computer to "smart device" - subnet question
Jim Cornette
fc-cornette at insight.rr.com
Sun May 29 14:17:19 UTC 2005
Lai Zit Seng wrote:
> On Sat, 28 May 2005, Jim Cornette wrote:
>
>> Setting the netmask for the computer to 255.255.0.0 allows
>> communication between a computer with addresses in the 192.168.127.x
>> and with devices in the 192.168.2xx.x range. The problem I am
>> experiencing is intermittent dropout of "smart devices" that also have
>> settings for masking and are set to 192.168.127.xx with a mask of
>> 255.255.255.0. The computer ethernet address is set to 192.168.217.14.
>
>
> If the netmask is wrong on those smart devices, they will need to route
> through their default gateway to return traffic to you.
>
> That said, I've seen (and it is possible for these smart devices you're
> referring to) to cache the IP/ARP mapping seen from the first packets
> that your computer sends to the smart devices. That would explain why
> this appears to work. But ARP cache entries will expire. When they are
> gone, the smart devices will try to send the packet according to normal
> IP routing rules: i.e. if not in the same subnet, must route through
> default gateway. If you do not have a default gateway for them, the
> packet is lost.
This seems to describe the problem encountered. I believe a default
gateway is specified, but there is no gateway available with these smart
devices.
>
>> Anyway, could the intermittent dropout with communication be caused by
>> the masking on the smart device not ranging with the IP of the
>> computer or would the broader setting for the computer be enough to
>> not cause a loss of connectivity.
>
>
> You should really try to get the netmask set correctly. You cannot
> depend on a "netmask trick" done on just one end to make it work
> reliably for both ends of a communication.
I'll see what setting the smart device masking to the wider setting to
see if the dropouts cease.
Thanks for the answer and Scott for his answer as well.
Jim
>
> Regards,
>
> .lzs
> --
> http://zitseng.com/
>
--
Some Windows were made to be broken.
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