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New Member

3560

Hi there!

I?ve got the following doubt.I want to create a L2 vlan between two 3560?s. The two swithces are in different buildings and are coneccted to the fiber optical MAN of the city.I have setup a trunk connection in both swithches and the connectivity is perfect at L3 ( 100mb ) . Now we want to creat a L2 vlan and also test the conectivity,to do this we connect to pc?s at each end and plug in the rj-45 connector to the port of the switch that has the L2 vlan applied but the switches just adds the mac address to its mac-address-table and doesnt share this table with the other switch. How can i make so that they share the mac-address-table through the trunk port??? This L2 Vlan is allowed already on the trunk port. Do i need to configure some type of gateway on the Layer 2 vlan or access port to redirect traffic to the trunk port ??

Thanks,

5 REPLIES

Re: 3560

Now we want to creat a L2 vlan and also test the conectivity,to do this we connect to pc?s at each end and plug in the rj-45 connector to the port of the switch that has the L2 vlan applied but the switches just adds the mac address to its mac-address-table and doesnt share this table with the other switch. How can i make so that they share the mac-address-table through the trunk port???

>>>Mac-address table is not shared between switches. Switches LEARN the mac-address and in order to learn a mac-address and the switch build a mac-address-table from this learned mac-address, the PC or host has to send a traffic/packet. Your switch is not learning a mac-address of the host connected to the other switch because it's not sending a traffic that traverses the trunk port. Ping from a PC1 that is in say vlan 2 in building A and ping another PC2 in vlan 2 in Building B and this should put the mac-address of PC2 in the trunk port of the switch in building A.

This L2 Vlan is allowed already on the trunk port. Do i need to configure some type of gateway on the Layer 2 vlan or access port to redirect traffic to the trunk port ??

>> simply allowing a vlan will not cause the switch to built a mac-address, as indicated above the host or PC have to send a packet in order for the switch to learn the mac-address of that host. Switch is a learning switch, it builds it's CAM table through source mac-address of the host/devices that send the packet.

Follow the following and if there is connectivity between the two swtiches at layer 2, I assure that you see mac-address of both PC in the trunk port of both switches:

1. connect a PC1 in fa 0/1 in switch A (lets say it's in building A)

2. assign fa 0/1 in vlan 2

3. connect a PC1 in fa 0/1 in switch B (this one is the switch in another building, let's say building B)

4. amke sure that both switch are in the same subnet, for the sake of this test assign PC1 with an IP address of 192.168.1.1 255.255.255.0 and PC with 192.168.1.2 255.255.255.0

5. If you ping from PC1 to PC2, you should see the mac-address of PC2 in switch A's mac-address-table and PC1's mac-address in switch B's mac-address-table.

I hope this little test does not muddy the concept of how the switches learned mac-addresses, it has nothing to do with ping, it's just part of the test to prove a point.

Please rate helpful posts.

New Member

Re: 3560

One question,what do you mean with , "make sure both switches are in the same subnet" the only logical conection for this vlan is the trunk line between switches, and as we said before the L2 Vlan is not going to have an ip address and all the traffic has to travel at layer 2. Do you mean an ip addressing on any other interface of the switches..?

This test has been done, but only each switch learns the mac address of the host that has directly connected, we used that ip addressing 192.168.1.1 and 192.168.1.2 and tried to ping but with no success. So we assume that the ping comand is not travelling trough the trunk port yet :(

Re: 3560

I meant the two vlans are in the same subnet. If you can't ping between the two PC/host that are in the same vlan and same subnet, that means the trunk is not working. How are you verifying the trunk is up and running? Can you post the following from the two switches?

show cdp neigh detail

show run

show int trunk

show vlan

show int fa x/x switch >> for both of the ports connected to the hosts/PCS.

so, no ping, no packet is going through and therefore no mac address is learned.

Please rate helpful posts.

New Member

Re: 3560

The Layer 2 Vlan for the purpose is named Vlan 1696

New Member

Re: 3560

We have discovered the solution.It was not on the configuration of the switches,it was a cabling mistake. The L2 vlan was configured to travel across the other fiber, i told you there were two fiber access on each building, so we changed the fiber from one media-converter to the other one and now the host have ping conectivity.

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