A user has configured ELB with two EBS backed EC2 instances. The user is trying to understand the DNS access and IP support for ELB. Which of the below mentioned statements may not help the user understand the IP mechanism supported by ELB?
A.
The client can connect over IPV4 or IPV6 using Dualstack
B.
ELB DNS supports both IPV4 and IPV6
C.
Communication between the load balancer and back-end instances is always through IPV4
D.
The ELB supports either IPV4 or IPV6 but not both
Suggested Answer:D🗳️
Elastic Load Balancing supports both Internet Protocol version 6 (IPv6. and Internet Protocol version 4 (IPv4.) Clients can connect to the user's load balancer using either IPv4 or IPv6 (in EC2-Classic. DNS. However, communication between the load balancer and its back-end instances uses only IPv4. The user can use the Dualstack-prefixed DNS name to enable IPv6 support for communications between the client and the load balancers. Thus, the clients are able to access the load balancer using either IPv4 or IPv6 as their individual connectivity needs dictate.
D
ELB DNS supports both IPV4 and IPV6 and we use Dualstack-prefixed DNS name to connect over IPV4 or IPV6
However, "communication between the load balancer and its back-end instances uses only IPv4".
in EC2-Classic. DNS. However, communication between the load balancer and its back-end instances uses only IPv4. But EC2-Classic LB Supports Both Ipv6/4 from client. So only underlying machines of ELB uses Ipv4.
The base public DNS name returns only IPv4 records. The public DNS name with the ipv6 prefix returns only IPv6 records. The public DNS name with the dualstack prefix returns both IPv4 and IPv6 records.
Although the Route53 console always prepends dualstack. to the DNS name when choosing an Alias Target for an A (IPv4) or AAAA (IPv6) Resource Record Set (as noted in the documentation), and additionally the dualstack.* endpoint always correctly returns an IPv4 A record, only the DNS names for an EC2-Classic ELB (either the dualstack.* or ipv6.* endpoint) currently return IPv6 AAAA records, or serve as a valid alias target for an AAAA record.
You can confirm using dig:
dig dualstack.[endpoint] A dualstack.[endpoint] AAAA +short
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