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Re: question about network connections

On Sat, 26 Oct 2019 11:57:19 +0100
mick crane <mick.crane@gmail.com> wrote:

> hello,
> what tests can I do to find out what is happening with internet 
> connection ?
> I have pfsense as router connecting to ISP's broadband box.
> I think pfsense does that DHCP but also I might have names to
> ipadresses in host files but just for local network addresses.
> I have debian apache on local network offering a page with links like
> my bookmarks
> Problem is there is one site that sometimes it loads sometimes it
> times out.

That has something of the sound of DNS, though bear in mind that some
sites do drop out/get busy for a few seconds. I've known Firefox to
tell me that it can't find Google, and an immediate retry works.

> I connect from windows-> apache web page of links-> internet site.
> I've run wireshark in the past but have no idea what to make of the 
> results.
> What can I run and where to see where is not working ? If is me or
> them.

Start with DNS. What DNS does the workstation use? Try something
different. If it's using your router or ISP, try OpenDNS or something
else outside the ISP's network.

Also try traceroute to the offending site at various times to see if
you get a consistent time or whether there is a blockage somewhere.

As you say, Wireshark can be difficult, though it has very powerful
filtering once you know what you're looking for. Again look for TCP/53
outgoing and replies.

A simpler alternative for some jobs can be the firewall. I'm still on
iptables, and if I'm having trouble with a particular type of packet,
I'll make (or more likely, reenable) a couple of logging rules to give
me at least a basic understanding of what is going in and out.


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