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4.5 Underlay Network Provisioning

4.5.1 Underlay Design Principles

Design Overview

The underlay network provides Layer 3 IP connectivity between all fabric nodes. It uses IS-IS as the routing protocol with BFD for fast failure detection.

┌─────────────────────────────────────────────────────────────────────────────┐
│                        UNDERLAY DESIGN PRINCIPLES                           │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  ROUTING PROTOCOL: IS-IS (Level-2 Only)                                    │
│  ─────────────────────────────────────                                      │
│  • Single area per fabric site                                              │
│  • Wide metrics enabled                                                     │
│  • Point-to-point links (no DR/BDR election)                               │
│  • BFD for sub-second failover                                             │
│  • Authentication: HMAC-SHA-256                                            │
│                                                                             │
│  ADDRESSING:                                                                │
│  ───────────                                                                │
│  • Loopbacks: 10.250.0.0/16 (RLOC addresses)                               │
│  • P2P Links: 10.251.0.0/16 (/31 per link)                                 │
│  • Management: 10.252.0.0/16 (OOB management)                              │
│                                                                             │
│  MTU REQUIREMENTS:                                                          │
│  ─────────────────                                                          │
│  • Fabric links: 9100 bytes minimum                                        │
│  • VXLAN overhead: 50 bytes                                                │
│  • Original frame: 1500 bytes                                              │
│  • Total required: 1500 + 50 = 1550 (9100 provides headroom)              │
│                                                                             │
│  CONVERGENCE TARGETS:                                                       │
│  ────────────────────                                                       │
│  • Link failure detection: <100ms (BFD)                                    │
│  • Routing convergence: <1 second                                          │
│  • End-to-end failover: <2 seconds                                         │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

Underlay Topology Per Site Type

Hub Site Topology (Full Mesh Core)

┌─────────────────────────────────────────────────────────────────────────────┐
│                    HUB SITE UNDERLAY TOPOLOGY                               │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│                          WAN / SD-WAN                                       │
│                              │                                              │
│            ┌─────────────────┴─────────────────┐                           │
│            │                                   │                           │
│      ┌─────┴─────┐                       ┌─────┴─────┐                     │
│      │ BORDER-1  │═══════════════════════│ BORDER-2  │                     │
│      │ Lo0: .1   │      10G P2P          │ Lo0: .2   │                     │
│      └─────┬─────┘                       └─────┬─────┘                     │
│            │╲                               ╱│                             │
│            │ ╲         Full Mesh          ╱ │                             │
│            │  ╲         10G P2P          ╱  │                             │
│            │   ╲                        ╱   │                             │
│      ┌─────┴─────┐                 ┌────┴──────┐                          │
│      │   CP-1    │═════════════════│   CP-2    │                          │
│      │ Lo0: .3   │     10G P2P     │ Lo0: .4   │                          │
│      └─────┬─────┘                 └─────┬─────┘                          │
│            │                             │                                 │
│            │     Distribution Layer      │                                 │
│            │      (L3 to Access)         │                                 │
│            │                             │                                 │
│    ┌───────┴───────┬───────────┬────────┴───────┐                        │
│    │               │           │                │                        │
│ ┌──┴───┐      ┌───┴──┐   ┌───┴──┐        ┌───┴──┐                       │
│ │Edge-1│      │Edge-2│   │Edge-3│  ...   │Edge-N│                       │
│ │Lo0:.5│      │Lo0:.6│   │Lo0:.7│        │Lo0:.N│                       │
│ └──────┘      └──────┘   └──────┘        └──────┘                       │
│                                                                             │
│  Link Types:                                                                │
│  ═══════ = 10G/25G P2P Links (IS-IS)                                      │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

Branch Site Topology (Fabric-in-a-Box)

┌─────────────────────────────────────────────────────────────────────────────┐
│                    BRANCH SITE UNDERLAY TOPOLOGY                            │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│                          SD-WAN Edge                                        │
│                              │                                              │
│                        ┌─────┴─────┐                                       │
│                        │  FiaB-1   │═══════════┐                           │
│                        │(Border+CP)│           │ StackWise                 │
│                        │ Lo0: .1   │     ┌─────┴─────┐                     │
│                        └─────┬─────┘     │  FiaB-2   │                     │
│                              │           │(Border+CP)│                     │
│                              │           │ Lo0: .2   │                     │
│                              │           └─────┬─────┘                     │
│                              │                 │                           │
│                    ┌─────────┴─────────────────┘                           │
│                    │                                                        │
│            ┌───────┴───────┬───────────┐                                   │
│            │               │           │                                   │
│        ┌───┴──┐       ┌───┴──┐   ┌───┴──┐                                 │
│        │Edge-1│       │Edge-2│   │Edge-N│                                 │
│        │Lo0:.3│       │Lo0:.4│   │Lo0:.N│                                 │
│        └──────┘       └──────┘   └──────┘                                 │
│                                                                             │
│  Note: FiaB nodes combine Border, CP, and can also serve as Edge          │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

4.5.2 Complete IP Addressing Scheme

Loopback Address Allocation (10.250.0.0/16)

Address Format: 10.250.{site-id}.{node-id}/32

Region Site Site ID Address Range Capacity
APAC Mumbai 1 10.250.1.0/24 254 nodes
APAC Chennai 2 10.250.2.0/24 254 nodes
APAC Bangalore 3 10.250.3.0/24 254 nodes
APAC Delhi 4 10.250.4.0/24 254 nodes
APAC Noida 5 10.250.5.0/24 254 nodes
EMEA London 16 10.250.16.0/24 254 nodes
EMEA Frankfurt 17 10.250.17.0/24 254 nodes
EMEA Paris 18 10.250.18.0/24 254 nodes
EMEA Amsterdam 19 10.250.19.0/24 254 nodes
EMEA Dublin 20 10.250.20.0/24 254 nodes
AMER New Jersey 32 10.250.32.0/24 254 nodes
AMER Dallas 33 10.250.33.0/24 254 nodes
AMER Chicago 34 10.250.34.0/24 254 nodes
AMER Seattle 35 10.250.35.0/24 254 nodes
AMER Los Angeles 36 10.250.36.0/24 254 nodes

