Fabric APIv4, Connection to azure, Technical background vlanSTag in zSide

Hi dirkf !

The reference in the migration from v3 to v4 documentation looks to have a typo. Instead of vlanSTag , this should be vlanCTag . Will flag this so we can get this corrected! Referring specifically the subsection "Redundant connections to Microsoft Azure ExpressRoute from DOT1Q ports" .

The linkProtocol object containing the vlanCTag property on the zSide is optional.

                    "linkProtocol": {
                        "type": "QINQ",
                        "vlanCTag": 2002
                    },

• If users provide the linkProtocol object containing the vlanCTag property as part of the connection request,  Fabric will use this cTag value to configure as the inner tag on the Azure (zSide) port. This automatically provisions the network on Fabric once the request is received. Users would have ensure to use the same cTag (VLAN) value when they configure the peering settings on Azure.
• If users do not provide the linkProtocol object containing the vlanCTag as part of the connection request, then Fabric does not automatically provision the network, as it does not yet have an inner tag to configure on the Azure-facing (zSide) port. In this case users can configure any cTag (VLAN) value on the peering settings on Azure, which will get "synced back" to Fabric and then subsequently provisioned.

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dirkf wrote:

Specifically: Can we always use the same VLAN ID in connections to different Azure environments when using unique VLAN IDs on the aSide?
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Whether you provide the vlanCTagvalue as part of the Fabric connection provisioning, or through the Azure peering configuration, the recommendation would be to use unique zSide VLAN IDs (cTags) for every pair of redundant connections to avoid any potential VLAN overlap on the Azure side of the connection. 

e.g.:
Redundant connection pair #1:
Primary connection (zSide VLAN/cTag = 100)
Secondary connection (zSide VLAN/cTag = 100)

Redundant connection pair #2:
Primary connection (zSide VLAN/cTag = 200)
Secondary connection (zSide VLAN/cTag = 200)

 

Azure peering configuration screenshot:

Hope this helps!
/David