I need to simulate traffic with double tagged vlan on internal LAN. For better describe attaching picture.
I have 2 phones, which make internal call between them. Both are connected to different switches. I need to duplicate traffic between phones, but in addition before duplicating I need to double tag vlan with q-in-q and then send double tagged traffic to server which is monitoring that traffic. I need to simulate this to have same result as customer which don't want provide configurations and we need to fix our product based on that.
Is q-in-q supported on 3560? documentation didn't tell me a much.
Could somebody help me with some sample configuration?
The Catalyst 3560 does indeed support Q-in-Q. Regarding the configuration, ports between the Cat3560 switches will be configured as normal trunks using the switchport mode trunk command. Ports towards "clients" that send tagged frames themselves will be configured using the following commands:
switchport mode dot1q-tunnel
switchport access vlan S-VLAN
where the S-VLAN is the VLAN inside the service provider network used to encapsulate and carry all traffic of this customer.
It is also suggested to use the vlan dot1q tag native global configuration command to prevent Cat3560 from untagging any frames, possibly leading to VLAN leaking that can sometimes occur in Metro Ethernet environments under specific circumstances.
Performing a local SPAN session on trunk ports carrying double-tagged traffic is no different from doing any other SPAN session, however, remember to use the encapsulation replicate command when configuring the SPAN session, i.e.:
monitor session 1 source interface Fa0/23 ! suppose that Fa0/23 is the trunk port
monitor session 1 destination interface Fa0/24 encapsulation replicate ! Fa0/24 is the monitoring port
Also, it has been my observation that Windows have troubles showing any VLAN tags in received frames - this is caused by the NIC drivers. Linux usually has no problems with this.
Each your 3560 has two specific ports: one towards an IP phone, the other towards the 3750 distribution switch. I assume you want to see the voice traffic to be actually double-tagged on trunks between the 3560 and 3750. Am I correct here?
If yes then the port towards an IP phone shall be configured as follows:
switchport mode dot1q-tunnel
switchport voice vlan 7 ! the voice VLAN
switchport access vlan 77 ! the S-VLAN
cdp enable ! we need CDP for the voice VLAN autodiscovery
VLAN 77 here will be the S-VLAN.
Ports between the 3560 and 3750 switches shall be configured simply as:
switchport trunk encapsulation dot1q
switchport mode trunk
Monitoring will be performed using the monitor session commands I have indicated in my previous reply. You can monitor any trunk port, either on the 3560 or on the 3750. In any case, the monitoring PC must be connected to the switch where you perform the monitoring.
I do not understand, though, why do you need to perform the double tagging in the first place. What are you trying to accomplish here?
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