Node ID Assignment Standard

Node Type Node ID Range Example (Mumbai)
Border Node 1 1 10.250.1.1/32
Border Node 2 2 10.250.1.2/32
Control Plane 1 3 10.250.1.3/32
Control Plane 2 4 10.250.1.4/32
Edge Nodes 5-200 10.250.1.5/32 - 10.250.1.200/32
Extended Nodes 201-250 10.250.1.201/32 - 10.250.1.250/32
Reserved 251-254 Future use

Complete Loopback Assignments - All Hub Sites

Mumbai (Site ID: 1)

Hostname Role Loopback0 Platform
MUM-BN-01 Border Node 10.250.1.1/32 C9500-48Y4C
MUM-BN-02 Border Node 10.250.1.2/32 C9500-48Y4C
MUM-CP-01 Control Plane 10.250.1.3/32 C9500-24Y4C
MUM-CP-02 Control Plane 10.250.1.4/32 C9500-24Y4C
MUM-ED-01 Edge Node 10.250.1.5/32 C9300-48UXM
MUM-ED-02 Edge Node 10.250.1.6/32 C9300-48UXM
MUM-ED-03 Edge Node 10.250.1.7/32 C9300-48UXM
MUM-ED-04 Edge Node 10.250.1.8/32 C9300-48UXM
MUM-ED-05 Edge Node 10.250.1.9/32 C9300-48UXM
MUM-ED-06 Edge Node 10.250.1.10/32 C9300-48UXM
MUM-ED-07 Edge Node 10.250.1.11/32 C9300-48UXM
MUM-ED-08 Edge Node 10.250.1.12/32 C9300-48UXM
... ... ... ...
MUM-ED-48 Edge Node 10.250.1.52/32 C9300-48U

Chennai (Site ID: 2)

Hostname Role Loopback0 Platform
CHN-BN-01 Border Node 10.250.2.1/32 C9500-48Y4C
CHN-BN-02 Border Node 10.250.2.2/32 C9500-48Y4C
CHN-CP-01 Control Plane 10.250.2.3/32 C9500-24Y4C
CHN-CP-02 Control Plane 10.250.2.4/32 C9500-24Y4C
CHN-ED-01 Edge Node 10.250.2.5/32 C9300-48UXM
... ... ... ...
CHN-ED-36 Edge Node 10.250.2.40/32 C9300-48U

London (Site ID: 16)

Hostname Role Loopback0 Platform
LON-BN-01 Border Node 10.250.16.1/32 C9500-48Y4C
LON-BN-02 Border Node 10.250.16.2/32 C9500-48Y4C
LON-CP-01 Control Plane 10.250.16.3/32 C9500-24Y4C
LON-CP-02 Control Plane 10.250.16.4/32 C9500-24Y4C
LON-ED-01 Edge Node 10.250.16.5/32 C9300-48UXM
... ... ... ...
LON-ED-42 Edge Node 10.250.16.46/32 C9300-48U

Frankfurt (Site ID: 17)

Hostname Role Loopback0 Platform
FRA-BN-01 Border Node 10.250.17.1/32 C9500-48Y4C
FRA-BN-02 Border Node 10.250.17.2/32 C9500-48Y4C
FRA-CP-01 Control Plane 10.250.17.3/32 C9500-24Y4C
FRA-CP-02 Control Plane 10.250.17.4/32 C9500-24Y4C
FRA-ED-01 Edge Node 10.250.17.5/32 C9300-48UXM
... ... ... ...
FRA-ED-28 Edge Node 10.250.17.32/32 C9300-48U

New Jersey (Site ID: 32)

Hostname Role Loopback0 Platform
NJ-BN-01 Border Node 10.250.32.1/32 C9500-48Y4C
NJ-BN-02 Border Node 10.250.32.2/32 C9500-48Y4C
NJ-CP-01 Control Plane 10.250.32.3/32 C9500-24Y4C
NJ-CP-02 Control Plane 10.250.32.4/32 C9500-24Y4C
NJ-ED-01 Edge Node 10.250.32.5/32 C9300-48UXM
... ... ... ...
NJ-ED-52 Edge Node 10.250.32.56/32 C9300-48U

Dallas (Site ID: 33)

Hostname Role Loopback0 Platform
DAL-BN-01 Border Node 10.250.33.1/32 C9500-48Y4C
DAL-BN-02 Border Node 10.250.33.2/32 C9500-48Y4C
DAL-CP-01 Control Plane 10.250.33.3/32 C9500-24Y4C
DAL-CP-02 Control Plane 10.250.33.4/32 C9500-24Y4C
DAL-ED-01 Edge Node 10.250.33.5/32 C9300-48UXM
... ... ... ...
DAL-ED-32 Edge Node 10.250.33.36/32 C9300-48U

Branch Site Loopback Assignments

Bangalore (Site ID: 3) - Fabric-in-a-Box

Hostname Role Loopback0 Platform
BLR-FIAB-01 FiaB (Border+CP) 10.250.3.1/32 C9300-48UXM
BLR-FIAB-02 FiaB (Border+CP) 10.250.3.2/32 C9300-48UXM
BLR-ED-01 Edge Node 10.250.3.3/32 C9300-24U
BLR-ED-02 Edge Node 10.250.3.4/32 C9300-24U
BLR-ED-03 Edge Node 10.250.3.5/32 C9300-24U
BLR-ED-04 Edge Node 10.250.3.6/32 C9300-24U
BLR-ED-05 Edge Node 10.250.3.7/32 C9300-24U
BLR-ED-06 Edge Node 10.250.3.8/32 C9300-24U
BLR-ED-07 Edge Node 10.250.3.9/32 C9300-24U
BLR-ED-08 Edge Node 10.250.3.10/32 C9300-24U

