clueless: ICMP is a security risk.
cluefull: ICMP is a mandatory compoment of the
TCP/IP (that is the protocol stack of the Internet). It is required for TCP to work correctly.
It is required for UDP to work correctly. It required for a couple of other
famous transport layer protocols to work correctly. see here
clueless: You can't use the first and last subnets.
cluefull: You can use each and every subnet.
You can also make subnets of different sizes. You can make supernets out of a bunch
of classfull networks. It's called CIDR. It's been around for 10 year. Where have
you been? More here and here
clueless: Classless routing is a security risk.
cluefull: Bullshit. Classless routing is mandatory part of the internet routing architecture as of Sep 1993. See here
clueless: You need all 8 wires to run a full-duplex 100BASE-TX connection
cluefull: Bzzeet. Wrong answer. You need the same 4 wires as with half duplex - pins 1,2,3,6 on the RJ-45 connector. more here
clueless: To connect two Ethernet 100BASE-TX cards or two hubs or two switches, or a hub to a switch to one another you need to make a rolled cable. That is on one end pins from left to right, on the other pins from right to left.
cluefull: No. A rolled cable will never work. First of all your cards or hubs or switches may support "Auto MDI-X", so a straight cable may work right away. If they don't you have to make a crossed cable. That is on one end
[
wor,
or,
wgr,
bl,
wbl,
gr,
wbr,
br
] and [
wgr,
gr,
wor,
bl,
wbl,
or,
wbr,
br
] on the other. More here