The AWS Direct Connect service is widely used for configuring hybrid cloud environments. Let's discuss some of the most common issues with AWS Direct Connect:

• If you are unable to ping the Amazon peer IP address, check if the IP address is correctly configured and is in the proper VLAN. Also in the ARP table, check that the router has a MAC address of the AWS endpoint.
• If there are any intermediate devices in between, check that they have VLAN trunking enabled for the 802.1Q VLAN tag.
• Its always a good idea to flush the ARP table cache before testing connectivity issues.
• If you are able to ping the AWS peer IP address, but the virtual interface seems down, check if the BGP ASN and AWS ASN are correctly configured.
• You can also check the MDG authentication keys. They should match the keys in the downloaded router configuration files. 
• Check that there are no firewall or ACL rules that are blocking port 179 or any other higher ports, as these ports are required for BGP to establish a TCP connection.
• The router must also be configured to have a route for the private cloud network prefix over the BGP session. For a private virtual interface, use a private or public prefix, however, for a public virtual interface, you must use a publicly routable network prefix.

Lets now look at some common issues with the EC2 service, which is widely used by cloud applications.