Damien/arista-evpn-vxlan-clab
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
96244df528a542a6782d298bdda949135fa6ee0c
arista-evpn-vxlan-clab/docs/fabric-standardization.md
Damien Arnodo 96244df528 docs: rework naming conventions with structured hostname format (Phase 0 - #31) 
Format: <SITE>-<ZONE>-<ROLE>-<ID> (e.g., PA-DC-LEAF-01)
- Site prefix registry (2 chars: PA, LY, MA...)
- Zone codes: DC, DR, LAB, CO
- Interface descriptions reference full hostnames
- MLAG domain-id now unique per pair
- IPAM identifiers aligned with new naming
- BGP session descriptions standardized
2026-03-15 16:01:55 +00:00

13 KiB
Raw Blame History

Fabric Standardization — Small EVPN-VXLAN Data Centers

Status: Draft — Phase 0 (#31) Scope: POC for small data centers (2 spines, 3-8 leafs) Parent: Epic #30

1. Topology constraints

1.1 Spine layer

  • Always 2 spines per fabric (redundancy, no single point of failure)
  • Spines are pure L3 routers — no VTEPs, no VLANs, no MLAG
  • Each spine connects to every leaf via a dedicated P2P link

1.2 Leaf layer

  • Leafs always come in MLAG pairs (2 leafs = 1 VTEP)
  • Minimum 3 pairs (6 leafs), maximum 4 pairs (8 leafs) per fabric
  • Each leaf connects to both spines via dedicated uplinks
  • Each leaf pair shares a VTEP loopback IP (Loopback1)

1.3 Host connectivity

  • Hosts connect directly to leaf pairs — no access switches
  • Every host is dual-homed via MLAG (LACP active)
  • Each host-facing port-channel gets a unique MLAG ID

1.4 Containerlab model

  • All devices use the ceos image (Arista cEOS)
  • The lab simulates a fixed 12-port model per device

2. Port assignment — Spine

Spines use a simple sequential mapping: one Ethernet port per leaf.

Port Role Connected to
Ethernet1 Underlay downlink Leaf 01
Ethernet2 Underlay downlink Leaf 02
Ethernet3 Underlay downlink Leaf 03
... ... ...
Ethernet{N} Underlay downlink Leaf {N}

All spine downlinks are:

  • Routed (no switchport)
  • /31 P2P addressing
  • MTU 9214 (jumbo frames for VXLAN encapsulation)

3. Port assignment — Leaf

Leaf port allocation follows a fixed layout. Ports are divided into 3 zones:

Port range Role Details
Ethernet1 — Ethernet9 Host-facing MLAG port-channels (trunk, LACP active)
Ethernet10 MLAG peer-link Port-Channel999 (trunk, trunk-group mlag-peer)
Ethernet11 Spine1 uplink Routed P2P /31, MTU 9214
Ethernet12 Spine2 uplink Routed P2P /31, MTU 9214

3.1 Host-facing ports (Ethernet1-9)

  • Each physical port is a member of a Port-Channel
  • Port-Channel number = MLAG ID = host index (e.g., host 01 → Po1, MLAG 1)
  • Mode: switchport mode trunk
  • VLANs: only the VLANs needed by the host
  • LACP fallback enabled (timeout 5, individual)

3.2 MLAG peer-link (Ethernet10)

  • Always Port-Channel999
  • Trunk mode with trunk-group mlag-peer
  • Spanning-tree link-type point-to-point
  • Carries MLAG control traffic + VLANs 4090, 4091

3.3 Spine uplinks (Ethernet11-12)

  • Ethernet11 → spine 01, Ethernet12 → spine 02
  • Fixed mapping, never changes regardless of fabric size

4. Naming conventions

4.1 Device hostname format

All device hostnames follow the pattern:

<SITE>-<ZONE>-<ROLE>-<ID>
Field Length Description Values
SITE 2 chars City / location code (uppercase) PA (Paris), LY (Lyon), MA (Marseille), LO (London)...
ZONE 2-3 chars Network area (uppercase) DC (Datacenter), DR (Disaster Recovery), LAB (Lab), CO (Colocation)
ROLE 4-5 chars Device function (uppercase) SPINE, LEAF, HOST
ID 2 digits Sequential number (zero-padded) 01, 02, ..., 99

Examples for Paris datacenter:

Device Hostname
Spine 1 PA-DC-SPINE-01
Spine 2 PA-DC-SPINE-02
Leaf 1 (pair 1, primary) PA-DC-LEAF-01
Leaf 2 (pair 1, secondary) PA-DC-LEAF-02
Leaf 3 (pair 2, primary) PA-DC-LEAF-03
Leaf 4 (pair 2, secondary) PA-DC-LEAF-04
Host 1 PA-DC-HOST-01

Examples for Lyon disaster recovery:

