two s-g-hash algorithms (basic: source-based, next-hop-based: source+group+nexthop)
• VRF-aware multicast multipath for multi-tenancy environments
• Automatic VRF dependency management ensuring proper resource creation order
• Multi-device deployments from centralized YAML data models
• Network-wide multicast traffic distribution optimization
• Consistent multicast forwarding behavior across hybrid campus and data center fabrics
• GitOps workflows for multicast configuration management

Version Requirements

IOS-XE 17.12.1 and later:

• ✅ multipath - Enable/disable multicast multipath
• ✅ multipath_s_g_hash - S-G hash algorithm (basic, next-hop-based)
• ✅ vrfs - VRF-specific multicast multipath configuration

Platform Notes:

• Both Cat8k routers and Cat9k switches support all multicast multipath features
• YANG model validation confirms feature availability from IOS-XE 17.12.1

Example Configuration

Global Multicast Multipath:

iosxe:
  devices:
    - name: Cat8k-Router
      configuration:
        multicast:
          multipath: true
          multipath_s_g_hash: next-hop-based

VRF-Specific Multicast Multipath:
iosxe:
  devices:
    - name: Cat8k-Router
      configuration:
        multicast:
          multipath: true
          multipath_s_g_hash: basic
          vrfs:
            - vrf: VRF1
              multipath: true
              multipath_s_g_hash: next-hop-based
            - vrf: VRF2
              multipath: true
              multipath_s_g_hash: basic

Global Defaults:
iosxe:
  defaults:
    configuration:
      multicast:
        multipath: true
        multipath_s_g_hash: basic

Testing

Multi-Platform Validation
- Catalyst 8000V (Router, IOS-XE 17.15): ✅ Global and VRF multicast multipath deployed successfully
- Catalyst 9200L (Switch, IOS-XE 17.15): ✅ Global and VRF multicast multipath deployed successfully

Terraform Operations Verified
- ✅ terraform plan - Correctly identifies multicast configuration changes
- ✅ terraform apply - Successfully creates multicast multipath configuration
- ✅ terraform destroy - Cleanly removes multicast configuration
- ✅ Device verification - All multicast multipath settings present in running-config
- ✅ State management - Proper resource state tracking across lifecycle

Pre-commit Quality Checks
Terraform fmt............................................................Passed
Terraform validate with tflint...........................................Passed
terraform-docs...........................................................Passed
terraform-docs...........................................................Passed
terraform-docs...........................................................Passed
terraform-docs...........................................................Passed