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Home > Archive > CCNA > March 2004 > another tough one..
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another tough one..
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| worrywarm 2004-03-22, 6:20 pm |
| Two Cisco 7204 are connected by a long-distance Ethernet circuit over a layer-2 fiber platform. Small pings across the link have close to 100% success rate. Large pings have a 30% failure rate. What are the likely causes of the problem.
I don't have a clue..
anyone knows? Thanks a lot. | |
| Yankee 2004-03-22, 7:46 pm |
| Is this a book question or real world? If it is a book, I would be looking at buffers.
Yankee | |
| worrywarm 2004-03-22, 9:26 pm |
| this is a question to test the real world hand on experience (not from a book). It requires you give the possible guess and the way to troubleshoot it and prove your idea.
any more suggestions?
thank you. | |
| Yankee 2004-03-23, 8:39 pm |
| I am hard pressed to give you a real world answer if someone has not messed with default buffers and that would be obvious in the config.
Yankee | |
| worrywarm 2004-03-23, 11:52 pm |
| PING - Dropped packets
Detect them by noting when the sequence numbers skip, and the missing number does not appear again later. This is probably caused by a router queueing packets for a relatively slow link, and the queue simply grew too large. Early TCP implementations dropped packets at a truly alarming rate, but things have gotten better. Even so, there are common situations, typically involving crowded wide-area networks, in which even modern TCP implementations can't operate steady-state without dropping packets. There's no reason to pull your out hair over this, since TCP will retransmit missing data, but this won't make your network run faster. Also, if you have fast links that aren't showing much congestion, the cause of trouble may be elsewhere - link-level failures are the next most common cause of packet loss.
It seems the most likely cause is buffer, but what I'm confused about is small ping would send out 5 ICMP msgs, and large ping would send out 5 ICMP msgs by default too (although you can change it), why it will make a differece on packet loss???
weird question. | |
| Yankee 2004-03-24, 5:38 am |
| there are different buffers for different size packets, so that is why I guessed buffers. Generally speaking it is a bad idea to mess with buffer settings because you are most likely dealing with a symptom and not the cause of a problem. You are much better off to fix the cause than fight a symptom.
Yankee |
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