L3 Overlay (L3VNI)¶

L3 Overlay is L3 network only without L2 stretching over the fabric.

Inputs¶

Inventory.yml¶

In the inventory file, roles (Spine or Leaf), names, and management IP addresses of the nodes are described.

all:
  children:
    leaf:
      hosts:
        Leaf-01:
          ansible_host: 10.1.1.1
        Leaf-02:
          ansible_host: 10.1.1.2

    spine:
      hosts:
        Spine-01:
          ansible_host: 10.1.1.3
        Spine-02:
          ansible_host: 10.1.1.3

leaf and spine are two roles. Each node should be placed under one of these roles.

Leaf-1 , Spine-01 are the hostnames (nodes). Keep in mind that the names should be with the name of the configuration files in the directory host_vars.

ansible_host is the IP address of the management interface.

group_vars¶

This directory contains the configurations which are common to all or most of devices.

all.yml¶

The parameters defined in the file all.yml are applicable to all devices in the network.

General access¶

This section defines access parameters of the remote devices.

ansible_connection: ansible.netcommon.network_cli
ansible_network_os: cisco.ios.ios
ansible_python_interpreter: "python"
ansible_user: cisco
ansible_ssh_pass: cisco123

<...skip...>

Parameter	Comments
ansible_connection	This option defines thetype for connection to the remote devices. In this project, connection via SSH with implementation of CLI is used: ansible.netcommon.network_cli
ansible_network_os	This option defines the operation system of the remote device. This option is needed if “network_cli” is used for ‘ansible_connection’. In this project, Cat9k with IOS-XE is used, so this option is set to: cisco.ios.ios
ansible_python_interpreter	This option instruct Ansible to use defined python interpreter. This option is set to: python
ansible_user	This option defines a username which is used for access remote devices over SSH. In this project, user must have privilege level 15. This option is set to: cisco
ansible_password	This option defines a password for the user in ‘ansible_user’. In this project, the password is set to: cisco123

Warning

ansible_user must have privildge level 15. Example of the configuration is below

username cisco privilege 15 password 0 cisco123

In this example, unencrypted password is used. Feel free to use HIDDEN (7)

If enable password should be used, check the Enable Mode documentation.

overlay_db.yml¶

In this file information about EVPN configuration is stored. Let’s check this file gradually step-by-step.

L2VPN EVPN general definition¶

This section defines global L2VPN EVPN parameters.

l2vpn_global:
  router_id: 'Loopback1'

<...skip...>

Parameter

Comments

l2vpn_global / mandatory

This option defines L2VPN EVPN globally.

router_id / optional

This option defines the interface whose IP address will be used for defining router-id of L2VPN.The interface Loopback1 is used for the router-id of L2VPN.

In this project the option is set to:

Loopback1

VRF definition¶

This section defines vrf parameters. Lets review parameters for unicast first.

vrfs:
  green:
    rd: '1:1'
      afs:
        ipv4:
          rt_import:
            - '1:1'
            - '1:1 stitching'
          rt_export:
            - '1:1'
            - '1:1 stitching'
        ipv6:
          rt_import:
            - '1:1'
            - '1:1 stitching'
          rt_export:
            - '1:1'
            - '1:1 stitching'
<...skip...>

Parameter	Comments
vrfs / mandatory	This option defines the vrf section.
<vrf_name> / mandatory	This option defines the vrf name.
rd / mandatory	This option defines the route distinguisher of the vrf.
afs / mandatory	This option defines the address families which will be activated for the vrf. Option ipv4 defines ipv4 address family. Option ipv6 defines ipv6 address family. Choices: ipv4 ipv6
rt_import / mandatory	This option defines the Route Target Import per VRF/AF. This option allows more than one RT to be defined. For EVPN AF additional key is used - “stitching”. In this project next parameter are set by default for both AFs(IPv4 and IPv6): 1:1 1:1 stitching (L2VPN EVPN AF)
rt_export / mandatory	This option defines the Route Target Export per VRF/AF. This option allows more than one RT to be defined. For EVPN AF, additional key “stitching” is used. In this project below parameters are set by default for both AFs(IPv4 and IPv6): 1:1 1:1 stitching (L2VPN EVPN AF)

VLANs section¶

This section defines the VLANs and their stitching with EVIs (EVPN instance) and VNIs (VXLAN network identifier).

vlans:

  901:
    vlan_type: 'core'
    description: 'Core_VLAN_VRF_green'
    vni: '50901'
    vrf: 'green'

<...snip...>

Parameter	Comments
vlans / mandatory	This option defines the VLAN section.
<vlan_id> / mandatory	This option defines the VLAN ID. In the example shown, VLAN IDs are 101, 102, 901.
vlan_type / mandatory	This option defines the VLAN type. Option core is used for L3VNIs. Choices core
description / optional	This option defines the VLAN description.
vni / mandatory	This option defines the VNI which is stitched with the VLAN ID on the switch.
vrf / mandatory	This option defines the VRF that uses the VLAN’s L3VNI for encapsulating the routed traffic in the core. For this option, vlan_type must be core. This parameter is mandatory for L3VNIs only.

SVIs section¶

This section defines SVIs configuration.

svis:

  901:
    svi_type: 'core'
    vrf: 'green'
    src_intf: 'Loopback1'
    ipv6_enable: 'yes

<...snip...>

Parameter	Comments
svis / mandatory	This option defines SVIs section.
<svi_id> / mandatory	This option defines the SVI ID on the switch. In this example, there are 101, 102, 901.
svi_type / mandatory	This option defines the SVI type. Option core is used when the VLAN associated with an SVI is stitched to L3VNIs. Choices core
vrf / mandatory	This option defines the vrf which SVI belongs to.
src_intf / mandatory	This option defines thee source Interface for the SVI for L3VNI. This parameter is applicable for L3VNI SVIs only.
ipv6_enable / optional	This option defines enables IPv6 on the SVI. This parameter is applicable for L3VNI SVIs only.