Delhi (Site ID: 4) - Fabric-in-a-Box

Hostname Role Loopback0 Platform
DEL-FIAB-01 FiaB (Border+CP) 10.250.4.1/32 C9300-48UXM
DEL-FIAB-02 FiaB (Border+CP) 10.250.4.2/32 C9300-48UXM
DEL-ED-01 Edge Node 10.250.4.3/32 C9300-24U
DEL-ED-02 Edge Node 10.250.4.4/32 C9300-24U
DEL-ED-03 Edge Node 10.250.4.5/32 C9300-24U
DEL-ED-04 Edge Node 10.250.4.6/32 C9300-24U
DEL-ED-05 Edge Node 10.250.4.7/32 C9300-24U
DEL-ED-06 Edge Node 10.250.4.8/32 C9300-24U

Noida (Site ID: 5) - Fabric-in-a-Box

Hostname Role Loopback0 Platform
NOI-FIAB-01 FiaB (Border+CP) 10.250.5.1/32 C9300-24UXM
NOI-FIAB-02 FiaB (Border+CP) 10.250.5.2/32 C9300-24UXM
NOI-ED-01 Edge Node 10.250.5.3/32 C9200-24P
NOI-ED-02 Edge Node 10.250.5.4/32 C9200-24P

P2P Address Format

Format: 10.251.{site-id}.{link-id * 2}/31

Each /31 provides 2 addresses: - Even address (.0, .2, .4, etc.) = Lower node ID - Odd address (.1, .3, .5, etc.) = Higher node ID

Link ID From Device From Interface From IP To Device To Interface To IP Speed
0 MUM-BN-01 Te1/0/1 10.251.1.0/31 MUM-BN-02 Te1/0/1 10.251.1.1/31 10G
1 MUM-BN-01 Te1/0/2 10.251.1.2/31 MUM-CP-01 Te1/0/1 10.251.1.3/31 10G
2 MUM-BN-01 Te1/0/3 10.251.1.4/31 MUM-CP-02 Te1/0/1 10.251.1.5/31 10G
3 MUM-BN-02 Te1/0/2 10.251.1.6/31 MUM-CP-01 Te1/0/2 10.251.1.7/31 10G
4 MUM-BN-02 Te1/0/3 10.251.1.8/31 MUM-CP-02 Te1/0/2 10.251.1.9/31 10G
5 MUM-CP-01 Te1/0/3 10.251.1.10/31 MUM-CP-02 Te1/0/3 10.251.1.11/31 10G
6 MUM-CP-01 Te1/0/4 10.251.1.12/31 MUM-ED-01 Te1/1/1 10.251.1.13/31 10G
7 MUM-CP-02 Te1/0/4 10.251.1.14/31 MUM-ED-01 Te1/½ 10.251.1.15/31 10G
8 MUM-CP-01 Te1/0/5 10.251.1.16/31 MUM-ED-02 Te1/1/1 10.251.1.17/31 10G
9 MUM-CP-02 Te1/0/5 10.251.1.18/31 MUM-ED-02 Te1/½ 10.251.1.19/31 10G
10 MUM-CP-01 Te1/0/6 10.251.1.20/31 MUM-ED-03 Te1/1/1 10.251.1.21/31 10G
11 MUM-CP-02 Te1/0/6 10.251.1.22/31 MUM-ED-03 Te1/½ 10.251.1.23/31 10G
12 MUM-CP-01 Te1/0/7 10.251.1.24/31 MUM-ED-04 Te1/1/1 10.251.1.25/31 10G
13 MUM-CP-02 Te1/0/7 10.251.1.26/31 MUM-ED-04 Te1/½ 10.251.1.27/31 10G
14 MUM-CP-01 Te1/0/8 10.251.1.28/31 MUM-ED-05 Te1/1/1 10.251.1.29/31 10G
15 MUM-CP-02 Te1/0/8 10.251.1.30/31 MUM-ED-05 Te1/½ 10.251.1.31/31 10G
... ... ... ... ... ... ... ...
Link ID From Device From Interface From IP To Device To Interface To IP Speed
0 LON-BN-01 Te1/0/1 10.251.16.0/31 LON-BN-02 Te1/0/1 10.251.16.1/31 10G
1 LON-BN-01 Te1/0/2 10.251.16.2/31 LON-CP-01 Te1/0/1 10.251.16.3/31 10G
2 LON-BN-01 Te1/0/3 10.251.16.4/31 LON-CP-02 Te1/0/1 10.251.16.5/31 10G
3 LON-BN-02 Te1/0/2 10.251.16.6/31 LON-CP-01 Te1/0/2 10.251.16.7/31 10G
4 LON-BN-02 Te1/0/3 10.251.16.8/31 LON-CP-02 Te1/0/2 10.251.16.9/31 10G
5 LON-CP-01 Te1/0/3 10.251.16.10/31 LON-CP-02 Te1/0/3 10.251.16.11/31 10G
6 LON-CP-01 Te1/0/4 10.251.16.12/31 LON-ED-01 Te1/1/1 10.251.16.13/31 10G
7 LON-CP-02 Te1/0/4 10.251.16.14/31 LON-ED-01 Te1/½ 10.251.16.15/31 10G
... ... ... ... ... ... ... ...
Link ID From Device From Interface From IP To Device To Interface To IP Speed
0 NJ-BN-01 Te1/0/1 10.251.32.0/31 NJ-BN-02 Te1/0/1 10.251.32.1/31 10G
1 NJ-BN-01 Te1/0/2 10.251.32.2/31 NJ-CP-01 Te1/0/1 10.251.32.3/31 10G
2 NJ-BN-01 Te1/0/3 10.251.32.4/31 NJ-CP-02 Te1/0/1 10.251.32.5/31 10G
3 NJ-BN-02 Te1/0/2 10.251.32.6/31 NJ-CP-01 Te1/0/2 10.251.32.7/31 10G
4 NJ-BN-02 Te1/0/3 10.251.32.8/31 NJ-CP-02 Te1/0/2 10.251.32.9/31 10G
5 NJ-CP-01 Te1/0/3 10.251.32.10/31 NJ-CP-02 Te1/0/3 10.251.32.11/31 10G
... ... ... ... ... ... ... ...
Link ID From Device From Interface From IP To Device To Interface To IP Speed
0 BLR-FIAB-01 Te1/1/1 10.251.3.0/31 BLR-FIAB-02 Te1/1/1 10.251.3.1/31 10G
1 BLR-FIAB-01 Te1/⅓ 10.251.3.2/31 BLR-ED-01 Te1/1/1 10.251.3.3/31 10G
2 BLR-FIAB-02 Te1/⅓ 10.251.3.4/31 BLR-ED-01 Te1/½ 10.251.3.5/31 10G
3 BLR-FIAB-01 Te1/¼ 10.251.3.6/31 BLR-ED-02 Te1/1/1 10.251.3.7/31 10G
4 BLR-FIAB-02 Te1/¼ 10.251.3.8/31 BLR-ED-02 Te1/½ 10.251.3.9/31 10G
... ... ... ... ... ... ... ...

