On Wed, 08 May 2019 12:21:21 +1300, nospam.Vince.Coen@f1.n250.z2.binkp.net
(Vince Coen) declaimed the following:

>
>Is there a firewall of any type installed by default ?
>
 Not by default, but it is recommended to install/activate it for a
machine used as a server.
https://makezine.com/2017/09/07/secure-your-raspberry-pi-against-attackers/

>I have a BBS system used as a back up for my main systems on the pi but it is
>not rceiving
>incoming broadband polls. The pi i address has been changed to that of the
>main system so that
>the router is passing requests to it (I assume) but that is it.
>

 What do you mean by "poll"? To most of us "poll" means a periodic check
for activity ("polling loop" in code, for example). The closest user
network activity would be running PING.

 I'm presuming a character dropout, and "pi i address" was supposed to
be "pi ip address".

 Unless your internal nodes have static WAN IP addresses, changing the
LAN private IP address probably won't help -- it depends upon the router
configuration. Most routers are performing NAT translation (they maintain a
table of LAN IP/port#  WAN IP/port#, and change packet headers as they go
through the router). If the router passthrough scheme uses internal host
names, changing LAN IP addresses doesn't change the name, the router still
passes traffic to the address the name is associated with.

 NAT systems are an inherent firewall -- one has to specify external
port numbers from which connections will be accepted, and the internal host
to which they should be sent (normally the translation table gets populated
only by internal requests making connections to external addresses, and any
external packet coming in that does not have a mapping will be dropped).
Depending upon router, that internal host may be either a private LAN IP
address OR a hostname on the LAN -- on my U-verse router, the firewall -
NAT/Gaming page lists my RPi server by hostname and service/port. So... on
my router, even if the LAN IP address gets changed, the router still sends
incoming HTTP traffic to the RPi.


--
 Wulfraed                 Dennis Lee Bieber         AF6VN
 wlfraed@ix.netcom.com

--- SoupGate-Win32 v1.05