Wednesday, April 28, 2010

traceroute scanning

something that's lots of fun to do is to scan a network with a traceroute command. what you get back is a (relatively) complete picture of the network connecting all the hosts with the specified prefix. depending on where you point it, it can be very, very big.

like i mentioned earlier, i know which node it is that stands between me and several routers that connect to different parts of the Boston internet. one of those routers goes to NOX, and another one to other residential (i think) comcast accounts. if i point the traceroute scan at a comcast node that's relatively nearby, and that contains the same IP prefix as mine (20 bits is reasonable and doesn't give back 65 thousand possible hosts), i get back a nice, complex picture of a network extending from here and across Boston, and across MA to CT, VT, and the MA-NY border.

i tried the same thing on the private 192.168 network at the institute, and got back something similar, and actually much denser (which makes sense, all hosts within the network have the same prefix, so i could get them all in one big shot, but the comcast network was relatively sparser, and seemed to have same-prefix hosts separated by nodes with different prefixes, which i don't understand...). since it's a single institution, it's organized differently - there are nodes for different users, but mainly the network divisions are more functional, with databases in one place, outgoing servers in another, administrative here, labs there. the comcast network looked much more regional, with a Hartford node, others (i get all these new englandy names confused, they all sound like Westly or Chestford or something like that).

ok, need to step back now and get more acquainted with the specifics rather than just playing with these toys...

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