4.5.4 Management Network Addressing (10.252.0.0/16)

Management Network Design

┌─────────────────────────────────────────────────────────────────────────────┐
│                      MANAGEMENT NETWORK DESIGN                              │
├─────────────────────────────────────────────────────────────────────────────┤
│                                                                             │
│  OUT-OF-BAND MANAGEMENT:                                                    │
│  ───────────────────────                                                    │
│  • Dedicated management VLAN (VLAN 999)                                    │
│  • Separate physical/logical path from production                          │
│  • Jump servers for secure access                                          │
│  • TACACS+ authentication via ISE                                          │
│                                                                             │
│  MANAGEMENT SERVICES:                                                       │
│  ────────────────────                                                       │
│  • DNAC Cluster: 10.252.10.0/24                                            │
│  • ISE Cluster: 10.252.30.0/24                                             │
│  • WLC Management: 10.252.40.0/24                                          │
│  • Network Devices: 10.252.{site}.0/24                                     │
│                                                                             │
└─────────────────────────────────────────────────────────────────────────────┘

Management IP Allocation by Site

Site VLAN Subnet Gateway DHCP Range Reserved
Infrastructure
DNAC Cluster 10 10.252.10.0/24 10.252.10.1 N/A .10-.15 (nodes)
ISE PAN 30 10.252.30.0/24 10.252.30.1 N/A .10-.15 (PAN)
ISE PSN 31 10.252.31.0/24 10.252.31.1 N/A .10-.50 (PSN)
WLC 40 10.252.40.0/24 10.252.40.1 N/A .10-.30 (WLC)
Hub Sites
Mumbai 100 10.252.100.0/24 10.252.100.1 .100-.200 .1-.99
Chennai 101 10.252.101.0/24 10.252.101.1 .100-.200 .1-.99
London 116 10.252.116.0/24 10.252.116.1 .100-.200 .1-.99
Frankfurt 117 10.252.117.0/24 10.252.117.1 .100-.200 .1-.99
New Jersey 132 10.252.132.0/24 10.252.132.1 .100-.200 .1-.99
Dallas 133 10.252.133.0/24 10.252.133.1 .100-.200 .1-.99
Branch Sites
Bangalore 103 10.252.103.0/24 10.252.103.1 .50-.100 .1-.49
Delhi 104 10.252.104.0/24 10.252.104.1 .50-.100 .1-.49
Noida 105 10.252.105.0/24 10.252.105.1 .50-.100 .1-.49

Device Management IP Assignments - All Hub Sites

Mumbai (Site 100)

Hostname Role Management IP Management VLAN
MUM-BN-01 Border Node 10.252.100.11 100
MUM-BN-02 Border Node 10.252.100.12 100
MUM-CP-01 Control Plane 10.252.100.13 100
MUM-CP-02 Control Plane 10.252.100.14 100
MUM-ED-01 Edge Node 10.252.100.21 100
MUM-ED-02 Edge Node 10.252.100.22 100
MUM-ED-03 Edge Node 10.252.100.23 100
MUM-ED-04 Edge Node 10.252.100.24 100
... ... ... ...
MUM-ED-48 Edge Node 10.252.100.68 100
MUM-WLC-01 WLC 10.252.40.11 40
MUM-WLC-02 WLC 10.252.40.12 40

Chennai (Site 101)

Hostname Role Management IP Management VLAN
CHN-BN-01 Border Node 10.252.101.11 101
CHN-BN-02 Border Node 10.252.101.12 101
CHN-CP-01 Control Plane 10.252.101.13 101
CHN-CP-02 Control Plane 10.252.101.14 101
CHN-ED-01 Edge Node 10.252.101.21 101
... ... ... ...

London (Site 116)

Hostname Role Management IP Management VLAN
LON-BN-01 Border Node 10.252.116.11 116
LON-BN-02 Border Node 10.252.116.12 116
LON-CP-01 Control Plane 10.252.116.13 116
LON-CP-02 Control Plane 10.252.116.14 116
LON-ED-01 Edge Node 10.252.116.21 116
... ... ... ...

New Jersey (Site 132)

Hostname Role Management IP Management VLAN
NJ-BN-01 Border Node 10.252.132.11 132
NJ-BN-02 Border Node 10.252.132.12 132
NJ-CP-01 Control Plane 10.252.132.13 132
NJ-CP-02 Control Plane 10.252.132.14 132
NJ-ED-01 Edge Node 10.252.132.21 132
... ... ... ...

