[TriLUG] Roadrunner Port Blocking issues / tech support hilarity

[Aaron S. Joyner]

erik at underhanded.org wrote:

>While he can use Instant messaging programs, and do most web browsing
>(along with some https sites I had him check), he can't access certain
>ones that he could before.  Just random outages.  And while talking to
>him, apparently his IP address ends in .255, which doesn't sound kosher
>to me.
>  
>
A lot of ISPs will block source addresses that end in .0 or .255.  This 
is unfortunate, because in larger than /24 subnets (i.e. /23 or 
255.255.254.0 for example) you can certainly have "valid" addresses that 
end with 0 or 255.  To compound the problem, it may not be that the 
destination sites he's trying to access are blocking his traffic, but 
that some host along the way in the middle is.  And of course, due to 
the dynamic nature of routing on the internet, that path may not be the 
same from day to day, so some sites may have intermittent problems.

It's most likely that that address is the core of his problem, and the 
simplest solution (sad but true) is going to be turn off his cable modem 
for X amount of time (probably upwards of 3 to 6 hours), long enough for 
his lease to drop, and then turn it back on.  Best of luck in getting a 
hold of someone with the power to actually drop his lease, not to 
mention fix the root cause of the problem (that being a DHCP server 
which is handing out potentially problematic addresses).

Aaron S. Joyner

PS - Of course another option is to migrate to a better managed 
network.  See http://www.intrex.net/ for one such example.  *grin*