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MarcoM
Beginner

Mirroring (SPAN) on Switch WS-C3750-24TS

Hi all,

i have a switch WS-C3750-24TS with release 12.2(20)SE3.

I would like to create a span port and to be able to mirror only the vlan interested.

 

I added these two commands to configuration:

 

monitor session 1 source vlan 1 , 200
monitor session 1 destination interface Fa1/0/24

 

but on destination port i receive always traffic untagged.

 

So i read on other forum to enable this command:

 

monitor session 1 destination interface Fa1/0/24 encapsulation replicate

 

but also with this command the result is the same.

Is there a way to get packets tagged on the destination port of span? is a limitation of this switch?

 

Thanks in advance.

 

 

8 REPLIES 8
Meheretab Mengistu
Rising star

Hi Marco,

I saw that you have tried "monitor session 1 destination interface Fa1/0/24 encapsulation replicate". Have you tried while configuring the destination port (fa1/0/24) as a 'trunk' port?

HTH,
Meheretab
HTH,
Meheretab

Hi Meheretab,

i tried to configure destination port as trunk but no avail:

 

interface FastEthernet1/0/24
 switchport trunk encapsulation dot1q
 switchport mode trunk

 

Any ideas?

Thanks

Marco

Mark Malone
VIP Mentor

is your destination port set as trunk and are you spanning a trunk port as a source too

 

see this too may help  

https://wiki.wireshark.org/CaptureSetup/VLAN

Hi Mark,

i need to span only vlan defined on switch (in this case tag 1 and tag 200), so i defined only trunk destination port no other source port defined as trunk. Makes sense?

 

Thanks,

Marco

Hi
I thought from memory you need to span a physical trunked interface to receive tagged packets , the vlan wont suffice , I think you need to span the trunk itself to see tags

looking at another post there saying same thing there needs to be a source set as trunk , you could easily test it to see , if its only those vlans you can filter on span too

https://supportforums.cisco.com/t5/lan-switching-and-routing/span-traffic-with-vlan-tag/td-p/2128464

Hi Mark,

I have the same problem that the user had.

When configure span on destination port i have only this option:

 

Switch(config)#$sion 1 destination interface Fa1/0/24 encapsulation ?
  replicate  interface replicates source encapsulation

 

the dot1q option is not available. I tried to configure source port with trunk but without results.

I do not understand if the problem is related to the switch model or anything else.

 

Thanks,

Marco

MarcoM
Beginner

Hi all,

so for this switch model you can not have a span port with tagged vlans?

 

Thanks.

sorry slow reply I checked several 37s I have in production none of them seem to have that statement available to configure , if you check the feature navigator it may confirm further

http://cfn.cloudapps.cisco.com/ITDIT/CFN/