Esoteric question

[Gregory Sloop]

So, the provider came in and replaced the cable-modem and that made the problem vanish.
I'm going to see if I can get ahold of the problem modem, and *if* I get some time, I'll see if I can tease out what might have been the root cause.

I wouldn't be holding my breath waiting for it, but we'll see.
It certainly was a *very* odd situation - and I'd love to know the cause.

-Greg


Not to "diss" any of the prior suggestions - but THIS, well this is something I can get behind!

It *might* not be correct, and it's a bust of an idea - but it, IMNSHO, ties all the pieces together in a really elegant way.
It's just a concept that makes so much sense and makes all the weird symptoms all seem so much more plausible.

Wow. Really, massive thanks Simon.

I'll try to update the list when/if I figure out what's wrong. [Unless I've done something so incredibly stupid I'm too embarrassed to post about it... :( ]

The modem did get replaced today, so it's possible the symptoms simply vanish because of some change in the modem config, etc. But we'll see.

Thanks so much all!

-Greg

SH> Gregory Sloop <gregs at sloop.net> wrote:

>>Packet caps from the new router show that the router/DHCP server IS
>>seeing all the DHCP protocol handshake. [When it's having the
>>"problem."]
>>The client does a DISCOVER
>>Server responds with OFFER
>>The client responds with REQUEST
>>Then there's a LONG pause. [like 90s+ worth.]
>>The Server responds with ACK. [It actually appears to send several
>>ACKS.

SH> Ah, about 90s you say ?
SH> Have a look on the external interface and/or in the logs and see
SH> if it's trying to do any DNS lookups or updates. Over the years
SH> I've seen lots of threads related to 90s delays - a common one
SH> being SSH logins - which have come down to the device attempting a
SH> DNS lookup and waiting for it to time out.

SH> Anyway, what I theorise could be happening is :
SH> With WAN connected, "something" (dhcpd) is trying to do
SH> "something" with an outside service and timing out.
SH> When the WAN is link-up but not connected to the modem, such
SH> attempts fail very quickly as the device has no ARP entry for it's
SH> default route and so the network stack quickly reports "no route to host".

SH> BTW, when I first read your post I was thinking WTF ! It was only
SH> after reading the other replies that this idea came to mind.

SH> Simon
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