A question on networking

[satimis]

Hi folks,


I'm building a LAMP server on Ubuntu 6.05 drake amd64 running local IP 192.168.0.52 w/o ports forwarded to this IP address.

After finishing installing Postfix mails can be sent to Internet on the server. But it can't receive mails from Internet if w/o port 25 forwarded to its IP address. I can't figure out why it can send mails w/o port 25 forwarded but not the other way round. Please shed me some light. TIA


B.R.
satimis

[stiles]

It's just following your LAN's default gateway and your firewall is letting it out based on the connection originating from your LAN. At least that's my guess based on what information is given.

[satimis]

It's just following your LAN's default gateway and your firewall is letting it out based on the connection originating from your LAN. At least that's my guess based on what information is given.
Hi stiles,


Thanks for your advice.


Iptables is NOT running on the mail server under building.


$ sudo iptables -L
Password:
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination



The new mail server is behind the gateway controlled by a router. I have to forward port 25 to its local IP, 192.168.0.52, before it can receive mails.


I have only one public IP which is used by a working mail server. To test a new mail server, under building, I have to forward port 25 temporarily to its local IP. Is there a way to get around it? TIA


B.R.
satimis

[stiles]

The new mail server is behind the gateway controlled by a router. I have to forward port 25 to its local IP, 192.168.0.52, before it can receive mails.

This router is what is letting new lan based connections out. Your new mail server's routing table is what is sending the outgoing packets to the router as the default gateway.


I have only one public IP which is used by a working mail server. To test a new mail server, under building, I have to forward port 25 temporarily to its local IP. Is there a way to get around it? TIA


No but you can use an alternative port. 587 is most often used for a low port for SMTP auth (the live mail server may be using this too so be careful) or you could use an arbitrary high port just for testing purposes.