Test Network Configuration

Questions

• Is the XO connected to local-link or a mesh?
• Is it connected to an MPP?
• Is it connected to the internet?
• Is it connected to a jabber server?
• What is the ip?

Layer 2

The wireless configuration of the network can be examined using the iwconfig eth0 command. We get MAC layer information such as

1. ESSID
   • olpc-mesh : Indicates a mesh with or without internet connectivity
2. Mode
   • Managed : It is an Access Point(AP) configuration
   • Ad-hoc : It is a mesh configuration(no infrastracture)
3. Frequency
   • 2.412 : Channel 1
   • 2.437 : Channel 6
   • 2.462 : Channel 11
   • Channels 1,6,11 can be used to join a mesh
   • Channel 1 includes a Schoolserver
   • Media lab AP operates on Channels 6 and 11
4. Cell/AP Mac
   • Access Point : The AP's MAC
   • Cell : A virtual 02:xx:xx:... MAC address assigned by the some mesh points. It indicateS mesh configuration

Layer 3

IP addresses

The network layer information can be observed with ifconfig. The eth0 part gives an IPv4 address only if the XO is connected directly to an AP. The address can also indicate a private network. Media lab gives an 18.85.x.x address. The msh0 gives

1. when connected to an AP
   • 169.254.x.x
2. when connected to a school server
   • 172.x.x.x(the current school server in the lab)
   • 10.x.x.x
   • 192.168.x.x
3. when connected in local link
   • 169.254.x.x

DNS check

The most direct way to check internet connectivity is by checking the resolv.conf file. It shows if the XO is registered to a DNS server. It can be viewed with

cat /etc/resolv.conf

• If it is empty there is generally no connection to the internet(technically, no connection to the DNS server)
• If it includes a nameserver with 169.254.x.x address there is internet connectivity through an MPP. The address is in fact the IP of the XO which acts as an MPP
• This is useful to determine on which MPP the XO is connected to, when there are multiple MPPs
• The is a rare possibility resulting from a Network Manager failure, of an XO to have access to the internet, but the resolv.conf to be blank. In that case the XO will not be able to resolve hostnames. This possibility can be examined with

ping www.mit.edu   # No replies
ping 18.7.22.83    # Normal replies  

The general rule of thumb regarding the resolv.conf file in the lab XOs is

• empty: local-link
• 169.254.x.x: MPP
• 172.18.x.x: Schoolserver
• 18.85.x.x: Media lab AP

Telepathy services

The Presence Service acquires information on other XOs in the network, and provides the capability to view them in the neighborhood view, or share with them an activity. This is achieved through two child services, Salut and Gabble.

• Salut runs when the XO is connected to a mesh. It uses the avahi _presence._tcp service.