I had an existing 2-networks, connected in a single connection to the core switch through the ISP DEMARC,
The 2- network was connected to the Core SW through the single node.
The 2-networks was communicated through the layer 2, each Sw has his own vlan
The 2- networks was connected through a single connection at the end (L2 connection)
The 2-networks was connected without any communication between them.
The plan was to made the 2-networks as a one network connected to the core sw with a single MPLS connection
The future was to create a second MPLS connection to the core SW.
When trying to make the 2-networks as a one network, it was creating a loop layer 2 and vlan flapping.
Is there any advice please??
With the attached pic a brief map drawing
What is this ISP Cloud? Is this a same router? Since you have mentioned you are using different VLAN for each network at each side of your demarcation point, are you using two different SVIs configured on both switches with different Subnets?
I can see there is layer two link between these two networks and you must be using that link as a trunk link, are you allowing the same VLAN which is being used as SVI on your layer 3 switches on that layer two link as well? Since connection to same node on service provider router must be leaking a default route to each side of the network, what default gateway are you using on downstream switches?
I think you need to give more information if my understanding is not right.
according to the updated drawing that I have attached, you will fine that SW-1, Sw-2 & sw-3 were communicated through for example vlan 10.
sw-1 was communicated to the other switches in different vlans( for each switch L2 had his own vlan and his own sub net), all the switches L2 were configured as an ip default gateway (VALN_X) to SW-1, the communication was a layer 2
the same situation with the SW-3, all the switches L2 was communicating was layer 2.
I tried to mad the Network 1 & 2 as a one network but I faced another issue was LOOP layer 2 to the SW-3,
so what I did
SW-1 TO SW-2 had vlan 100
SW-1 to SW-3 had vlan 10
so I fixed the loop layer2
create management vlan 300, in all network 1 and network 2
any advice ?