Take the 2-minute tour ×  I do get the following error
message(s) when running apt-get update:  Err
http://nl.archive.ubuntu.com precise-backports/multiverse i386
Packages 503 Service Unavailable  The server is not behing a
proxy, but there is a firewall, I suspect that the firewall is
causing me troubles (transparant proxy?).  What kind of checks
can I perform to be sure it is the firewall and not something
else? Which specific ports should I check in which way to get
conclusive evidence?  share|improve this question add comment  1
Answer  Navigate to your "Software Sources" ( I do not know
which "buntu" you are using). Try a different server either in
your country or in a nearby country. It works for me, when I
occasionally get this problem.  Good Luck   share|improve this
answer add comment  Your Answer