Problem with 3750

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Jul 8th, 2010
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I have a simple question that I can't answer.

I have a Cisco 3750 that whenever I pefrom the command "Show interface vlan2222 | i rate " I get the following output:

Cisco3750#show  interfaces Vl2222 | i rate

  Queueing strategy:  fifo

  30 second input rate 0 bits/sec, 0  packets/sec

  30  second output rate 0 bits/sec, 0 packets/sec

There is definitely traffic passing on this L3 Swtich and I don't understand why it's not providing me with the weight of the VLAN.

Why is the input / output rate at 0? with 0 packets..??


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djh278778 Thu, 07/08/2010 - 09:22
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You will not see counters on this interface unless traffic is sent TO the IP address of interface vlan 2222 or if traffic is sent FROM  the IP address of interface vlan 2222. Traffic that passes through vlan 2222 without hitting the layer 3 address should not generate counters. Try a test, ping the ip of that interface and then check it.

Mavrick25 Tue, 07/20/2010 - 04:57
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I tired perfroming the ping test are you absolutley right.

I began to see the counters..

The problem is that I don't see my traffic...

I checked and the VLAN's ip address configured on the switch is the default gatway for the device passing me traffic.. I don't understand why it's not counting it..

djh278778 Tue, 07/20/2010 - 09:01
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I am not sure because I am unaware of your topology and configs, but it could be that the destination host MAC address is already known by the source host thereby not needing to forward traffic to the default gateway.   Just a thought, hope it helps.

Nagaraja Thanthry Tue, 07/20/2010 - 09:19
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If the switch has already build CEF table and switching the data in hardware, then you may not see any increase in the interface counters as all the packets are handled in hardware. You could use the command "show interface stats" to see the traffic through the specific interface. You can also use "show interface accounting" to see type of packets that are punted to the CPU.

Hope this helps.



Nagaraja Thanthry Tue, 07/20/2010 - 09:23
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To add to my earlier post, there is a software defect filed in this regard and the conclusion is that it is the hardware limitaion on the lower end platforms.

Here is the bug ID: CSCsi44166

Hope this helps.



Mavrick25 Wed, 07/21/2010 - 00:42
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Thanks again for all your help, it's only fair I shed some more light on what is going on.

The topology?

Cisco 3750 -------------> DSLAM

config of 3750 on interface

interface Vlan2222
description link to DSLAM in question
ip address 10.x.x.115
ip access-group 5555 in
no ip redirects
no ip proxy-arp

Where the DSLAM's ip address is part of the /29 network, the DSLAM is configured with 10.x.x.115 as the default route.

If I purform the following commands that were suggested this is the output:

show interfaces vlan 2222 stats
          Switching path    Pkts In   Chars In   Pkts Out  Chars Out
               Processor    1396895  165390042      54579   32861660
             Route cache      10202     843179         84       9410
                   Total    1407097  166233221      54663   32871070

show interfaces vlan 2222 accounting
Vlan2222 link to
                Protocol    Pkts In   Chars In   Pkts Out  Chars Out
                      IP    1391534  165082859      49152   32322094
                     ARP       5505     330300       5512     330720

I think this is a hardware bug..

Let me know what you guys think..

Thanks again for all you help..



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