Topology Graph Output Module

graph output module create a description of network topology in graphviz DOT format. You can use that description with graphviz commands to create topology diagrams in numerous output formats.

Note: The network topology graph description contains nodes and links but no placement information. graphviz is pretty good at figuring out how to draw the required graph, but it pays out to test out various layout engines (hint: use the name of the layout engine as the CLI command).

The graph output module is invoked by specifying -o graph parameter in netlab create command. It takes an optional destination file name (default:

A single formatting modifier can be used to specify the graph type:

  • topology (default) – Include, physical links, and multi-access- and stub subnets. When the network topology contains BGP information, the graph groups nodes into autonomous systems. Alternatively, you could set defaults.outputs.graph.groups attribute to use topology groups to group graph nodes.

  • bgp – Include autonomous systems, nodes, and BGP sessions. With the rr option (specified with netlab create -o graph:bgp:rr), RR-client sessions are drawn as directed arrows.

Modifying Graph Attributes

Graphing routines use default topology settings to modify the node- or link parameters of the generated DOT file:

  • outputs.graph.interface_labels – Add IP addresses to links in topology graph. Results in a cluttered image (but feel free to fix that and submit a pull request).

  • outputs.graph.colors.object – Specify background color for as, node, stub subnet, ibgp or ebgp session.

  • – Inner margin for graph clusters (BGP autonomous system or groups).

  • outputs.graph.groups – use the specified list of groups (or all groups when set to True) to create graph clusters

  • outputs.graphs.node_address_labels – add node loopback IP addresses or IP addresses of the first interface (for hosts) to node labels.

You could specify these attributes in your topology file, in per-user topology defaults, or in system defaults (more details). You could also specify them with -s parameter of netlab create command (more details). The system defaults in netsim-tools release 1.2.4 are included below:

    interface_labels: False
    node_address_label: True
    as_clusters: True
      as: "#e8e8e8"
      node: "#ff9f01"
      stub: "#d1bfab"
      ibgp: "#613913"
      ebgp: "#b21a1a"
      as: 16