[gentoo-user] Re: Curious ping problem with no FW

[Harry Putnam <reader@newsguy.com>]

Mick <michaelkintzios@gmail.com> writes:

> On Monday 14 July 2008, Harry Putnam wrote:
>> I've had a problem with being able to ping out to the internet from my
>> gentoo box, while at the same time I'm able to ping outbound from
>> several windows boxes on same home lan.
>>
>> I don't run a firewall at all from linux but do have a Netgear
>> switch/router/Firewall upstream between me and the internet cable
>> modem.
> [snip..]
>
>> My router/fw can be set to deny specific machines outbound traffic but
>> that is not done in this case.  So the solution must reside somewhere
>> in my gentoo install.
>
> It may be worth checking your router's firewall rules once more.  Is the 
> gentoo box connected to the router in the same fashion as the MSWindows 
> boxen, or is it in some funny DMZ set up?

The section involving blocking has nothing whatever set.

> What do the firewall logs show?

Since there is nothing outgoing set to log, it says nothing.

>> What things should I be checking.
>
> If as you say you have no firewall on the Gentoo box then you ought to have a 
> quick look at your kernel.  Use sysclt:
>
> /sbin/sysctl -a

Here I see:
  sysctl -a|grep 'net.*icmp'

  net.ipv4.icmp_echo_ignore_all = 0
  net.ipv4.icmp_echo_ignore_broadcasts = 1
  net.ipv4.icmp_ignore_bogus_error_responses = 1
  net.ipv4.icmp_errors_use_inbound_ifaddr = 0
  net.ipv4.icmp_ratelimit = 250
  net.ipv4.icmp_ratemask = 6168

But not sure what any of it means.  The first line looks kind of
ominous though.

>> A ping attempt like this:
>>
>>   ping ftp.ucsb.edu
>>   PING ftp.ucsb.edu (128.111.24.43) 56(84) bytes of data.
>>
>> Just never moves any further, but you can see it has resolved the
>> alpha address to numeric forum so must have contacted and received
>> info from the nameserver.
>
> Or from your router if it acts as a caching DNS resolver?

I don't think so, at least there is no mention in the documentation of
such a feature.