Ping - ICMP packet size?

[K.Vijayaragavan.]

Hi,

I have HPUX 11.00 and i need a calrification on ICMP pcketsize of the ping command.

Man page of "ping" command shows that the maximum size of ICMP echo request packet i can use along with ping command is 4095 bytes.

But when i tried with more than that(4095>packetsize<65000)it still works(pings).

"ping a.b.c.d 65000" works.
But i could not put more than 65000.

why it is allowing upto 65000 when the maximum is defined as 4095 as per the man page of ping?

K.Vijay

[Steven Sim Kok Leong]

Hi,

I don't have a HP-UX system to test right now. Do you have ethereal or tcpdump installed either on the HP-UX? You can verify the size from ethereal or tcpdump. nettl is a bit hard to use. If you are versed with nettl, you can use it to check the size.

Hope this helps. Regards.

Steven Sim Kok Leong

[Johan Gjestvang]

Hi,

Yes you are right. On 11.0 and 11.11 ping work fine with packet-size greater than 4095 even the man-page say 4095 is the max. In 10.20 however, the limite is true.
But even 10.20 can receive and reply to icmp packets greater than 4095 bytes and
pc's have for long time being
able to send icmp requestes
greater than 4095. I has't found any documentation why it is like this. We may consider it as a progress ?

Br,
Johan

[Ron Kinner]

As for the limit of 65000 look up "ping of death" on the internet.

http://www.insecure.org/sploits/ping-o-death.html

is one site but your corporate firewall may block it as a hacker site.


Essentially receiving a ping of more than 65536 bytes will upset most PCs.

Back in the good old days everyone's operating system would refuse to generate a ping any bigger. However, along came Windows 95 and, yes, you guessed it, Microsoft didn't worry about the limit, so instant ping of death generator.

Ron