What are Virtual Networks

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The way the description is rendered in a configuration depends on the NOS of the device:

• Junos - Description is rendered under VLAN configuration (It's always present.)

• SONiC - No description is rendered.

• NX-OS - Description is rendered only on SVI, unless the IP address is disabled, then no description is rendered.

• EOS - Description is rendered only on SVI, unless the IP address is disabled, then no description is rendered.

• VLAN (rack-local VN)
• VXLAN (EVPN) (inter-rack VN)

Tags

• VLAN - default routing zone only (used for the underlay network)
• VXLAN - default routing zone or user-defined routing zone

• Layer 2 VLAN ID on the switch that the VN is assigned to.

• If left blank, it's auto-assigned from static pool (2-4094).

• If you assign it, we don't recommend assigning VLAN ID 1 for active VNs.

• Cisco NX-OS reserves VLAN IDs 3968-4094.

• Arista reserves 1006-4094 for internal VLANs for routed ports. You can modify "reserved" VLAN ID range with the EOS vlan internal allocation policy configuration command. You can apply it to all EOS devices using a SYSTEM configlet before configuring and deploying VNs.

  l2-virtual-ext-002-leaf1(config)#vlan internal allocation policy ascending range 3001 3999
  l2-virtual-ext-002-leaf1(config)#exit
  l2-virtual-ext-002-leaf1#show vlan internal allocation policy
  Internal VLAN Allocation Policy: ascending
  Internal VLAN Allocation Range: 3001-3999
  l2-virtual-ext-002-leaf1#

• Using reserved VLAN IDs may cause deployment errors, but not build errors.

• IPv4 subnet - (for example: 192.168.100.0/24) (can't use batching VLANs)
• IPv4 CIDR length - automatically assigns a subnet with the specified length (for example: /26)
• If left blank, it's auto-assigned a /24 subnet network from resource pools

• IPv6 subnet (for example: 2001:4de0::/64)
• IPv6 CIDR length - automatically assigns a subnet with the specified length (for example: /56)
• If left blank, it's auto-assigned a /64 subnet network from resource pools.
• If assigned automatically, the IP is derived from the assigned VNs SVI pools.
• To assign multiple VLAN networks, leave blank or specify CIDR length.

• Tagged
• Untagged

5-stage Clos networks include pods, and you can select leaf devices within each pod to extend VNs to those devices.

The racks assigned. For MLAG racks, the leaf pair is shown. For VLANs, if more than one rack is selected, multiple rack-local VLAN-based VNs are created.

Leverage system tags for filtering when you create virtual networks. This helps speed-up the definition of a virtual network footprint in large-scale deployment. It nicely complements the tag-driven interface assignment at the connectivity template level.

Label assigned to rack (for example, ext-link-1, single-link, single-link, ext-link-0)

Can use for batch creating VNs

• Enabled (default) - Apstra decides whether a secondary IP address is needed.

  • Automatically allocate if an assigned connectivity template requires an address (BGP, Static routes).

  • VN of type VXLAN:

    • Some NOS types automatically allocate unicast IPv4 addresses when an anycast IPv4 gateway is present: (Junos when in an ESI pair).

    • If a NOS type forbids co-existence of an anycast IPv4 address with an unicast IPv4 address, a blueprint error will be raised (Sonic).

  • VN of type VLAN - All NOS types require unicast IPv4 addresses when the IPv4 anycast address is enabled.

• Forced - A secondary IP address is rendered irrespective of whether or not a connectivity template requires it.

  • If a NOS type forbids co-existence of an anycast IPv4 address with a unicast IPv4 address, a blueprint error will be raised.

  • Permits you to manually create an optional unicast IPv4 address for purposes such as BGP peering or static routing.