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Contributor II
Posts: 70
Registered: ‎05-01-2015

How to capture 802.1q packet in the trunk ports?

Hi guys,

 

I was trying to capture a 802.1q packet from a trunk port,but it wasn't successed.

 

My topology is PC---SW(aruba 1500)--controller(3600).

From PC to SW is access port which belongs to VLAN 10; from SW to controller is trunk port which allows all the vlans.

Also I set 2 SVIs in the SW,interface vlan 10 = 192.168.10.1/24, interface vlan 20 = 192.168.20.1/24.

The PC's IP address is 192.168.10.2/24,its gateway is 192.168.10.1.

In the controller,I set a SVI which is interface vlan 20,IP address is 192.168.20.2/24,

 

For now, I can easily ping 192.168.20.2(the IP address of controller) from PC side, but when I captured the ICMP packets from the trunk port, it only showed ethernet II protocol and IP protocol, and nothing between them.

 

The three ways I used to capture the packet:

1,Mirroring the trunk interface in controller.

2,Mirroring the trunk interface in SW.

3,Add a hub between the SW and controller.

 

Also I tried to change the setting of my NIC card,enable vlan tagging or disable it.

 

Please someone tell me, where am I wrong?

 

PS:I can capture the 802.1q packet from the GNS3 with the CIsco IOS.

 

Guru Elite
Posts: 8,637
Registered: ‎09-08-2010

Re: How to capture 802.1q packet in the trunk ports?

Most laptops cannot see 802.1q headers. Best bet is to use the packet-capture command in the controller because it will encapsulate into GRE and preserve the headers.


Thanks,
Tim

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How to capture 802.1q packet in the trunk ports?

I can see the 802.1q header for GNS3,same laptop.

And I didn't use wireless,this is all wired.

Guru Elite
Posts: 8,637
Registered: ‎09-08-2010

Re: How to capture 802.1q packet in the trunk ports?

For GNS3, are you capturing your physical NIC or a virtual interface?


Thanks,
Tim

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How to capture 802.1q packet in the trunk ports?

[ Edited ]

Yes,from the real NIC card,I can see the 802.1q tag.

 

You can see the ICMP traffic from 192.168.10.2 to 192.168.20.2.

Guru Elite
Posts: 8,637
Registered: ‎09-08-2010

Re: How to capture 802.1q packet in the trunk ports?

I would still just use the packet-capture command.


Thanks,
Tim

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How to capture 802.1q packet in the trunk ports?

Could you please tell me more about this command?

 Then I can try it tomorrow,thanks.

Guru Elite
Posts: 8,637
Registered: ‎09-08-2010

Re: How to capture 802.1q packet in the trunk ports?

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: How to capture 802.1q packet in the trunk ports?

[ Edited ]

Is that port mirririong ?

If so, I have already tried.Both controller side and SW side.

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