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Topology planning in MCP Packet Tracer is the process of translating a plain-English prompt — such as “create a network with 3 routers, OSPF, and DHCP” — into a fully validated TopologyPlan object containing every device, cable, IP address, DHCP pool, routing config, and expansion module required to deploy the network. The planning engine handles subnet allocation, cable inference, port assignment, and protocol configuration automatically, so neither the LLM nor the user needs to think about any of those details.

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How Planning Works

Every topology starts as a TopologyRequest and ends as a TopologyPlan. The orchestrator pipeline looks like this: 
TopologyRequest
      │
  Orchestrator ─── IPPlanner (assigns /24 LANs + /30 inter-router WAN links)
      │
  Validator    ─── 24 typed error codes, port/cable/IP checks
      │
  AutoFixer    ─── fixes wrong cables, upgrades routers, reassigns ports
      │
  TopologyPlan (validated, fully addressed)
The TopologyPlan that comes back contains:
  • Devices — model, category, canvas coordinates, and role for every node
  • Links — inferred or explicit cable types between every pair of devices
  • IP addressing — fully assigned interface IPs on every router, PC, and server
  • DHCP pools — one pool per LAN with gateway excluded
  • Static routes / OSPF / EIGRP / RIP config — complete IOS command blocks per router
  • Expansion modules — HWIC-2T or NIM-2T entries when serial links are needed

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Topology Templates

Templates are hints that guide the orchestrator’s topology-building logic. Each template sets sensible defaults for router count, PC distribution, switches, and routing protocol.
TemplateDescriptionDefault Routing
single_lan1 router + 1 switch + N PCs — simplest local networkstatic
multi_lanN routers in a chain, each with their own LANstatic
multi_lan_wanMulti-LAN topology with a WAN Cloud node attachedstatic
star1 central router connected to N switches (hub-and-spoke variant)static
hub_spoke1 hub router + N spoke routers, each spoke with its own LANstatic
branch_officeHeadquarters + branch sites connected through a WAN cloudstatic
router_on_a_stick1 router + 1 switch for inter-VLAN routing via subinterfacesstatic
three_router_triangle3 routers in a triangle with route redundancyospf
customFree-form — all parameters are set manually, no enforced structurenone
Template selection is a hint, not a hard constraint. You can override any default by specifying fields explicitly in the request — for example, setting routing: "ospf" on a single_lan template.

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pt_full_build vs pt_plan_topology

Both tools plan a topology, but they serve different purposes.

pt_full_build

All-in-one pipeline: plan + validate + fix + generate + explain in a single call. Returns a human-readable report describing every decision. Best for interactive prompts where you want an immediate overview.

pt_plan_topology

Returns machine-readable JSON (TopologyPlan). Use this when you need the plan as structured input for downstream tools like pt_generate_script, pt_generate_configs, or pt_export.
pt_full_build is not intended as JSON input for other tools — its output is a narrative report with the JSON embedded at the end for reference only. For programmatic pipelines, always use pt_plan_topology.

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Using pt_plan_topology

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Example Request

pt_plan_topology accepts individual named parameters — not a JSON string. Pass each option directly. The tool picks sensible defaults for anything you omit. 
pt_plan_topology(
    routers=2,
    pcs_per_lan=2,
    template="multi_lan",
    routing="static",
    dhcp=True
)

​
Example Response (excerpt)

{
  "devices": [
    { "name": "R1", "model": "2911", "category": "router", "x": 100, "y": 100,
      "interfaces": { "GigabitEthernet0/0": "192.168.0.1/24", "GigabitEthernet0/1": "10.0.0.1/30" } },
    { "name": "R2", "model": "2911", "category": "router", "x": 350, "y": 100,
      "interfaces": { "GigabitEthernet0/0": "192.168.1.1/24", "GigabitEthernet0/1": "10.0.0.2/30" } },
    { "name": "SW1", "model": "2960-24TT", "category": "switch", "x": 100, "y": 250 },
    { "name": "SW2", "model": "2960-24TT", "category": "switch", "x": 350, "y": 250 },
    { "name": "PC1", "model": "PC-PT", "category": "pc",
      "interfaces": { "FastEthernet0": "192.168.0.2/24" }, "gateway": "192.168.0.1" },
    { "name": "PC2", "model": "PC-PT", "category": "pc",
      "interfaces": { "FastEthernet0": "192.168.0.3/24" }, "gateway": "192.168.0.1" }
  ],
  "links": [
    { "device_a": "R1", "port_a": "GigabitEthernet0/1", "device_b": "R2", "port_b": "GigabitEthernet0/1", "cable": "cross" },
    { "device_a": "R1", "port_a": "GigabitEthernet0/0", "device_b": "SW1", "port_b": "GigabitEthernet0/1", "cable": "straight" }
  ],
  "dhcp_pools": [
    { "router": "R1", "pool_name": "LAN_R1_0", "network": "192.168.0.0", "mask": "255.255.255.0",
      "gateway": "192.168.0.1", "dns": "8.8.8.8" }
  ],
  "static_routes": [
    { "router": "R1", "destination": "192.168.1.0", "mask": "255.255.255.0", "next_hop": "10.0.0.2" },
    { "router": "R2", "destination": "192.168.0.0", "mask": "255.255.255.0", "next_hop": "10.0.0.1" }
  ],
  "is_valid": true
}

​
Prompt Tips

Say “3 routers, 2 PCs per LAN” rather than “a few routers with some PCs.” The planner uses explicit numbers to determine subnet count, port allocation, and route generation.
Include “OSPF,” “EIGRP,” “RIP,” or “static routing” in your prompt. Without it, the planner defaults to static for most templates. For redundant topologies, say “OSPF with floating static backup routes.”
DHCP pool generation is on by default, but stating “with DHCP” makes the intent clear and avoids the LLM accidentally passing dhcp: false.
Saying “hub-and-spoke topology” will pick the hub_spoke template with 4 routers by default. Add routing="eigrp" to get EIGRP — a popular choice for hub-and-spoke labs.

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Next Steps

pt_plan_topology

Full parameter reference for the planning tool

pt_full_build

All-in-one build + explain pipeline

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