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New Member

weird issue on "LAN extension"

Hey, guys

Today ran into a weird issue on LAN extension between 2 356 switches. My understanding of the LAN extension is just a QinQ metro Ethernet on fibre.

We have a office in another city close by and all the servers are hosted in our office. I have 2 vlans (111 and 200) configured to send over the fibre. It is just normal trunking, nothing fancy. I can ping from one end to the other on vlan 111 all the time; I can also ping from one end to the other end on vlan 200 but not all the time. I would need to reset the trunk interface on either Switch if i could not ping on vlan200 over fibre. I can see the arp entries on both switches for device on vlan 200 even ping stops working though.

I called ISP and the guy said nothing is wrong on their network. If circuit works for one vlan, it will also work for the other. I could agree with him but I still think there is something dropping packets, otherwise how can it suddenly lost connection and reset interface fixed issue?

Any suggestion? Please advise.

VIP Super Bronze

weird issue on "LAN extension"


Do you have additional fiber port in your switches?  If yes, try a different fiber port with the same config and test again.


New Member

weird issue on "LAN extension"

Sorry, I might confused you.

There are 2 ISP devices (also cisco switches) connected behind their fibre converter. I connect our switch to the ISP switch and then to the fibre convertor to ISP network.

So it will be something like:

My LAN<->local 3560<->ISP edge switch<->fibre convertor<-ISP FIBRE NETWORK->fibre convertor<->ISP edge switch<->remote 3560<->my remote LAN.

New Member

weird issue on "LAN extension"

No one ever run into similiar issue?

Still waiting...