Hello, I have these rules working:
iptables -A PREROUTING -d 195.116.19.244/32 -p tcp -m tcp --dport 21 -j DNAT --to-destination 192.168.1.2:21
iptables -A POSTROUTING -s 192.168.1.0/24 -d 192.168.1.0/24 -p tcp -m tcp --dport 21 -j SNAT --to-source 192.168.1.1
I need the kmod-nf-bridge module for other rules to work and enabled net.bridge.bridge-nf-call-iptables=1.
The problem is, ftp connection is NOT working anymore on the "target" server 192.168.1.2 when doing a nc -zv 195.116.19.244 21. Doing this on the other host of my LAN works! I guess it's because i am checking from the same switch interface. I see DNAT traffic comming in on my router, but nothing in SNAT.
So how can i workaround this?
PS: On switch port LAN1 i have a bridge br0. Thus i have 2 hosts here. Can NAT work based on MACs?
[Fri May 27 16:42:41 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:52:54:00:37:c4:df:08:00 SRC=192.168.1.2 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31084 DF PROTO=TCP SPT=48182 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:41 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:96:1d:a4:65:15:60:08:00 SRC=192.168.1.4 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=36666 DF PROTO=TCP SPT=41672 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:42 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:52:54:00:37:c4:df:08:00 SRC=192.168.1.2 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31085 DF PROTO=TCP SPT=48182 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:44 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:52:54:00:37:c4:df:08:00 SRC=192.168.1.2 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31086 DF PROTO=TCP SPT=48182 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:48 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:52:54:00:37:c4:df:08:00 SRC=192.168.1.2 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31087 DF PROTO=TCP SPT=48182 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:49 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:96:1d:a4:65:15:60:08:00 SRC=192.168.1.4 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=36667 DF PROTO=TCP SPT=41672 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:42:57 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:52:54:00:37:c4:df:08:00 SRC=192.168.1.2 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=31088 DF PROTO=TCP SPT=48182 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0
[Fri May 27 16:43:07 2022] NAT_PRER: IN=br-lan OUT= PHYSIN=lan1 MAC=84:a4:23:09:5f:86:96:1d:a4:65:15:60:08:00 SRC=192.168.1.4 DST=195.116.19.244 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=36668 DF PROTO=TCP SPT=41672 DPT=21 WINDOW=64240 RES=0x00 SYN URGP=0