Hello all, I have the following problem and I don't see the error or I don't know what I'm doing wrong that it doesn't work. I have an Ubuntu 20.04 server with two IP addresses here in the example with 192.168.1.77 and 192.168.1.78 and I want to redirect the TCP. Port 23 from IP 192.168.1.78 to port 2323 additionally because the service behind it listens primarily on 2323. Below in the config examples I have two different variants of /etc/ufw/before.rules in the *nat section therefore variant 1 and variant 2 I hope someone can help me with my problem, also I don't see any smart information in /var/log/syslog nor in /var/log/ufw.log indicating a problem. root@adu4d4:~# cat /etc/netplan/00-installer-config.yaml # This is the network config written by 'subiquity' network: ethernets: enp0s3: addresses: [192.168.1.77/24, 192.168.1.78/24] gateway4: 192.168.1.1 nameservers: addresses: - 192.168.1.1 search: - fritz.box version: 2 root@adu4d4:~# ---------------------------------------------------------------------------------- root@adu4d4:~# cat /etc/sysctl.conf |grep forward # Uncomment the next line to enable packet forwarding for IPv4 net.ipv4.ip_forward=1 # Uncomment the next line to enable packet forwarding for IPv6 #net.ipv6.conf.all.forwarding=1 root@adu4d4:~# ---------------------------------------------------------------------------------- Variante 1 root@adu4d4:~# cat /etc/ufw/before.rules # # rules.before # # Rules that should be run before the ufw command line added rules. Custom # rules should be added to one of these chains: # ufw-before-input # ufw-before-output # ufw-before-forward # *nat REROUTING ACCEPT [0:0] -A PREROUTING -d 192.168.1.78 -p tcp --dport 23 -j REDIRECT --to-port 2323 COMMIT # Don't delete these required lines, otherwise there will be errors *filter :ufw-before-input - [0:0] :ufw-before-output - [0:0] :ufw-before-forward - [0:0] :ufw-not-local - [0:0] # End required lines # allow all on loopback -A ufw-before-input -i lo -j ACCEPT -A ufw-before-output -o lo -j ACCEPT # quickly process packets for which we already have a connection -A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT # drop INVALID packets (logs these in loglevel medium and higher) -A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny -A ufw-before-input -m conntrack --ctstate INVALID -j DROP # ok icmp codes for INPUT -A ufw-before-input -p icmp --icmp-type destination-unreachable -j ACCEPT -A ufw-before-input -p icmp --icmp-type time-exceeded -j ACCEPT -A ufw-before-input -p icmp --icmp-type parameter-problem -j ACCEPT -A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT # ok icmp code for FORWARD -A ufw-before-forward -p icmp --icmp-type destination-unreachable -j ACCEPT -A ufw-before-forward -p icmp --icmp-type time-exceeded -j ACCEPT -A ufw-before-forward -p icmp --icmp-type parameter-problem -j ACCEPT -A ufw-before-forward -p icmp --icmp-type echo-request -j ACCEPT # allow dhcp client to work -A ufw-before-input -p udp --sport 67 --dport 68 -j ACCEPT # # ufw-not-local # -A ufw-before-input -j ufw-not-local # if LOCAL, RETURN -A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN # if MULTICAST, RETURN -A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN # if BROADCAST, RETURN -A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN # all other non-local packets are dropped -A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny -A ufw-not-local -j DROP # allow MULTICAST mDNS for service discovery (be sure the MULTICAST line above # is uncommented) -A ufw-before-input -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT # allow MULTICAST UPnP for service discovery (be sure the MULTICAST line above # is uncommented) -A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT # don't delete the 'COMMIT' line or these rules won't be processed COMMIT root@adu4d4:~# ---------------------------------------------------------------------------------- Variante 2 