4.5.5 IS-IS Configuration

IS-IS NET Address Scheme

NET Format: 49.{area}.{system-id}.00

  • Area ID: 0001 (single area for simplicity)
  • System ID: Derived from Loopback IP (e.g., 10.250.1.1 → 0102.5000.1001)

System ID Derivation:

IP Address: 10.250.1.1
Padded:     010.250.001.001
System ID:  0102.5000.1001
Full NET:   49.0001.0102.5000.1001.00

Complete IS-IS NET Assignments - All Sites

Mumbai

Device Loopback System ID NET
MUM-BN-01 10.250.1.1 0102.5000.1001 49.0001.0102.5000.1001.00
MUM-BN-02 10.250.1.2 0102.5000.1002 49.0001.0102.5000.1002.00
MUM-CP-01 10.250.1.3 0102.5000.1003 49.0001.0102.5000.1003.00
MUM-CP-02 10.250.1.4 0102.5000.1004 49.0001.0102.5000.1004.00
MUM-ED-01 10.250.1.5 0102.5000.1005 49.0001.0102.5000.1005.00
MUM-ED-02 10.250.1.6 0102.5000.1006 49.0001.0102.5000.1006.00

Chennai

Device Loopback System ID NET
CHN-BN-01 10.250.2.1 0102.5000.2001 49.0001.0102.5000.2001.00
CHN-BN-02 10.250.2.2 0102.5000.2002 49.0001.0102.5000.2002.00
CHN-CP-01 10.250.2.3 0102.5000.2003 49.0001.0102.5000.2003.00
CHN-CP-02 10.250.2.4 0102.5000.2004 49.0001.0102.5000.2004.00

London

Device Loopback System ID NET
LON-BN-01 10.250.16.1 0102.5001.6001 49.0001.0102.5001.6001.00
LON-BN-02 10.250.16.2 0102.5001.6002 49.0001.0102.5001.6002.00
LON-CP-01 10.250.16.3 0102.5001.6003 49.0001.0102.5001.6003.00
LON-CP-02 10.250.16.4 0102.5001.6004 49.0001.0102.5001.6004.00

New Jersey

Device Loopback System ID NET
NJ-BN-01 10.250.32.1 0102.5003.2001 49.0001.0102.5003.2001.00
NJ-BN-02 10.250.32.2 0102.5003.2002 49.0001.0102.5003.2002.00
NJ-CP-01 10.250.32.3 0102.5003.2003 49.0001.0102.5003.2003.00
NJ-CP-02 10.250.32.4 0102.5003.2004 49.0001.0102.5003.2004.00

Bangalore (Branch)

Device Loopback System ID NET
BLR-FIAB-01 10.250.3.1 0102.5000.3001 49.0001.0102.5000.3001.00
BLR-FIAB-02 10.250.3.2 0102.5000.3002 49.0001.0102.5000.3002.00
BLR-ED-01 10.250.3.3 0102.5000.3003 49.0001.0102.5000.3003.00

4.5.6 Complete Node Configurations

Global Configuration Template (All Nodes)

! ============================================================================
! GLOBAL CONFIGURATION - ALL FABRIC NODES
! ============================================================================

! Hostname (set per device)
hostname {SITE}-{ROLE}-{NUMBER}

! Enable secret
enable secret 9 $9$xxxx

! Service configuration
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
service sequence-numbers
no service pad
no service config

! Logging configuration
logging buffered 65536 informational
logging console critical
logging monitor warnings
logging trap informational
logging source-interface Loopback0
logging host 10.252.10.30 transport udp port 514

! NTP configuration
ntp server 10.252.10.20 prefer
ntp server 10.252.10.21
ntp source Loopback0

! DNS configuration
ip domain-name corp.local
ip name-server 10.252.10.25
ip name-server 10.252.10.26

! AAA configuration
aaa new-model
aaa authentication login default group tacacs+ local
aaa authentication enable default group tacacs+ enable
aaa authorization console
aaa authorization exec default group tacacs+ local if-authenticated
aaa authorization commands 15 default group tacacs+ local if-authenticated
aaa accounting exec default start-stop group tacacs+
aaa accounting commands 15 default start-stop group tacacs+

tacacs server ISE-TACACS-1
 address ipv4 10.252.30.10
 key 7 xxxxxx
 timeout 5
tacacs server ISE-TACACS-2
 address ipv4 10.252.30.11
 key 7 xxxxxx
 timeout 5

aaa group server tacacs+ ISE-TACACS
 server name ISE-TACACS-1
 server name ISE-TACACS-2

! SNMP configuration
snmp-server community {ro-community} RO
snmp-server community {rw-community} RW
snmp-server location {SITE} - {BUILDING}
snmp-server contact network-operations@corp.local
snmp-server enable traps
snmp-server host 10.252.10.30 version 2c {ro-community}

! VTY configuration
line vty 0 15
 access-class VTY-ACCESS in
 exec-timeout 30 0
 logging synchronous
 transport input ssh
 transport output none

! Console configuration
line con 0
 exec-timeout 15 0
 logging synchronous
 stopbits 1

! SSH configuration
ip ssh version 2
ip ssh time-out 60
ip ssh authentication-retries 3
crypto key generate rsa modulus 4096

! Archive configuration
archive
 path flash:archive
 write-memory

! Access lists
ip access-list standard VTY-ACCESS
 permit 10.252.0.0 0.0.255.255
 permit 10.250.0.0 0.0.255.255
 deny any log

! Banner
banner login ^
*************************************************************
*                    AUTHORIZED ACCESS ONLY                  *
*  Unauthorized access to this device is prohibited.         *
*  All activities are logged and monitored.                  *
*************************************************************
^

