Question

Cannot ping a secondary address assigned to a private interface in a VPC?

Created two droplets in a VPC and each gets a ‘eth1’ with a IP address in some subnet.

Add another address from the same subnet to ‘eth1’ on one droplet. I cannot ping that address from the second droplet.

I can see ARPs coming through for the DO assigned addresses.

Is there some filtering going on in between?


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Hi,

The solution you are going to apply seems to not be officially supported by DO. Accordingly to the DO’s doc, ‘VPCs do not support multicast or broadcast’ - https://www.digitalocean.com/docs/networking/vpc/ . However, your goal is still achievable. So, you added an IP address to the interface eth1 on (let’s call it) droplet1. To make it visible on droplet2 you need to update its ARP table. You can do that with arp command. On droplet2 execute:

sudo arp -v -i eth1 -s droplet1_added_ip droplet1_eth1_mac_address

e.g. sudo arp -v -i eth1 -s 192.168.10.10 ea:82:31:14:0a:fb

To display ARP table, execute arp command with no parameters.

Unfortunately, such solution needs updating droplet2’s ARP table, at least after its restarting. I am not sure if you would have to update it periodically as well. On some network devices static ARP entries are held just for few hours.