19. Allowing ICMP in Security list within same subnet(Self ‐Rule) - Ayushi-srivastav/OCI GitHub Wiki

Open 1st instance in a putty and run below command to know host's IP

hostname -i

Next open 2nd instance in a putty and run below command to know host's IP

hostname -i

Now, Try to ping one instance to another instance in same subnet

ping (host IP)

As we can see in below screen ,we are not able to connect/ping to one instance to another.

Go to console, click on burger menu and select VCN in Networking section

Scroll down and open the subnet (In which both instance are created)

Again scroll down and click on security list under Resources and open Default security list

Note : There are two rules in default security list. Ingress Rules & Egress Rules Ingress Rule is for incoming traffic and Egress is for outgoing traffic.

As we can see in the screen below, in the Ingress Rules, there are two rules added that do not allow incoming traffic from a particular IP series (the mentioned IP series is our VCN's IP). Because of this, we are unable to connect between the two instances.

So, we have to add a new rule here.

Open your Public/private subnet and copy IPv4 CIDR

Again open security list and click on add Ingress rule under Ingress rule

Paste the Subnet's copied IP,select protocol ICMP and create the rule

New rule is created.as this rule allowed to connect 2 instance in the same subnet.

As we can see here, we are now able to connect/ping between 2 instances in same subnet