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packet loss problem

Dear sir,

we are facing a very weird problem ,

we have a link at 15mb , router a , router b router c ,

ping from router a to router b no packet loss - ping from router b to router c no packet loss , ping from router a to router c we are seeing up to 6% packet loss.
we are using the vyatta router on location a and b , on location c cisco switch

1 Solution
Do you see a loss when you ping from router c to router a?
all packet loss occurs with ICMP packets only???? or you have an applicaiton failing? You might look to your encapulation setup, and MTU sizes. I'm not familure with vyatta equipment, but i'm sure that where your problem is. what is the topology? send a little mspaint example with link speeds, encapulation(s), and if its across a WAN or not.

Is the link between A and B, the same speed as the link between B and C?
Could be a bottleneck.
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nad_xtAuthor Commented:
the link speed between a and b is 50MB wan pipe , we are using maximum 25mb from this pipe , and no packet loss at all from ato b , from b to c the pipe is 100mb there is a cble between cisco switch and dlink 3526 layer 2 switch , ason port no error at all .

As sullivan stated, check the MTUs to be sure it is not a fragementation issue, but also check to see that all the interfaces are negotiating at the correct speed/duplex.  A lot of times on ciscos you will see a duplex mismatch between what is set on the router and what an autonegotiating switch will try set its connecting port to.  
You may be able to get into the console of the cisco switch and turn on debugging  to see if you get any errors like this.  However typcially if you are connected to the device via console cable using hyperterminal or similar program the device will display all errors on the screen. So you should just be able to connect and wait a while to see if an error pops up on the screen.
nad_xtAuthor Commented:
dear sir thanks for your notes and help, i will try the several tests
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nad_xtAuthor Commented:
dear sir,

regarding the packet loss i did notice on the switch port the folowing
   RX Frames                                  TX Frames
                ----------                                 ----------
CRC Error       32495                Excessive Deferral    0        
Undersize       0                    CRC Error             0        
Oversize        0                    Late Collision        0        
Fragment        41                   Excessive Collision   0        
Jabber          21                   Single Collision      0        
Drop Pkts       0                    Collision             0  

is the fragment and jabber cause this type of packet loss, and what could be causing

thanks again in advance
I personally doubt that MTU would be an issue, unless you are ping'ing with a large pay load.  The default payload size from any device/OS is smaller than the minimum MTU required by IP.

Are you having a problem other than the dropped packets?  Are you constantly ping'ing the device?  Is there always a packet loss?  Or does the packet loss only happen specific times of the day?

I am also confused on what the link speeds are.  Originally you stated that a to b was 15 Mbps, then you stated it was 50 Mbps with 100 between b and c.  So  could you clear this up, I am assuming you have something like:

   LAN#1 <-- 100 Mbps > RouterA <---  ? Mbps ---> RouterB <--- 100 Mbps ---> RouterC <--- 100 Mbps ---> LAN#2

What is the speed of "?"?

Which switch port did you notice the CRC checks?  You may want to clear the counters on that port and monitor for awhile.
And where do the cisco and dlink switches fit into all of this (where are they deployed, and to what are they connected)?

>CRC Error       32495                
CRC errors are indicators of physical issues like bad wiring. Suggest replacing the cable between this device and the switch.
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