AWS ELB instances tied to ELB and ip addresses

The Amazon Elastic Load Balancer takes care of scaling out the number of underlying EC2 instances that make up the software virtual load balancer that is the Amazon ELB. However, you may want to determine the number of instances that are servicing your requests if you plan to scale out the number of users for a large promotion or for processing of a large number of users.  Determining the number of underlying instances is easy. You can simply use the host or dig commands using the ELB DNS name. There will be a minimum of one EC2 instance for each AZ that the ELB is servicing.

1. [ec2-user@ip-10-0-0-50 ~]$host ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com
ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com has address 50.112.140.192
ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com has address 50.112.183.144


2. [ec2-user@ip-10-0-0-50 ~]$ dig ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.17.rc1.28.amzn1 <<>> ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 813
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;ReachForceAutoScalingELB-1142887282.us-west-2.elb.amazonaws.com. IN A

;; ANSWER SECTION:
ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com. 30 IN A 50.112.183.144
ReachForceAutoScalingELB-1342887266.us-west-2.elb.amazonaws.com. 30 IN A 50.112.140.192

;; Query time: 1 msec
;; SERVER: 10.0.0.2#53(10.0.0.2)
;; WHEN: Fri Jun  6 12:31:34 2014
;; MSG SIZE  rcvd: 113