nanog mailing list archives

Re: job screening question


From: Owen DeLong <owen () delong com>
Date: Sat, 7 Jul 2012 19:32:25 -0700


On Jul 7, 2012, at 5:44 PM, Keith Medcalf wrote:

"What's the problem with using 255.255.255.247 as a subnet mask if you
want to make a LAN subnet with 12 hosts?"
(5 word answer)

Unemployment Office Is That Way ->

Is the only 5 word answer I could come up with.  The correct answer "invalid netmask", is only two words.


LoL...

Even if you allowed for discontiguous subnet masks, you'd need to use 255.255.255.243 and not
255.255.255.247 to achieve 12 hosts.

Not sure what 5 word answer you're looking for, but Keith's answer and mine are the two most obvious
issues I can think of.


"What TCP destination port numbers should be allowed through the
perimeter stateful firewall device to and from a mail server whose
only purpose is to proxy SMTP mail from internal sources?"
(one number answer)

Short Answer:  There is no answer to the question that can be expressed in one number.

Sure there is, if you count "none" as a number.

Outbound connections to TCP destination port 25 only.  Returning traffic (including associated ICMP) should be 
automatically handled by your stateful inspection firewall.  If not, you need to buy a better firewall.

I'd allow 25 and 465 outbound, myself. No reason to block SSL if the remote side offers the capability.

ICMP wouldn't be a TCP destination port number anyway.

Any applicant who provides any answer should the rejected out of hand as (a) being unable to read (b) being a threat 
to security.

LoL... Some truth to that.

Owen



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