[Gllug] hourly/daily rate for linux systems admins?

[Jason Clifford]

On Tue, 2010-11-23 at 11:33 +0000, Karanbir Singh wrote:
> Eg. One person 
> who came to the interview was unable to confirm how many IP address's a 
> single eth interface can host. While another instantly confirmed : 254. 

Wrong!

An interface can easily support many more addresses than that. If you
want to test this try the following (these are bash but you get the
idea)

for i in `seq 1 254`; do ip addr add 10.1.0.$i/16 broadcast 10.1.255.255
dev eth0; done
for i in `seq 1 254`; do ip addr add 10.1.1.$i/16 broadcast 10.1.255.255
dev eth0; done
for i in `seq 1 254`; do ip addr add 10.1.2.$i/16 broadcast 10.1.255.255
dev eth0; done

Then run 

ip addr show

You will see eth0 has at least 762 IP addresses assigned. You can carry
on adding more if you like.

I'm fairly sure there used to be an option under /proc/sys/net to set a
maximum (there still is for IPv6) but I cannot find it now. 

In any event any such limit will always have just been a kernel
parameter. 

It may be that the ipconfig command could have a hard limit but that's
not a limit on what an eth interface can host at all.

I'm always rather surprised to see people lending any weight at all to
such vague and meaningless questions in a recruitment process. This kind
of question doesn't really tell you anything except perhaps that the
second candidate was able to bamboozle you with some kind of answer
albeit one that wasn't actually correct for the given question.

Did the first candidate at least answer that he did not know off hand
but could tell you given a minute on a test box or with google?

Jason

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