SR-DR Transit logical switch is mandatory for V2T "User defined topology migration" when NSX-V DLR is mapped to Tier-0 or Tier-1 Gateway.
Below are the list of all scenarios when SR-DR Transit logical switch is missing.
Issue:1
SR-DR Transit logical switch(TLS) is absent on Tier-0 Gateway
Validation Error Message:
“Can not proceed with migration: NSX-T TIER0 Policy Gateway(GW) <Tier-0 Gateway name> does not have SR-DR Transit Logical Switch(TLS). Please Make Sure TIER0 GW has SR-DR TLS before starting Edge Migration]”
=====================================================
Issue:2
SR-DR Transit logical switch(TLS) is absent on Tier-1 Gateway
Validation Error Message:
“Can not proceed with migration: NSX-T TIER1 Policy Gateway(GW) <Tier-1 Gateway name> does not have SR-DR Transit Logical Switch(TLS). Please Make Sure TIER1 GW has SR-DR TLS before starting Edge Migration]”
======================================================
Issue:3
Tier-1 Gateway is DR only and it is not connected to any Tier-0
Validation Error Message:
"Tier-1 Policy Gateway <Tier-1 Gateway name> only has DR and it is not connected to any Tier-0 GW. Tier-1 should have SR and DR both OR it should be connected to Tier-0 GW"
======================================================
Issue:4
Tier-1 Gateway is DR only. It is connected to a parent Tier-0 which does not have SR-DR TLS.
Validation Error Message:
"Parent NSX-T Tier-0 Policy Gateway(GW) <Parent Tier-0 Gateway name> does not have SR-DR Transit Logical Switch(TLS). Please Make Sure Parent Tier-0 which is connected to <Tier-1 Gateway name> Tier-1 GW has SR-DR TLS before starting Edge Migration"
======================================================
Solution for Issue:1
1.First check if Uplink is correctly created and realized(i.e. in Success state) on Tier-0 before starting "Define Topology" L3-L7 stage in BYOT.
2. For SR-DR Transit logical switch(TLS) creation on Tier-0 gateway, uplink should be present on Tier-0 gateway.
3. In BYOT, user also need to configure dynamic or static routing on the Tier-0 gateways towards the northbound routers based on his requirements. For dynamic routing user can choose to configure either BGP or OSPF, based on his NSX-V configuration. User need to manually configure this northbound routing. Please refer this link for more details - https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.2/migration/GUID-4856BC63-27CB-49CC-AFF5-5AF7C16C2610.html
======================================================
Solution for Issue:2
1. First check if Edge Cluster is assigned with Tier-1 gateway before "Define Topology" L3-L7 stage in BYOT
2. For SR-DR Transit logical switch(TLS) creation on Tier-1 gateway, Edge Cluster should be assigned to Tier-1 gateway. Also Tier-1 gateway should be correctly realized.
======================================================
Solution for Issue:3
1. Tier-1 Policy Gateway is DR only. It does not have SR. To fix this user can create SR on Tier-1 by assigning Edge Cluster to mentioned Tier-1 gateway.
2. If user wanted this Tier-1 as DR only, then connect this Tier-1 gateway to parent Tier-0 which has SR-DR Transit logical Switch. Uplink should be present on Tier-0 gateway for SR-DR Transit logical switch creation.
======================================================
Solution for Issue:4
1. Tier-1 Policy Gateway is DR only. It does not have SR. To fix this user can create SR on Tier-1 by assigning Edge Cluster to mentioned Tier-1 gateway.
2. If user wanted this Tier-1 as DR only, then connect this Tier-1 gateway to a parent Tier-0 which has SR-DR Transit logical Switch. Uplink should be present on Tier-0 gateway for SR-DR Transit logical switch creation.
======================================================
Before starting L3-L7 migration with BYOT topology please refer VMware document https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.2/migration/GUID-4856BC63-27CB-49CC-AFF5-5AF7C16C2610.html,
Detailed Official V2T BYOT Migration document is present at -> https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.2/migration/GUID-EA79E00C-0036-41C8-B87C-7960770B831A.html
V2T Migration Fails during the validation Phase.