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Checking AS configuration

Introduction

After configuring your AS on the SCIONLab website and installing SCION you should now have a running SCIONLab AS. Follow the steps below to check that it is working as expected.

Running Webapp

If you’re running a VM, the simplest and recommended way of verifying a correct SCION infrastructure deployment is running the visualization tool SCIONLab Apps Web Visualization. This browser-based tool serves as a dashboard to your SCIONLab VM and includes various checks.

Terminal based

For the following steps, log into the machine hosting the SCION services (with vagrant ssh if it is a virtual machine). If any of the checks fail, head over to the Troubleshooting Guide

Check VPN tunnel

This only applies if you’ve configured your as to use an OpenVPN connection to the Attachment Point.

Check that the tunnel interface exists:

sudo ip address show dev tun0

Check that /etc/openvpn/client-scionlab-<attachment point ISD-AS>.conf exists.

Check that the OpenVPN client is up:

sudo systemctl status openvpn@client-scionlab-*

Check that the IP address in the topology.json file matches the IP assigned in the VPN: Open any of the topology.json files and search the interfaces entry:

$ grep interfaces -A10 /etc/scion/topology.json
    "interfaces": {
      "1": {
        "isd_as": "17-ffaa:0:1107",
        "underlay": {
          "public": "10.1.0.113:50000"",
          "remote": "10.1.0.1:50168"
        },
        "bandwidth": 1000,
        "link_to": "PARENT",
        "mtu": 1472
      }

In this entry, the public address should correspond to the local address on your tunnel interface.

Check that the VPN tunnel is working, by pinging the address listed in remote.

Check SCION service status

sudo systemctl list-dependencies scionlab.target

This should show all entries as green. If there are any failed services in this list, start troubleshooting

If you’re running a build from sources, you will need to use the developer scripts instead of systemctl. Run scion.sh status or supervisor/supervisor.sh status.

Check the border router interface status

  • Inspect the border router’s log (using sudo journactl -u scion-border-router@br-1.service) to check that the bidirectional-forwarding detection (bfd) handshake completed and the interfaces are “active”:

    Check that the log mentions Transitioned from state ... to state Up, not followed by a later ... to state Down.

  • Alternatively, you can check the same information in metrics of the border router. For the default SCIONLab User AS setup, this is exposed on localhost, port 30401.

    $ curl -sfS localhost:30401/metrics | grep router_interface_up
    # HELP router_interface_up Either zero or one depending on whether the interface is up.
    # TYPE router_interface_up gauge
    router_interface_up{interface="1",isd_as="1-ff00:0:112",neighbor_isd_as="1-ff00:0:110"} 1
    

Check that beacons are registered

An AS needs to receive path construction beacons from it’s upstream provider AS(es) in order to be able to communicate.

  • Inspect the control service’s log (using sudo journalctl -u scion-control-service@cs-1.service) to check that beacons are registered successfully.

    Check that you find entries Registered beacons ..., with "count": 1 (any non-zero count).

  • Alternatively, you can check the same information in metrics of the control service, exposed by default on localhost, port 30454.

    $ curl -sfS localhost:30454/metrics | grep control_beaconing_received_beacons_total
    # HELP control_beaconing_received_beacons_total Total number of beacons received.
    # TYPE control_beaconing_received_beacons_total counter
    control_beaconing_received_beacons_total{ingress_interface="41",neighbor_isd_as="1-ff00:0:110",result="ok_updated"} 38
    

    Note: this returns an empty result if no beacons have been recieved.

Ping

Ping somebody! Run scion ping to send an “SCMP echo request”; this is just like the ping command for IP.

The syntax is:

scion ping [destination SCION address]

where a SCION address has the form ISD-AS,IP. An example of pinging a host in the attachment point AS in Korea would look as follows:

$ scion ping 20-ffaa:0:1404,0.0.0.0
Resolved local address:
  127.0.0.1
Using path:
  Hops: [17-ffaa:1:15b 1>169 17-ffaa:0:1107 1>4 17-ffaa:0:1102 2>2 17-ffaa:0:1103 4>8 17-ffaa:0:1101 11>3 19-ffaa:0:1302 1>7 19-ffaa:0:1301 3>5 18-ffaa:0:1201 3>5 20-ffaa:0:1401 7>1 20-ffaa:0:1403 3>47 20-ffaa:0:1404] MTU: 1472, NextHop: 127.0.0.1:30042

PING 20-ffaa:0:1404,0.0.0.0 pld=0B scion_pkt=192B
200 bytes from 20-ffaa:0:1404,0.0.0.0: scmp_seq=0 time=383.578ms
200 bytes from 20-ffaa:0:1404,0.0.0.0: scmp_seq=1 time=381.763ms

Passing this test is a condition sufficient to say that your AS works as expected. If it fails, please refer to the troubleshooting section.


Copyright © 2020, Network Security Group, ETH Zurich