root@adu4d4:~# cat /etc/ufw/before.rules # # rules.before # # Rules that should be run before the ufw command line added rules. Custom # rules should be added to one of these chains: # ufw-before-input # ufw-before-output # ufw-before-forward # *nat REROUTING ACCEPT [0:0] -A PREROUTING -d 192.168.1.78 -p tcp --dport 23 -j DNAT --to-destination 192.168.1.78:2323 COMMIT # Don't delete these required lines, otherwise there will be errors *filter :ufw-before-input - [0:0] :ufw-before-output - [0:0] :ufw-before-forward - [0:0] :ufw-not-local - [0:0] # End required lines # allow all on loopback -A ufw-before-input -i lo -j ACCEPT -A ufw-before-output -o lo -j ACCEPT # quickly process packets for which we already have a connection -A ufw-before-input -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A ufw-before-output -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT -A ufw-before-forward -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT # drop INVALID packets (logs these in loglevel medium and higher) -A ufw-before-input -m conntrack --ctstate INVALID -j ufw-logging-deny -A ufw-before-input -m conntrack --ctstate INVALID -j DROP # ok icmp codes for INPUT -A ufw-before-input -p icmp --icmp-type destination-unreachable -j ACCEPT -A ufw-before-input -p icmp --icmp-type time-exceeded -j ACCEPT -A ufw-before-input -p icmp --icmp-type parameter-problem -j ACCEPT -A ufw-before-input -p icmp --icmp-type echo-request -j ACCEPT # ok icmp code for FORWARD -A ufw-before-forward -p icmp --icmp-type destination-unreachable -j ACCEPT -A ufw-before-forward -p icmp --icmp-type time-exceeded -j ACCEPT -A ufw-before-forward -p icmp --icmp-type parameter-problem -j ACCEPT -A ufw-before-forward -p icmp --icmp-type echo-request -j ACCEPT # allow dhcp client to work -A ufw-before-input -p udp --sport 67 --dport 68 -j ACCEPT # # ufw-not-local # -A ufw-before-input -j ufw-not-local # if LOCAL, RETURN -A ufw-not-local -m addrtype --dst-type LOCAL -j RETURN # if MULTICAST, RETURN -A ufw-not-local -m addrtype --dst-type MULTICAST -j RETURN # if BROADCAST, RETURN -A ufw-not-local -m addrtype --dst-type BROADCAST -j RETURN # all other non-local packets are dropped -A ufw-not-local -m limit --limit 3/min --limit-burst 10 -j ufw-logging-deny -A ufw-not-local -j DROP # allow MULTICAST mDNS for service discovery (be sure the MULTICAST line above # is uncommented) -A ufw-before-input -p udp -d 224.0.0.251 --dport 5353 -j ACCEPT # allow MULTICAST UPnP for service discovery (be sure the MULTICAST line above # is uncommented) -A ufw-before-input -p udp -d 239.255.255.250 --dport 1900 -j ACCEPT # don't delete the 'COMMIT' line or these rules won't be processed COMMIT root@adu4d4:~# ---------------------------------------------------------------------------------- root@adu4d4:~# cat /etc/ufw/user.rules *filter :ufw-user-input - [0:0] :ufw-user-output - [0:0] :ufw-user-forward - [0:0] :ufw-before-logging-input - [0:0] :ufw-before-logging-output - [0:0] :ufw-before-logging-forward - [0:0] :ufw-user-logging-input - [0:0] :ufw-user-logging-output - [0:0] :ufw-user-logging-forward - [0:0] :ufw-after-logging-input - [0:0] :ufw-after-logging-output - [0:0] :ufw-after-logging-forward - [0:0] :ufw-logging-deny - [0:0] :ufw-logging-allow - [0:0] :ufw-user-limit - [0:0] :ufw-user-limit-accept - [0:0] ### RULES ### ### tuple ### allow tcp 22 192.168.1.77 any 0.0.0.0/0 in -A ufw-user-input -p tcp -d 192.168.1.77 --dport 22 -j ACCEPT ### tuple ### allow tcp 23 192.168.1.78 any 0.0.0.0/0 in -A ufw-user-input -p tcp -d 192.168.1.78 --dport 23 -j ACCEPT ### tuple ### allow tcp 2323 192.168.1.78 any 0.0.0.0/0 in -A ufw-user-input -p tcp -d 192.168.1.78 --dport 2323 -j ACCEPT ### END RULES ### ### LOGGING ### -A ufw-after-logging-input -j LOG --log-prefix "[UFW BLOCK] " -m limit --limit 3/min --limit-burst 10 -I ufw-logging-deny -m conntrack --ctstate INVALID -j RETURN -m limit --limit 3/min --limit-burst 10 -A ufw-logging-deny -j LOG --log-prefix "[UFW BLOCK] " -m limit --limit 3/min --limit-burst 10 -A ufw-logging-allow -j LOG --log-prefix "[UFW ALLOW] " -m limit --limit 3/min --limit-burst 10 ### END LOGGING ### ### RATE LIMITING ### -A ufw-user-limit -m limit --limit 3/minute -j LOG --log-prefix "[UFW LIMIT BLOCK] " -A ufw-user-limit -j REJECT -A ufw-user-limit-accept -j ACCEPT ### END RATE LIMITING ### COMMIT root@adu4d4:~# ---------------------------------------------------------------------------------- root@adu4d4:~# cat /etc/default/ufw # /etc/default/ufw # # Set to yes to apply rules to support IPv6 (no means only IPv6 on loopback # accepted). You will need to 'disable' and then 'enable' the firewall for # the changes to take affect. IPV6=yes # Set the default input policy to ACCEPT, DROP, or REJECT. Please note that if # you change this you will most likely want to adjust your rules. DEFAULT_INPUT_POLICY="DROP" # Set the default output policy to ACCEPT, DROP, or REJECT. Please note that if # you change this you will most likely want to adjust your rules. DEFAULT_OUTPUT_POLICY="ACCEPT" # Set the default forward policy to ACCEPT, DROP or REJECT. Please note that # if you change this you will most likely want to adjust your rules DEFAULT_FORWARD_POLICY="ACCEPT" # Set the default application policy to ACCEPT, DROP, REJECT or SKIP. Please # note that setting this to ACCEPT may be a security risk. See 'man ufw' for # details DEFAULT_APPLICATION_POLICY="SKIP" # By default, ufw only touches its own chains. Set this to 'yes' to have ufw # manage the built-in chains too. Warning: setting this to 'yes' will break # non-ufw managed firewall rules MANAGE_BUILTINS=no # # IPT backend # # only enable if using iptables backend IPT_SYSCTL=/etc/ufw/sysctl.conf # Extra connection tracking modules to load. IPT_MODULES should typically be # empty for new installations and modules added only as needed. See # 'CONNECTION HELPERS' from 'man ufw-framework' for details. Complete list can # be found in net/netfilter/Kconfig of your kernel source. Some common modules: # nf_conntrack_irc, nf_nat_irc: DCC (Direct Client to Client) support # nf_conntrack_netbios_ns: NetBIOS (samba) client support # nf_conntrack_pptp, nf_nat_pptp: PPTP over stateful firewall/NAT # nf_conntrack_ftp, nf_nat_ftp: active FTP support # nf_conntrack_tftp, nf_nat_tftp: TFTP support (server side) # nf_conntrack_sane: sane support IPT_MODULES="" root@adu4d4:~# ---------------------------------------------------------------------------------- root@adu4d4:~# netstat -na |more Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 192.168.1.78:2323 0.0.0.0:* LISTEN tcp 0 0 192.168.1.78:53 0.0.0.0:* LISTEN tcp 0 0 192.168.1.77:53 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:53 0.0.0.0:* LISTEN tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN tcp 0 0 192.168.1.77:22 0.0.0.0:* LISTEN tcp 0 0 192.168.1.77:25 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN tcp 0 0 127.0.0.1:953 0.0.0.0:* LISTEN tcp 0 0 192.168.1.77:22 192.168.1.141:62064 ESTABLISHED tcp6 0 0 fe80::a00:27ff:fe5e::53 :::* LISTEN tcp6 0 0 ::1:53 :::* LISTEN tcp6 0 0 ::1:953 :::* LISTEN udp 0 0 127.0.0.1:40427 127.0.0.53:53 ESTABLISHED udp 0 0 192.168.1.78:53 0.0.0.0:* udp 0 0 192.168.1.78:53 0.0.0.0:* udp 0 0 192.168.1.78:53 0.0.0.0:* udp 0 0 192.168.1.78:53 0.0.0.0:* udp 0 0 192.168.1.77:53 0.0.0.0:* udp 0 0 192.168.1.77:53 0.0.0.0:* udp 0 0 192.168.1.77:53 0.0.0.0:* udp 0 0 192.168.1.77:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* udp 0 0 127.0.0.1:53 0.0.0.0:* udp 0 0 127.0.0.53:53 0.0.0.0:* udp6 0 0 ::1:53 :::* udp6 0 0 ::1:53 :::* udp6 0 0 ::1:53 :::* udp6 0 0 ::1:53 :::* udp6 0 0 fe80::a00:27ff:fe5e::53 :::* udp6 0 0 fe80::a00:27ff:fe5e::53 :::* udp6 0 0 fe80::a00:27ff:fe5e::53 :::* udp6 0 0 fe80::a00:27ff:fe5e::53 :::* raw6 0 0 :::58 :::* 7 Active UNIX domain sockets (servers and established) Thanks for helping and best regards Alisha Manuela