Device Hostname
Spine 1 LY-DR-SPINE-01
Leaf 1 LY-DR-LEAF-01

4.2 Leaf pairing rule

Leafs are numbered sequentially. Odd = primary, even = secondary within a pair:

Pair Primary Secondary VTEP
1 {SITE}-{ZONE}-LEAF-01 {SITE}-{ZONE}-LEAF-02 VTEP 1
2 {SITE}-{ZONE}-LEAF-03 {SITE}-{ZONE}-LEAF-04 VTEP 2
3 {SITE}-{ZONE}-LEAF-05 {SITE}-{ZONE}-LEAF-06 VTEP 3
4 {SITE}-{ZONE}-LEAF-07 {SITE}-{ZONE}-LEAF-08 VTEP 4

4.3 Fabric name

The fabric is identified by {SITE}-{ZONE} (lowercase in Infrahub objects):

Infrahub object Name Example
InfraFabric {site}-{zone} pa-dc
LocationSite {site}-{zone} pa-dc

4.4 Interface descriptions

Interface descriptions reference the full hostname of the remote device:

Interface Description format Example (on PA-DC-LEAF-01)
Spine uplink Eth11 to {REMOTE_HOSTNAME} to PA-DC-SPINE-01
Spine uplink Eth12 to {REMOTE_HOSTNAME} to PA-DC-SPINE-02
MLAG peer-link Eth10 mlag peer link mlag peer link
Host-facing Eth1 to {HOST_HOSTNAME} to PA-DC-HOST-01
Loopback0 Router-ID Router-ID
Loopback1 VTEP VTEP

On spines:

Interface Description format Example (on PA-DC-SPINE-01)
Downlink Eth1 to {REMOTE_HOSTNAME} to PA-DC-LEAF-01
Loopback0 Router-ID Router-ID

4.5 MLAG domain

Parameter Value Notes
Domain ID {site}-{zone}-pair{NN} e.g., pa-dc-pair01 — unique per MLAG pair
Peer-link Port-Channel999 Fixed
Peer-link VLAN 4090 Fixed
iBGP peering VLAN 4091 Fixed

4.6 BGP descriptions

Session type Description format Example
eBGP underlay underlay to {REMOTE_HOSTNAME} underlay to PA-DC-SPINE-01
iBGP MLAG peer ibgp to {REMOTE_HOSTNAME} ibgp to PA-DC-LEAF-02
EVPN overlay evpn to {REMOTE_HOSTNAME} evpn to PA-DC-SPINE-01

4.7 IPAM identifiers (for resource pool idempotence)

All identifiers use lowercase, with the fabric name {site}-{zone}:

Object Identifier pattern Example
Site infra prefix site-{site}-{zone}-infra site-pa-dc-infra
Site services prefix site-{site}-{zone}-services site-pa-dc-services
Device loopback0 IP lo0-{site}-{zone}-{role}-{id} lo0-pa-dc-leaf-01
Device loopback1 IP lo1-{site}-{zone}-vtep{NN} lo1-pa-dc-vtep01
Underlay P2P /31 p2p-{site}-{zone}-spine{NN}-leaf{NN} p2p-pa-dc-spine01-leaf01
MLAG peer /31 mlag-peer-{site}-{zone}-pair{NN} mlag-peer-pa-dc-pair01
MLAG iBGP /31 mlag-ibgp-{site}-{zone}-pair{NN} mlag-ibgp-pa-dc-pair01
Leaf ASN asn-{site}-{zone}-pair{NN} asn-pa-dc-pair01

4.8 Site prefix registry

To avoid conflicts, site prefixes must be registered:

Prefix City Country
PA Paris FR
LY Lyon FR
MA Marseille FR
LO London UK
FR Frankfurt DE
AM Amsterdam NL

This registry is maintained as a reference. The SITE code is stored on the LocationSite object in Infrahub.

5. IPAM — IP addressing plan

5.1 Supernets (global)

Role Supernet Description
Infrastructure 10.0.0.0/8 Loopbacks, underlay, MLAG
Services 172.16.0.0/12 L2/L3 VXLAN user subnets

5.2 Site allocation (from supernets)

Each site receives:

  • 1x /16 from 10.0.0.0/8 for infrastructure
  • 1x /16 from 172.16.0.0/12 for services

5.3 Fabric pools (from site infra /16)

Pool Prefix size Allocation unit Pool type
Loopback0 (router-id) /24 /32 per device CoreIPAddressPool
Loopback1 (VTEP) /24 /32 per MLAG pair CoreIPAddressPool
Underlay P2P /24 /31 per spine-leaf link CoreIPPrefixPool
MLAG peer-link SVI /24 /31 per MLAG pair CoreIPPrefixPool
MLAG iBGP peering /24 /31 per MLAG pair CoreIPPrefixPool