! ============================================================================
! MTU CONFIGURATION - CRITICAL FOR VXLAN
! ============================================================================
system mtu 9100

Border Node Complete Configuration

! ============================================================================
! BORDER NODE CONFIGURATION
! Example: MUM-BN-01 (C9500-48Y4C)
! ============================================================================

hostname MUM-BN-01

! --- Loopback Interface (RLOC) ---
interface Loopback0
 description FABRIC-RLOC-BORDER
 ip address 10.250.1.1 255.255.255.255
 ip router isis UNDERLAY
 isis circuit-type level-2-only

! --- IS-IS Process Configuration ---
router isis UNDERLAY
 net 49.0001.0102.5000.1001.00
 is-type level-2-only
 metric-style wide
 log-adjacency-changes all
 nsf ietf
 authentication mode md5 level-2
 authentication key-chain ISIS-KEY level-2
 passive-interface Loopback0
 !
 address-family ipv4 unicast
  redistribute connected route-map LOOPBACK-REDISTRIBUTE
 exit-address-family

! --- IS-IS Authentication Key Chain ---
key chain ISIS-KEY
 key 1
  key-string 7 {encrypted-key}
  cryptographic-algorithm hmac-sha-256
  send-lifetime 00:00:00 Jan 1 2025 infinite
  accept-lifetime 00:00:00 Jan 1 2025 infinite

! --- Route Map for Loopback Redistribution ---
route-map LOOPBACK-REDISTRIBUTE permit 10
 match interface Loopback0
!
route-map LOOPBACK-REDISTRIBUTE deny 20

! --- P2P Link to Border-2 ---
interface TenGigabitEthernet1/0/1
 description P2P-TO-MUM-BN-02
 no switchport
 mtu 9100
 ip address 10.251.1.0 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- P2P Link to CP-1 ---
interface TenGigabitEthernet1/0/2
 description P2P-TO-MUM-CP-01
 no switchport
 mtu 9100
 ip address 10.251.1.2 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- P2P Link to CP-2 ---
interface TenGigabitEthernet1/0/3
 description P2P-TO-MUM-CP-02
 no switchport
 mtu 9100
 ip address 10.251.1.4 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- Management Interface ---
interface Vlan999
 description MANAGEMENT
 ip address 10.252.100.11 255.255.255.0
 no shutdown

interface TenGigabitEthernet1/0/47
 description MGMT-UPLINK
 switchport access vlan 999
 switchport mode access
 spanning-tree portfast

! --- QoS for Underlay ---
class-map match-any UNDERLAY-CONTROL
 match protocol isis
 match protocol bfd

policy-map UNDERLAY-EGRESS
 class UNDERLAY-CONTROL
  set dscp cs6
 class class-default
  set dscp default

interface range TenGigabitEthernet1/0/1-3
 service-policy output UNDERLAY-EGRESS

! --- BFD Global Configuration ---
bfd slow-timers 12000

! --- IP Routing ---
ip routing
ip multicast-routing

! --- Static Routes for Management ---
ip route 0.0.0.0 0.0.0.0 10.252.100.1 name MGMT-DEFAULT

! --- Save Configuration ---
end
write memory

Control Plane Node Complete Configuration

! ============================================================================
! CONTROL PLANE NODE CONFIGURATION
! Example: MUM-CP-01 (C9500-24Y4C)
! ============================================================================

hostname MUM-CP-01

! --- Loopback Interface (RLOC) ---
interface Loopback0
 description FABRIC-RLOC-CP
 ip address 10.250.1.3 255.255.255.255
 ip router isis UNDERLAY
 isis circuit-type level-2-only

! --- IS-IS Process Configuration ---
router isis UNDERLAY
 net 49.0001.0102.5000.1003.00
 is-type level-2-only
 metric-style wide
 log-adjacency-changes all
 nsf ietf
 authentication mode md5 level-2
 authentication key-chain ISIS-KEY level-2
 passive-interface Loopback0
 !
 address-family ipv4 unicast
  redistribute connected route-map LOOPBACK-REDISTRIBUTE
 exit-address-family

! --- IS-IS Authentication Key Chain ---
key chain ISIS-KEY
 key 1
  key-string 7 {encrypted-key}
  cryptographic-algorithm hmac-sha-256

! --- Route Map for Loopback Redistribution ---
route-map LOOPBACK-REDISTRIBUTE permit 10
 match interface Loopback0

! --- P2P Link to Border-1 ---
interface TenGigabitEthernet1/0/1
 description P2P-TO-MUM-BN-01
 no switchport
 mtu 9100
 ip address 10.251.1.3 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- P2P Link to Border-2 ---
interface TenGigabitEthernet1/0/2
 description P2P-TO-MUM-BN-02
 no switchport
 mtu 9100
 ip address 10.251.1.7 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- P2P Link to CP-2 ---
interface TenGigabitEthernet1/0/3
 description P2P-TO-MUM-CP-02
 no switchport
 mtu 9100
 ip address 10.251.1.10 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- P2P Links to Edge Nodes ---
interface TenGigabitEthernet1/0/4
 description P2P-TO-MUM-ED-01
 no switchport
 mtu 9100
 ip address 10.251.1.12 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

interface TenGigabitEthernet1/0/5
 description P2P-TO-MUM-ED-02
 no switchport
 mtu 9100
 ip address 10.251.1.16 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

interface TenGigabitEthernet1/0/6
 description P2P-TO-MUM-ED-03
 no switchport
 mtu 9100
 ip address 10.251.1.20 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! Continue for all edge nodes...

