Trivial question - ping to www.cisco.com

[thisisshanky]

Dont know if Cisco's network doesnt like odd bytes on the ping packets. I am trying to ping http://www.cisco.com with different sizes of data. Every time the bytes size is ODD (like 1001, 1003, 1005 etc) the ping fails. Even byte sizes gives me a success. To be specific the lower limit on the ODD byte size is 17 bytes. Any ODD number of bytes above 17 (say 19, 21 ) seems to fail.

I have used two different laptops, two different internet connections to test this and it behaves the same. Command used is,

ping -l <bytes> http://www.cisco.com from a command line.

Also the max even byte size you can set is 1464 bytes. (leaving remaining bytes for frame headers and stuff)

I havent seen this problem with any other websites ( a few that I tried include http://www.yahoo.com, http://www.google.com etc)

Weird, but interesting...

[milan.kulik]

Hi,

couldn't that be something like this:

http://www.cisco.com/en/US/products/hw/switches/ps607/products_field_notice09186a0080094bf1.shtml

Regards,

Milan

[Kevin Dorrell]

That figures. Below 18 bytes, the frame is being padded to 64-bytes - an even number, keeping the CRC on an even boundary. That really does suggest the problem is at the level of Ethernet. And given that it works on other sites, the problem must be in http://www.cisco.com.

Nice one!

Kevin Dorrell

Luxembourg

[thisisshanky]

Nice finding! Milan..

Looks like Cisco will have to go back and patch their NIC drivers (if they are intel).

[t-gestiona]

I think they (Cisco) are blocking ICMP traffic in order to avoid any sort of attack