Hi guys,
Set up a droplet having the private networking option enabled. My aim is to:
- Keep internet available on the droplet (so killing eth0 interface is not an option).
- Block all incoming traffic from the internet.
- Communicate with the droplet using the private IP (from another droplet).
I tried both these iptables (flipped order between two options), to absolutely no avail:
:INPUT ACCEPT [3:180]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [255:30170]
-A FORWARD -i eth0 -j DROP
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
COMMIT
and
:INPUT ACCEPT [3:180]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [255:30170]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A FORWARD -i eth0 -j DROP
COMMIT
Testing the changes this way:
Go on another droplet, and ssh using both of these:
ssh username@targetpublicip
and
ssh username@targetprivateip
In both cases, both keep working fine.
When I tried just this in the iptables:
iptables -I INPUT -i eth0 -j DROP
I couldn’t SSH using the private IP either.
I’m using the ams2 datacentre for both droplets.
Thanks and regards
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First clear the existing iptables rules by running these commands
iptables -F
iptables -X
After you clean you can view the rules with
iptables -L
Then run in terminal the following rules
iptables -P INPUT DROP
iptables -P FORWARD DROP
iptables -P OUTPUT DROP
allow loopback device, some software requires it
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT
allow ssh connection
iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT
iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
replace x.x.x.x with the droplet ip you want to allow connections with, this is for ipv4
iptables -A INPUT -s x.x.x.x -j ACCEPT
iptables -A OUTPUT -d x.x.x.x -j ACCEPT
Note: Save the iptables rules before restarting your droplet so they don’t get lost
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