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I can successfully ping, say, google.com via cmd using:

ping {IP ADDRESS} -T -L 1000

But if I use a packet size greater than "1001" I get a request timed out error. I know that the max amount of bytes I can send out is 65500.

Why is this?

P.S. My Internet is fine and I can access all websites through browsers.

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  • On windows the format for ping is ip address after the options. So you should be using ping -t -l 1000 <ipaddress>
    – DavidPostill ♦
    Commented Jul 2, 2015 at 22:57
  • ping -t -l 9999 www.google.com works here (Windows 7). Perhaps you can give an example that fails?
    – DavidPostill ♦
    Commented Jul 2, 2015 at 22:58

2 Answers 2

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As grawity said in the comments when your packet is larger than the MTU size fragmentation will occur. Because ICMP packets contain very short messages, there is no legitimate reason for ICMP packets to be fragmented. If an ICMP packet is so large that it must be fragmented, something is amiss. For this reason some network administrators will block any ICMP packet that has the More Fragments flag set or that has an offset value indicated in the offset field.

Source

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This looks like an MTU problem. If any router along your path to the destination does not support Jumbo Frames, then your ability to send much more than 1k (total frame size 1500) will stop at exactly that point, and you will end up with dropped frames beyond that hop. Even Jumbo Frames are limited to 9000 bytes, so if you want to send 65500 byte frames, then every router along that path will need to enable Super Jumbo Frames. The referenced Wikipedia article should clarify this issue.

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    Jumbo Frames aren't very important here, as IP already supports fragmentation; a 2000-byte ICMP message over 1500 byte MTU would just be sent as two IP packets.
    – grawity_u1686
    Commented Jul 2, 2015 at 22:49

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