[Question] With ikev2 only mode, is all the iptables rules required

[chiragrajk]

For context I am trying to setup vpn with ikev2 mode only on AWS EC2 Ubuntu instance. Are all iptables rules setup in vpnsetup_ubuntu.sh:578 required for ikev2 only mode?

[hwdsl2]

@chiragrajk Hello! For IKEv2 only mode, some IPTables rules are not required: 1. Rules related to UDP port 1701. 2. Rules related to "ppp+". 3. Rule containing "L2TP_NET". Removing them is not necessary for IKEv2 only mode to work, but you can if you want. Note that the IPTables commands are numbered, so you will need to update the rule numbers accordingly.

The relevant part of the script is:

setup-ipsec-vpn/vpnsetup_ubuntu.sh

Lines 576 to 614 in b7b3fc3

	update_iptables() {
	bigecho "Updating IPTables rules..."
	IPT_FILE=/etc/iptables.rules
	IPT_FILE2=/etc/iptables/rules.v4
	ipt_flag=0
	if ! grep -qs "hwdsl2 VPN script" "$IPT_FILE"; then
	ipt_flag=1
	fi
	ipi='iptables -I INPUT'
	ipf='iptables -I FORWARD'
	ipp='iptables -t nat -I POSTROUTING'
	res='RELATED,ESTABLISHED'
	if [ "$ipt_flag" = 1 ]; then
	service fail2ban stop >/dev/null 2>&1
	iptables-save > "$IPT_FILE.old-$SYS_DT"
	$ipi 1 -p udp --dport 1701 -m policy --dir in --pol none -j DROP
	$ipi 2 -m conntrack --ctstate INVALID -j DROP
	$ipi 3 -m conntrack --ctstate "$res" -j ACCEPT
	$ipi 4 -p udp -m multiport --dports 500,4500 -j ACCEPT
	$ipi 5 -p udp --dport 1701 -m policy --dir in --pol ipsec -j ACCEPT
	$ipi 6 -p udp --dport 1701 -j DROP
	$ipf 1 -m conntrack --ctstate INVALID -j DROP
	$ipf 2 -i "$NET_IFACE" -o ppp+ -m conntrack --ctstate "$res" -j ACCEPT
	$ipf 3 -i ppp+ -o "$NET_IFACE" -j ACCEPT
	$ipf 4 -i ppp+ -o ppp+ -j ACCEPT
	$ipf 5 -i "$NET_IFACE" -d "$XAUTH_NET" -m conntrack --ctstate "$res" -j ACCEPT
	$ipf 6 -s "$XAUTH_NET" -o "$NET_IFACE" -j ACCEPT
	$ipf 7 -s "$XAUTH_NET" -o ppp+ -j ACCEPT
	iptables -A FORWARD -j DROP
	$ipp -s "$XAUTH_NET" -o "$NET_IFACE" -m policy --dir out --pol none -j MASQUERADE
	$ipp -s "$L2TP_NET" -o "$NET_IFACE" -j MASQUERADE
	echo "# Modified by hwdsl2 VPN script" > "$IPT_FILE"
	iptables-save >> "$IPT_FILE"
	if [ -f "$IPT_FILE2" ]; then
	conf_bk "$IPT_FILE2"
	/bin/cp -f "$IPT_FILE" "$IPT_FILE2"
	fi
	fi
	}