! --- Management Interface ---
interface Vlan999
 description MANAGEMENT
 ip address 10.252.100.13 255.255.255.0
 no shutdown

! --- IP Routing ---
ip routing

! --- Static Routes for Management ---
ip route 0.0.0.0 0.0.0.0 10.252.100.1 name MGMT-DEFAULT

Edge Node Complete Configuration

! ============================================================================
! EDGE NODE CONFIGURATION
! Example: MUM-ED-01 (C9300-48UXM)
! ============================================================================

hostname MUM-ED-01

! --- Loopback Interface (RLOC) ---
interface Loopback0
 description FABRIC-RLOC-EDGE
 ip address 10.250.1.5 255.255.255.255
 ip router isis UNDERLAY
 isis circuit-type level-2-only

! --- IS-IS Process Configuration ---
router isis UNDERLAY
 net 49.0001.0102.5000.1005.00
 is-type level-2-only
 metric-style wide
 log-adjacency-changes all
 nsf ietf
 authentication mode md5 level-2
 authentication key-chain ISIS-KEY level-2
 passive-interface Loopback0
 !
 address-family ipv4 unicast
  redistribute connected route-map LOOPBACK-REDISTRIBUTE
 exit-address-family

! --- IS-IS Authentication Key Chain ---
key chain ISIS-KEY
 key 1
  key-string 7 {encrypted-key}
  cryptographic-algorithm hmac-sha-256

! --- Uplink to CP-1 (10G SFP+) ---
interface TenGigabitEthernet1/1/1
 description UPLINK-TO-MUM-CP-01
 no switchport
 mtu 9100
 ip address 10.251.1.13 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- Uplink to CP-2 (10G SFP+) ---
interface TenGigabitEthernet1/1/2
 description UPLINK-TO-MUM-CP-02
 no switchport
 mtu 9100
 ip address 10.251.1.15 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- Management Interface ---
interface Vlan999
 description MANAGEMENT
 ip address 10.252.100.21 255.255.255.0
 no shutdown

interface GigabitEthernet1/0/48
 description MGMT-UPLINK
 switchport access vlan 999
 switchport mode access
 spanning-tree portfast

! --- Host-Facing Ports (Pre-configuration) ---
! These will be configured by DNAC for 802.1X/MAB
interface range GigabitEthernet1/0/1-44
 description USER-ACCESS-PORT
 switchport mode access
 switchport access vlan 1
 spanning-tree portfast
 spanning-tree bpduguard enable
 shutdown

! --- AP Ports ---
interface range GigabitEthernet1/0/45-47
 description AP-PORT
 switchport mode trunk
 spanning-tree portfast trunk
 shutdown

! --- IP Routing ---
ip routing

! --- Static Routes for Management ---
ip route 0.0.0.0 0.0.0.0 10.252.100.1 name MGMT-DEFAULT

Branch Fabric-in-a-Box Configuration

! ============================================================================
! FABRIC-IN-A-BOX CONFIGURATION
! Example: BLR-FIAB-01 (C9300-48UXM)
! ============================================================================

hostname BLR-FIAB-01

! --- Loopback Interface (RLOC) ---
interface Loopback0
 description FABRIC-RLOC-FIAB
 ip address 10.250.3.1 255.255.255.255
 ip router isis UNDERLAY
 isis circuit-type level-2-only

! --- IS-IS Process Configuration ---
router isis UNDERLAY
 net 49.0001.0102.5000.3001.00
 is-type level-2-only
 metric-style wide
 log-adjacency-changes all
 nsf ietf
 authentication mode md5 level-2
 authentication key-chain ISIS-KEY level-2
 passive-interface Loopback0
 !
 address-family ipv4 unicast
  redistribute connected route-map LOOPBACK-REDISTRIBUTE
 exit-address-family

! --- StackWise Virtual Link to FiaB-2 ---
interface TenGigabitEthernet1/1/1
 description SVL-TO-BLR-FIAB-02
 no switchport
 mtu 9100
 ip address 10.251.3.0 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- Downlinks to Edge Nodes ---
interface TenGigabitEthernet1/1/3
 description DOWNLINK-TO-BLR-ED-01
 no switchport
 mtu 9100
 ip address 10.251.3.4 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

interface TenGigabitEthernet1/1/4
 description DOWNLINK-TO-BLR-ED-02
 no switchport
 mtu 9100
 ip address 10.251.3.6 255.255.255.254
 ip router isis UNDERLAY
 isis circuit-type level-2-only
 isis network point-to-point
 isis authentication mode md5
 isis authentication key-chain ISIS-KEY
 bfd interval 100 min_rx 100 multiplier 3
 no shutdown

! --- SD-WAN Handoff Interface ---
interface TenGigabitEthernet1/1/8
 description TO-BLR-SDWAN-01
 switchport mode trunk
 switchport trunk allowed vlan 3001-3005
 no shutdown

! --- Management Interface ---
interface Vlan999
 description MANAGEMENT
 ip address 10.252.103.11 255.255.255.0
 no shutdown

! --- IP Routing ---
ip routing

! --- Default Route via SD-WAN ---
ip route 0.0.0.0 0.0.0.0 10.252.103.1 name MGMT-DEFAULT

4.5.7 Pre-Provisioning Checklist

Physical Layer Verification

Check Command/Action Expected Result
Cable labeling Visual inspection All cables labeled per standard
Cable certification Cat6a/OM4 test report Pass for all fabric links
SFP+ compatibility show inventory Cisco-branded or validated
Port LED status Visual inspection Link lights on for connected ports
Power redundancy show environment power Dual PSU, both OK
Rack elevation Documentation review Matches rack diagram

Pre-Staging Verification

# Device Pre-Staging Checklist Script
# Run on each device before fabric provisioning

echo "=== PRE-STAGING VERIFICATION ==="

echo "1. Software Version Check"
show version | include Software

echo "2. Hardware Inventory"
show inventory

echo "3. Memory Status"
show processes memory sorted | head 10

echo "4. Flash Space"
show flash:

echo "5. Management Connectivity"
ping 10.252.10.10    ! DNAC
ping 10.252.30.10    ! ISE

echo "6. NTP Status"
show ntp status

echo "7. AAA Status"
test aaa group tacacs+ admin {password} legacy

echo "8. Interface Status"
show ip interface brief

echo "9. Neighbor Discovery"
show cdp neighbors

echo "10. Pre-existing Config (should be minimal)"
show running-config | include ^interface|^router|^vlan

