Networking problem

JD jd1008 at gmail.com
Sun May 15 04:40:50 UTC 2011


On Sat, May 14, 2011 at 9:09 PM, Shane Dawalt <sdawalt at donet.com> wrote:

> On 05/14/2011 10:59 PM, James McKenzie wrote:
> > On 5/14/11 7:41 PM, Kevin J. Cummings wrote:
> >> On 05/14/2011 10:09 PM, JD wrote:
> >>> On 05/14/11 18:45, James McKenzie wrote:
> >>>> On 5/14/11 6:40 PM, JD wrote:
> >>>>> On 05/14/11 18:24, Joe Zeff wrote:
> >>>>>> On 05/14/2011 01:27 PM, JD wrote:
> >>>>>>> I also brought the fedora firewall down, and retried to ping Fedora
> >>>>>>> from Powerbook. No go!!
> >>>>>> That means that it's not a firewall issue.  Check your router config
> to
> >>>>>> see if it's set to allow pings inside the LAN.
> >>>>> Thanx!
> >>>>> I checked. The gateway has a built-in feature (program)
> >>>>> to let you ping any client on the lan (or any ip on the public net).
> >>>>> The gateway can ping both the powerbook and the fedora pc.
> >>>>> no problems there.
> >>>>> The fedora pc and the powerbook can ping the gw, and a third machine
> >>>>> connected to the GW by ethernet, and can of course ping addresses
> >>>>> on the public net.
> >>>>> They (fedora pc and powerbook) cannot ping each other!
> >>>>> Powerbook firewall is set to promiscuous mode.
> >>>>> And as I had stated earlier, I even stopped iptables on the
> >>>>> fedora pc, which puts it also in promiscuous mode (I assume).
> >>>>> Still these two machines refuse to talk.
> >>>>>
> >>>> Can you use traceroute to communicate between the two of them?
> >>>>
> >>>> James McKenzie
> >>>>
> >>> Tried it.
> >>> Tracerout is unable to get to target after 30 tries.
> >>> All it shows is asterisks.
> >> Sounds to me like traceroute is trying to go "direct" between
> machines....
> >>
> > That it is if the two devices exist on the same subnet, which is a bad
> > thing for wireless.  Your suggestion on how to solve this is 'spot on'.
> > Unless traffic is local, it should go to the gateway on wireless.  Wired
> > is much different.
>
>    Wired and wireless are essentially the same.  They all adhere to the
> IEEE 802.3 spec and the 802.1 bridging paradigms.  Copper, light, air
> ... it's all in the physical layer as stipulated in IEEE 802.3.  Once
> the electrical signals are delivered, then it becomes IEEE 802.1 for
> bridging and all the RFCs for IP and ICMP, TCP and UDP and etc.  You can
> build a network with 254 hosts (192.168.1.1 - 192.168.1.254) using both
> wired and wireless and it works quite well.  I've done that in my house
> for the last 10 years.  I work at a place where we have 40 buildings
> with 20 wireless networks that span virtual-LANs across our campus
> connecting to routing interfaces throughout the campus.  But, as one
> poster has already pointed out, there are different modes of the radios
> that can cause problems.
>
>   However, the OP appears to be pinging wired machine (having an en1
> interface) from a wireless machine (having a wlan interface).  If this
> is true then the radio mode shouldn't make any different.
>
>   I'm almost ready to break down asking for ARP information.  But I
> think we have one other test before diving deep into the dungeons.
>
>   One thing confuses me here.   The OP is trying to ping 192.168.1.60.
> Yet, the physical interface of the ifconfig listing for machine at
> 192.168.1.60 shows en1 as having 192.168.1.70.  In fact, there is no
> physical interface on that computer having 192.168.1.60 configured on
> it.  However, there is a route table listing that says to get to
> 192.168.1.60, packets should be routed to localhost (127.0.0.1).  Here's
> an excerpt of what I am describing:
>
> 192.168.1.60       127.0.0.1          UHS         0        0    lo0
>
>
>    So, the next question is; is there something in the host that is
> actually listening for packets destined for 192.168.1.60?  Because at
> this point, it looks like any packets destined for 192.168.1.60 hit
> 127.0.0.1 and then die for the lack of a responder.  The machine won't
> respond, because there is no physical interface having an address that
> matches the destination of the packet.
>
>   My next test would be to try pinging 192.168.1.70 from the
> 192.168.1.108 machine and see what happens.  (Of course, modify the
> iptables of the 192.168.1.108 machine appropriately.)
>
>   Shane
>
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Sorry!
My bad.
Because I am doing my email on the fedora machine,
I can only look at the powerbook machine and do a visual
transcription of the output of the commands. So, my typing
is not so accurate.
I should proof read before sending :)

on the Powerbook, en1 is the wireless interface, and en0 is the wired
interface.
So, both the Fedora PC and the Powerbook are wirelessly associated with the
router.

So, I am pinging 192.168.1.70 from 192.168.1.108 (fedora) and it fails.
Vice versa (on the powerbook - 192.168.70), also fails.

I think this weird problem is most certainly caused by the router.
It has bad firmware!!
This router also has individual firewall for each connected client.
All of them are identical, except for the Fedora machine, for which
a few ports are opened up. That's all.

GW can ping wireless 192.168.1.70 and 192.168.1.108 and wired 192.168.1.1
192.168.1.70 and 192.168.1.108 can ping the whole world except each other.
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