Re: [Dorset] Bizarre networking problem

[Simon P Smith]

On 20/01/14 20:24, Peter Washington wrote:

On 20/01/14 12:56, Graeme Gemmill wrote:

At least, I think it's bizarre.

Can someone suggest other tests to identify and resolve the problem?
TIA



Graeme,  just a slight aside from me on the powerline devices.

I use these to connect several devices to home networks but recently they
near drove me mad with similar networking oddities that you seem to be
experiencing.   Changes to the noise levels on the building wiring can
really mess up something that may have been previously working.

I have a recent problem where the network between my office (outbuilding)
and house (where ADSL terminates) only works if I have two of these devices
operating.  Previously I also had media player and camera plugged in 
elsewhere.
If I plug in another one locally it seems to desensitize the local ones 
to the remote
device (previously this worked).  I even bought more devices to test as 
recent storms

seem to have knocked out my surge protectors.

Just a though but these devices sometimes stop working in odd ways.

Cheers

Si



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Re: [Dorset] Bizarre networking problem

[Ralph Corderoy]

Hi Graeme,

 Wireless router is connected to:
  PLA 1 (powerline adaptor HP500), which connects to
  PLA2 (powerline adaptor HP500) and
  PLA3 (powerline adaptor HP200), which are geographically 
 separated.
  PLA2 connects to
  Netgear hub which connects to
  DTa
  DTb.
  PLA3 connects to
  Laptop.

I read that as

1 fail:  laptop -- pla3 -- pla2 -- netgear -- (dta, dtb)

 When I connect Laptop by cable directly to wireless router, it sees
 and connects to the required shares.

2 ok:laptop -- router -- pla2 -- netgear -- (dta, dtb)

 When I move the Laptop to connect by cable to the Netgear hub, it sees
 and connects to the required shares.

3 ok:laptop -- netgear -- (dta, dtb)

 In this [1] configuration, Laptop CANNOT ping DTa or DTb, let alone
 connect to the required shares.

Pinging by IP address, not by name?  What's the ARP cache show before,
i.e. when you haven't tried for a while, and after.  See arp(8).

 The inference is that  the PLA1 - PLA3 leg is somehow selectively 
 blocking access to the other leg of the LAN.

It seems from the above diagrams that more than one pla# breaks it.  I
know nothing about these things.  Perhaps the ARP broadcast is only
making it across one of them?

 However..  When DTa, DTb and Laptop all ran Mandriva 2011, there was
 no such problem.

Seasoned admins know to be skeptical of a Nothing answer to What's
changed?  :-)

 Installed Wireshark but can't use it - video problem

tcpdump(8) can still be helpful, e.g. you can watch for ARP packets with
it;  `sudo tcpdump arp'.

Cheers, Ralph.

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