5.4 Service pools (from site services /16)

Pool Allocation unit Pool type
L2 VXLAN subnets /24 per VLAN (customizable) CoreIPPrefixPool
L3 VXLAN subnets (VRF SVIs) /24 per VRF SVI (customizable) CoreIPPrefixPool

5.5 Special VLANs (reserved, not from pools)

VLAN Name Purpose Trunk group
4090 mlag-peer MLAG peer-link SVI mlag-peer
4091 mlag-ibgp MLAG iBGP peering mlag-peer

6. BGP — Autonomous System assignment

6.1 Spine ASN

  • Single ASN shared by all spines in a fabric
  • Defined as an attribute on InfraFabric
  • Default for POC: 65000

6.2 Leaf ASN

  • One ASN per MLAG pair (iBGP within pair, eBGP to spines)
  • Allocated from a CoreNumberPool (range: 65001–65099)
  • Deterministic via identifier: asn-{site}-{zone}-pair{NN}

6.3 BGP configuration standards

Parameter Value Notes
no bgp default ipv4-unicast Always Explicit activation per AFI
distance bgp 20 200 200 eBGP preferred over iBGP
maximum-paths 4 ecmp 64 Multi-path for spine redundancy
maximum-routes 12000 warning-only Per neighbor
ebgp-multihop 3 EVPN overlay (loopback peering)
send-community extended Always Required for EVPN route-targets
next-hop-unchanged Spine EVPN peer-group Preserve leaf next-hop in overlay
next-hop-self Leaf iBGP peer-group Required for iBGP convergence

6.4 Peer groups (per device)

Leaf peer groups:

Peer group Type Remote AS Neighbors
underlay eBGP spine ASN Spine P2P IPs
underlay_ibgp iBGP own ASN MLAG peer via VLAN 4091
evpn eBGP spine ASN Spine loopback0 IPs

Spine peer groups:

Peer group Type Neighbors
evpn eBGP All leaf loopback0 IPs (each with its own remote-as)

Spine underlay neighbors are configured individually (no peer-group) since each leaf has a different ASN.

6.5 Address families

AFI Activated on Networks advertised
IPv4 unicast underlay, underlay_ibgp Loopback0/32, Loopback1/32
EVPN evpn (routes from VLAN/VRF config)

7. MLAG standards

Parameter Value
Domain ID {site}-{zone}-pair{NN} (e.g., pa-dc-pair01)
Peer-link interface Port-Channel999
Peer-link VLAN 4090 (IP: /31 from MLAG peer pool)
iBGP VLAN 4091 (IP: /31 from MLAG iBGP pool, MTU 9214)
Peer VLAN autostate Disabled (no autostate)
Dual-primary detection Enabled (delay 10, errdisable all-interfaces)
Heartbeat Via Management0 (VRF mgmt)
Virtual MAC c001.cafe.babe (fabric-wide anycast gateway)

7.1 Primary/secondary assignment

  • Odd-numbered leaf (LEAF-01, LEAF-03, LEAF-05, LEAF-07): lower IP on MLAG VLANs (e.g., x.x.x.0/31)
  • Even-numbered leaf (LEAF-02, LEAF-04, LEAF-06, LEAF-08): higher IP (e.g., x.x.x.1/31)

8. VXLAN standards

8.1 VTEP interface

  • Interface: Vxlan1 on every leaf
  • Source interface: Loopback1 (shared IP within MLAG pair)
  • UDP port: 4789
  • Learning: vxlan learn-restrict any (EVPN-controlled)

8.2 VNI allocation

Type NumberPool range Usage
L2 VNI 100001–199999 One VNI per extended VLAN (EVPN Type-2)
L3 VNI 200001–299999 One VNI per VRF (EVPN Type-5)

VNIs are allocated from CoreNumberPool with deterministic identifiers.

8.3 Route distinguisher and route target

Service type RD format RT format
L2 VXLAN (per VLAN) {ASN}:{VNI} {VLAN_ID}:{VNI} (import/export)
L3 VXLAN (per VRF) {Loopback0_IP}:{VRF_index} {VRF_index}:{VNI} (import/export evpn)

9. Global parameters

Parameter Value Notes
Underlay MTU 9214 All P2P and iBGP links
Anycast gateway MAC c001.cafe.babe ip virtual-router mac-address
Routing model multi-agent service routing protocols model multi-agent
Spanning-tree Disabled on VLAN 4090, 4091 MLAG VLANs only
LLDP Management0 lldp management-address Management0
gNMI Enabled management api gnmi with provider eos-native

10. Out of scope (for now)

  • Access switches — hosts connect directly to leafs
  • Multi-fabric / DCI — single fabric per site
  • IPv6 underlay — IPv4 only
  • BFD — not configured in initial POC
  • Route-maps / prefix-lists — no filtering in the underlay
  • More than 2 spines — fixed at 2 for the POC
  • Non-Arista platforms — EOS only
Reference in New Issue View Git Blame Copy Permalink