why an upstream switch should allow storage appliance port traffic?

Appliance port traffic must be allowed on uptream switches in case of below scenario:-

1. If storage must be accessed outside of the UCS domain.
2. If storage and servers are located in different subnets.
3. If storage is configured in Active/Passive mode and both fabric interconnects require  communication to the same controller.

Shadow consumer EPG

Shadow consumer EPG is the consumer interface of an L4-L7 device places

ACI broder leaf - Important points

1. Any ACI leaf can be a border leaf. There is no limitation in the number of leaf switches that can be used as border leaves.
2. The border leaf can also be used to connect to compute, IP storage, and service appliances.
3. The border leaves are dedicated leaf switches that support only Layer 2 and Layer 3 out in an ACI fabric.

BGP peering supports in ACI

ACI supports the following connections for BGP peering:

1. eBGP peering over OSPF
2. iBGP peering over direct connection
3. eBGP peering over direct connection
4. iBGP peering over static route

External Layer 3 Outside connections types in ACI

Below are the connection types for Layer 3 connection in ACI:-

1. Layer 3 Routed Interface
2. Sub-interface with 802.1Q tagging
3. Switched Virtual Interface (SVI)

External Layer 3 Outside connection options in ACI.

ACI supports the following External Layer 3 Outside connection options:

1. Static Routing (supported for IPv4 and IPv6)

2. OSPFv2 for normal and NSSA areas (IPv4)

3. OSPFv3 for normal and NSSA areas (IPv6)

4. iBGP (IPv4 and IPv6)

5. eBGP (IPv4 and IPv6)

6. EIGRP (IPv4 and IPv6)

Important points about L3Outs in an ACI Fabric.

1. ACI fabric runs MP-BGP 
2. Security import subnets control the forwarding of packets into and out o L3Out connections(data planE. 
3. Route control subnets control the exchange of routing information(Prefixes) into and out of the fibric (control place)

OTV failure isolation functions

Below functions are provided by OTV to achieve failure isolation.

1. ARP optimization

2. Unknown unicast traffic suppression

3. Spanning tree isolation