CML Topology Builder

Build network topologies in Cisco Modeling Labs from natural language. Add nodes, create interfaces, wire links, set bandwidth/delay/loss conditions, and annotate the topology with visual documentation.

MCP Server

• Command: cml-mcp (pip-installed, stdio transport)
• Requires: CML_URL, CML_USERNAME, CML_PASSWORD environment variables

Available Tools

Node Management

Tool	Parameters	What It Does
get_node_defs	none	List all available node definitions (IOSv, NX-OS, IOS-XR, etc.)
create_node	lab_id/lab_title, node_def, label, x, y	Add a node to a lab
get_nodes	lab_id/lab_title	List all nodes in a lab
get_node	lab_id/lab_title, node_id/node_label	Get details of a specific node

Interface Management

Tool	Parameters	What It Does
create_interface	lab_id/lab_title, node_id/node_label, slot?	Create a new interface on a node
get_interfaces	lab_id/lab_title, node_id/node_label	List all interfaces on a node
get_interface	lab_id/lab_title, node_id/node_label, interface_id/interface_label	Get interface details

Link Management

Tool	Parameters	What It Does
create_link	lab_id/lab_title, src_node/src_label, src_intf, dst_node/dst_label, dst_intf	Create a link between two interfaces
get_links	lab_id/lab_title	List all links in a lab
get_link	lab_id/lab_title, link_id	Get link details
set_link_condition	lab_id/lab_title, link_id, bandwidth?, latency?, jitter?, loss?	Set link conditioning (WAN simulation)
set_link_state	lab_id/lab_title, link_id, state	Set link state (up/down) — simulate link failures

Annotations

Tool	Parameters	What It Does
create_annotation	lab_id/lab_title, annotation_type, content, x, y, width?, height?	Add a text/shape annotation
get_annotations	lab_id/lab_title	List all annotations
delete_annotation	lab_id/lab_title, annotation_id	Remove an annotation

Available Node Definitions

Common node types available in CML (use get_node_defs to get the full list):

Node Definition ID	Description	Typical Use
iosv	Cisco IOSv (IOS 15.x)	Routing, switching labs
iosvl2	Cisco IOSv L2	Layer 2 switching labs
iosxrv9000	Cisco IOS XR 9000v	SP, MPLS, Segment Routing
nxosv9000	Cisco NX-OS 9000v	Data center, VXLAN
csr1000v	Cisco CSR 1000v (IOS-XE)	SD-WAN, routing
cat8000v	Cisco Catalyst 8000v	Enterprise routing
asav	Cisco ASAv	Firewall labs
server	Ubuntu/Alpine server	Traffic gen, testing
external_connector	External bridge	Connect lab to host/internet
unmanaged_switch	Unmanaged L2 switch	Simple L2 connectivity
wan_emulator	WAN emulator	Add latency/loss between nodes

Workflow: Build Topology from Description

When the user describes a topology:

1. Create the lab (or get an existing one via get_lab)
2. Get node definitions: get_node_defs to know what's available
3. Plan the layout: Calculate x,y coordinates for visual placement
   • Use a grid layout: 200px spacing horizontally, 200px vertically
   • Group by role: core in center, edge on sides, servers at bottom
4. Create nodes: create_node for each device with meaningful labels
5. Create interfaces: create_interface for each connection point
6. Wire links: create_link to connect interface pairs
7. Set conditions (if requested): set_link_condition for WAN links
8. Add annotations: create_annotation for labels, IP addressing plans
9. Report the topology: List all nodes, interfaces, and links

Layout Guidelines

When placing nodes, use this visual grid approach:

Topology Layout (x, y coordinates):

Layer 0 (Top):     Core routers         y=100
Layer 1:           Distribution          y=300
Layer 2:           Access / Leaf         y=500
Layer 3 (Bottom):  Servers / Endpoints   y=700

x spacing: 200px between nodes in the same layer
Center the topology: start x at 100, distribute evenly

Example for a 2-spine, 4-leaf topology:

Spine1: (300, 100)    Spine2: (500, 100)
Leaf1:  (100, 300)    Leaf2:  (300, 300)    Leaf3:  (500, 300)    Leaf4:  (700, 300)
Srv1:   (100, 500)    Srv2:   (300, 500)    Srv3:   (500, 500)    Srv4:   (700, 500)

Link Conditioning

Use set_link_condition to simulate real-world WAN characteristics:

Scenario	Bandwidth	Latency	Jitter	Loss
LAN	(none)	(none)	(none)	(none)
Metro Ethernet	100 Mbps	5 ms	1 ms	0%
WAN (good)	50 Mbps	20 ms	5 ms	0.1%
WAN (poor)	10 Mbps	100 ms	20 ms	1%
Satellite	5 Mbps	300 ms	50 ms	2%
Congested link	1 Mbps	200 ms	100 ms	5%

Workflow: Annotate Topology

After building a topology, add visual documentation:

1. Title annotation: Lab name and purpose at the top
2. IP addressing: Annotation blocks showing subnet assignments per link
3. AS numbers: Label BGP AS boundaries
4. Area labels: Mark OSPF areas, VRF names, VLAN IDs
5. Notes: Any special instructions or test scenarios

Workflow: Simulate Link Failure

When testing network resilience:

1. Get the link: get_links to find the link ID between the two nodes
2. Capture baseline: Use execute_command to check routing tables before failure
3. Bring link down: set_link_state with state "down"
4. Observe convergence: Execute show commands on affected nodes (OSPF neighbors, BGP summary, routing table)
5. Optionally capture traffic: Use cml-packet-capture to capture reconvergence traffic
6. Restore link: set_link_state with state "up"
7. Verify recovery: Confirm routing adjacencies re-establish
8. Report: Document failover/failback time and behavior

Important Rules

• Always use get_node_defs first to verify available node types before creating nodes
• Create interfaces before links — you need interface IDs to wire links
• Use descriptive labels — "R1-Core" not "Node1"
• Plan before building — figure out the full topology before starting to create nodes
• Lab must be STOPPED to add nodes — cannot modify topology of a running lab
• Position nodes logically — hierarchical layout makes the topology readable in CML UI
• Record in GAIT — log topology creation for audit trail