4.5.8 Comprehensive Underlay Validation

IS-IS Validation Commands

! ============================================================================
! IS-IS VALIDATION SUITE
! ============================================================================

! --- Verify IS-IS Process ---
show isis neighbors
! Expected: All connected neighbors UP, L2 adjacency

! Example output:
! System Id      Type Interface         IP Address      State Holdtime Circuit Id
! MUM-BN-02      L2   Te1/0/1           10.251.1.1      UP    27       MUM-BN-01.01
! MUM-CP-01      L2   Te1/0/2           10.251.1.3      UP    28       MUM-BN-01.02
! MUM-CP-02      L2   Te1/0/3           10.251.1.5      UP    26       MUM-BN-01.03

! --- Verify IS-IS Database ---
show isis database detail
! Expected: All fabric nodes present in database

! --- Verify IS-IS Routes ---
show ip route isis
! Expected: All loopback /32 routes present

! Example output:
! i L2     10.250.1.2/32 [115/20] via 10.251.1.1, Te1/0/1
! i L2     10.250.1.3/32 [115/20] via 10.251.1.3, Te1/0/2
! i L2     10.250.1.4/32 [115/20] via 10.251.1.5, Te1/0/3
! i L2     10.250.1.5/32 [115/30] via 10.251.1.3, Te1/0/2

! --- Verify Metrics ---
show isis rib
! Check for consistent metrics

! --- Verify Authentication ---
show isis neighbors detail | include Auth
! Expected: Authentication successful on all adjacencies

BFD Validation Commands

! ============================================================================
! BFD VALIDATION SUITE
! ============================================================================

! --- Verify BFD Sessions ---
show bfd neighbors
! Expected: All sessions UP

! Example output:
! IPv4 Sessions
! NeighAddr           LD/RD   RH/RS   State     Int
! 10.251.1.1          1/1     Up      Up        Te1/0/1
! 10.251.1.3          2/2     Up      Up        Te1/0/2
! 10.251.1.5          3/3     Up      Up        Te1/0/3

! --- Verify BFD Details ---
show bfd neighbors detail
! Check interval, multiplier, echo mode

! --- Verify BFD Statistics ---
show bfd neighbors counters
! Check for any packet drops

Connectivity Validation Scripts

! ============================================================================
! CONNECTIVITY VALIDATION - RUN FROM EACH NODE
! ============================================================================

! --- Loopback Ping Test (Mumbai) ---
! From MUM-BN-01:
ping 10.250.1.2 source 10.250.1.1    ! BN-02
ping 10.250.1.3 source 10.250.1.1    ! CP-01
ping 10.250.1.4 source 10.250.1.1    ! CP-02
ping 10.250.1.5 source 10.250.1.1    ! ED-01
ping 10.250.1.6 source 10.250.1.1    ! ED-02
! ... continue for all nodes

! --- MTU Verification (CRITICAL) ---
! Test with large packets to ensure VXLAN will work
ping 10.250.1.2 source 10.250.1.1 size 8972 df-bit
! Expected: Success (8972 + 28 IP/ICMP = 9000 < 9100 MTU)

ping 10.250.1.2 source 10.250.1.1 size 9072 df-bit
! Expected: Fail if MTU is exactly 9100

! --- Traceroute Verification ---
traceroute 10.250.1.5 source 10.250.1.1
! Verify expected path through fabric

! --- End-to-End Latency ---
ping 10.250.1.5 source 10.250.1.1 repeat 1000
! Check for <1ms latency within site

4.5.9 Troubleshooting Common Issues

Issue 1: IS-IS Adjacency Not Forming

! Diagnostic commands
show isis neighbors
show isis interface
show isis adjacency-log
debug isis adj-packets

! Common causes and fixes:
! 1. MTU mismatch - Verify MTU on both ends
show interface Te1/0/1 | include MTU

! 2. Authentication mismatch
show isis neighbors detail | include Auth
show key chain

! 3. Level mismatch (should be L2-only)
show running-config | include isis.*level

! 4. Network type mismatch
show running-config interface Te1/0/1 | include network

Issue 2: BFD Session Flapping

! Diagnostic commands
show bfd neighbors detail
show bfd neighbors counters
show logging | include BFD

! Common causes and fixes:
! 1. Aggressive timers with CPU issues
show processes cpu history
! Consider relaxing BFD timers if CPU is high

! 2. Optical/cable issues
show interface Te1/0/1 | include errors|CRC

! 3. Micro-bursts causing drops
show interface Te1/0/1 | include output drops

Issue 3: Incomplete Route Table

! Diagnostic commands
show ip route isis
show isis database detail
show isis topology

! Common causes and fixes:
! 1. Route redistribution not configured
show running-config | include redistribute

! 2. Prefix filtering
show running-config | include route-map|prefix-list

! 3. Network partitioned
show isis neighbors
show isis database | include Number

4.5.10 Summary and Sign-Off

Underlay Provisioning Checklist

Phase Task Completed Verified By Date
Pre-Staging
Cable installation complete
All devices racked and powered
Base IOS installed
Management IP configured
AAA/NTP/DNS configured
IS-IS Configuration
Loopbacks configured
IS-IS process configured
P2P links configured
Authentication enabled
BFD enabled
Validation
All IS-IS adjacencies UP
All BFD sessions UP
Full loopback reachability
MTU test passed (9000+ bytes)
Convergence test passed (<2s)
Documentation
IP allocation spreadsheet updated
Topology diagrams updated
Configuration backed up

Approval Sign-Off

Role Name Signature Date
Network Engineer
Network Architect
Project Manager