Re: ping subnet

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On Tue, 9 Aug 2005 19:58:57 -0400, "David H. Lipman"
<DLipman~nospam~@Verizon.Net> wrote:

>I'm not sure the IP stack can handle it and are you really sure you want to put that much
>traffic on the LAN ?

The IP stack can definitely handle this. As written the script
Charles put together would only ping each address twice. A scope of
254 addresses doubled would be 508, doubled again for the replies,
would be 1,016 packets over more than 10 seconds. Each packet ICMP
packet would likely take up a 64 byte ethernet frame, so this would
likely take 6,502 bytes of IP over eithernet traffic per second.
Considering that a 100Mb connection can do 12,500,000 bytes per
second, we're probably covered.

Now, we're the majority of the traffic on a LAN will come from is from
the ARP broadcasts. The total amount of bytes will depend on how many
nodes are on the network (assuming a switched network... does anyone
use hubs anymore?). Each ping will cause an ARP to be sent except for
know MAC addresses.

ARP traffic will typically hit every node on the VLAN/collision
domain. If an ARP reply is not received by the time the 2nd Ping
packet is ready to be sent then another ARP request is sent via
broadcast.

So the worst case is that two ARP requests are sent out for each IP
and there is one successful ping packet sent and a reply received.
That would be about 43,300 frames per second ((254^2 * 2 + half of the
ping packets), which to make the math simple would take about 1/3 of a
percent of the possible bandwidth.

Here's a batch routine I put together for getting MAC addresses
quickly, and I watched a Sniffer while testing this.

http://groups.google.com/group/microsoft.public.win2000.cmdprompt.admin/msg/dfc3acf5a689b214?hl=en&;

Thanks,
Clay Calvert
CCalvert@xxxxxxxxxxx
Replace "W" with "L"
.

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