Google Treasure Hunt: Network Question

Network Problem

Network Problem

The network question was by far the easiest one in GTH 2008 contest.

Sample question:

Below is a diagram of a computer network. The nodes are hosts on the network, and the lines between them are links. A packet is sent out from host N with a destination of 201.107.56.70. Which nodes does the packet pass through on its way to the destination? (include start and final node in your answer)

After that, Google presented a list of nodes with their IP addresses, 3 different static routes and a default gateway. This is the entry for host N:

N 97.134.15.173 88.42.227.237 => 53.138.73.76 201.107.56.70 => 179.138.156.133 68.190.198.0/24 => 248.194.205.8 246.10.120.232

Pretty easy:

  1. A packet going to 201.107.56.70 arrives at node N
  2. Does it match 88.42.227.237 destination host? No… next try
  3. Does it match 201.107.56.70 destination host? Yes!
  4. The packet is forwarded to the host having 179.138.156.133 IP address (which is host B):
B 179.138.156.133 31.114.20.211 => 248.194.205.8 53.138.73.76 => 97.134.15.173 248.194.205.0/24 => 67.244.46.98 53.138.73.76

And so forth…

<bonus>

How would route table at host B look like?

devel@stewie:~$ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
31.114.20.211   248.194.205.8   255.255.255.255 U     0      0        0 eth0
53.138.73.76    97.134.15.173   255.255.255.255 U     0      0        0 eth0
248.194.205.0   67.244.46.98    255.255.255.0   U     0      0        0 eth0
0.0.0.0         53.138.73.76    0.0.0.0         UG    100    0        0 eth0

</bonus>