NVE section¶

This section defines the NVE interface configuration.

nve_interfaces:
  1:
    source_interface: 'Loopback1'

<...snip...>

host_vars¶

This directory contains configuration specific to a device.

<node_name>.yml¶

The file <node_name>.yml contains configurations, usually the ones related to interface and underlay, specific to a node.

Let us review the configuration in <node_name>.yml.

Hostname section¶

This section defines the hostname of a node.

hostname: 'Leaf-01'

<...snip...>

Parameter	Comments
hostname / optional	This option defines the remote device’s hostname.

Global routing section¶

In this section, IPv4/IPv6 related parameters for global routing table are defined.

Parameter	Comments
routing / mandatory	This option defines the global routing section.
ipv4_uni / mandatory	This option enables the global IPv4 unicast routing on the device.
ipv6_uni / mandatory	This option enables the global IPv6 unicast routing on the device.
ipv6_multi / mandatory	This option enables the global IPv4 multicast routing on the device.

Interface section¶

In this section, the configurations of the interfaces are defined.

interfaces:

  Loopback0:
    name: 'Routing Loopback'
    ip_address: '172.16.255.3'
    subnet_mask: '255.255.255.255'
    loopback: 'yes'
    pim_enable: 'no'

  Loopback1:
    name: 'NVE Loopback'
    ip_address: '172.16.254.3'
    subnet_mask: '255.255.255.255'
    loopback: 'yes'
    pim_enable: 'yes'

  GigabitEthernet1/0/1:
    name: 'Backbone interface to Spine-01'
    ip_address: '172.16.13.3'
    subnet_mask: '255.255.255.0'
    loopback: 'no'
    pim_enable: 'yes'

  GigabitEthernet1/0/2:
    name: 'Backbone interface to Spine-02'
    ip_address: '172.16.23.3'
    subnet_mask: '255.255.255.0'
    loopback: 'no'
    pim_enable: 'yes'

<...snip...>

Parameter	Comments
interfaces / mandatory	This option defines the interface section.
<interface_name> / mandatory	This option defines the interface name. For example: `Loopback0` or `GigabitEthernet1/0/1`
name / optional	This option defines the interface description.
ip_address / mandatory	This option defines the IPv4 address on the interface.
subnet_mask / mandatory	This option defines the subnet mask for the IPv4 address.
loopback / mandatory	This option tells whether the interface is loopback or not. Choices: yes no
pim_enable / mandatory	This option tells whether PIM must be enabled on the interface. Choices: yes no

OSPF section¶

This section defines the OSPF parameters.

By default, next OSPF configurations are applied:

Interface network type - point-to-point
OSPF process ID - 1
OSPF area number - 0

OSPF router-id is a configurable parameter.

ospf:
  router_id: '172.16.255.3'

<...snip...>

Parameter	Comments
ospf / mandatory	This option defines the OSPF section.
router_id / mandatory	This option defines the OSPF router-id.

PIM section¶

This section defines global PIM parameters. This section is optional if Ingress-Replication in the core is used.

pim:
  rp_address: '172.16.255.255'

<...skip...>

Parameter	Comments
pim / mandatory	This option defines the PIM section.
rp_address / mandatory	This option defines the RP address.

MSDP section¶

This section defines the MSDP parameters. Usually, MSDP is used for configuration RP redundancy in the underlay.

This section is optional.

msdp:
  '1':
    peer_ip: '172.16.254.2'
    source_interface: 'Loopback1'
    remote_as: '65001'

<...skip...>

Parameter	Comments
msdp / mandatory	This option defines the MSDP section.
<msdp_neighbor_id> / mandatory	This option defines ID for the MSDP peer. This number is not used in the switch configuration, just index number.
peer_ip / :red: mandatory	This option defines the MSDP peer’s IPv4 address.
source_interface / :red: mandatory	This option defines the IP address of the source interface which will be used as a source IP for the MSDP session.
remote_as / :red: mandatory	This option is used for defining the BGP AS number of the MSDP peer.

BGP section¶

This section defines BGP parameters.

By default next design assumption are made:

Leafs are Route-Reflector clients
Two present Spines in the topology are Route-Reflectors

bgp:
  as_number: '65001'
  router_id: 'Loopback0'
  neighbors:
    '172.16.255.1':
      peer_as_number: '65001'
      source_interface: 'Loopback0'

    '172.16.255.2':
      peer_as_number: '65001'
      source_interface: 'Loopback0'

    '172.16.255.3':
      peer_as_number: '65001'
      source_interface: 'Loopback0'
      rrc: 'yes'

<...snip...>

Parameter	Comments
bgp / mandatory	This option defines BGP section globally.
as_number / mandatory	This option defines BGP AS number.
router_id / mandatory	This option defines interface which ip address will be used like BGP router ID.
neighbors / mandatory	This option defines neighbors section.
neigbor_ip_address / mandatory	This option defines BGP neighbor ip address
peer_as_number / mandatory	This option defines BGP neighbor AS number
source_interface / mandatory	This option defines source interface which ip address will be used like a SRC IP for BGP session.
rrc / optional	This option defines the peer like a BGP route-reflector client.