Re: Please explain port forwarding..
From: Jim Watt (jimwatt_at_aol.no_way)
Date: 05/19/04
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Date: Wed, 19 May 2004 18:04:05 +0200
On Wed, 19 May 2004 17:31:25 +0100, "Paul H" <nospam@nospam.com>
wrote:
>
>"Leythos" <void@nowhere.com> wrote in message
>news:MPG.1b153213f1500f2f98a549@news-server.columbus.rr.com...
>> In article <3AJqc.19$kK3.9@newsfe6-win>, nospam@nospam.com says...
>> >
>> > "Leythos" <void@nowhere.com> wrote in message
>> > news:MPG.1b1529e9e252090b98a548@news-server.columbus.rr.com...
>> > > In article <F_Iqc.15$kK3.6@newsfe6-win>, nospam@nospam.com says...
>> > > > I have a NAT router with an SPI and several PCs on a peer network. I
>> > have a
>> > > > good understanding of networks but....
>> > > >
>> > > > I have never been able to get what is really happening with port
>> > forwarding.
>> > > > Even though I have usefully configured my router to forward ports, I
>> > don't
>> > > > *really* know what I am doing.
>> > > >
>> > > > So, If I configure my NAT router to forward port 10,000 to
>192.168.0.26
>> > on
>> > > > my network does that mean?....
>> > >
>> > > Forwarding, means that the port specified that arrives inbound on the
>> > > specified public IP address (in case you have more than one) will be
>> > > forwarded to the specified internal IP address - no filtering, just
>all
>> > > data on port X will be forwarded to that IP.
>> > >
>> > > So, assuming that you are using a simple NAT router on a DSL/Cable
>> > > connection with 1 public IP address:
>> > >
>> > > Forwarding -
>> > >
>> > > IP Address PORT Enable
>> > > 192.168.10.200 80 X
>> > > 192.168.10.200 443 X
>> > >
>> > > In the above example, all inbound traffic on your Public IP address
>for
>> > > ports 80/443 will be forwarded to the internal IP of 192.168.10.200.
>> > >
>> > > If you had more than 1 public IP and a router that handles it, you can
>> > > create rules that allow you to specify the public ip, port, internal
>ip,
>> > > port, and enable/disable.
>> >
>> > Thanks for your reply.
>> >
>> > So is port forwarding a security risk?
>> >
>> > If I understand you correctly, **any** packet arriving at my routers WAN
>> > address destined for port 10,000 will be forwarded straight on to
>> > 192.168.0.26.
>> >
>> > So would someone scanning my network see port 10,000 as open or closed?
>> >
>> > Or if there was a worm going around that tried to get in via port 10,000
>> > would it get straight through to 192.168.0.26?
>> >
>> > ..still confused.. :o/
>>
>> Any data sent to port 10000 will be forwarded directly to the internal
>> address - there is no filtering, nothing, it just goes directly to it.
>> it would be considered OPEN to anyone.
>>
>> So, if you opened port 1433/1434 (MS SQL PORTS) and forwarded them to
>> your MS SQL server, you would be compromised in a short time since there
>> are still many traces of the SQL Slammer worm running around.
>>
>> If you need port forwarding you need to secure the machine that is the
>> destination of the forward - meaning that if you were running a web
>> server behind the router, you had better have locked it down (based on
>> the Web Server OS vendor suggestions), be running a strong Anti-virus
>> package, and have changed all accounts/passwords so that they don't
>> match any accounts/passwords on your other machines.
>>
>> Port forwarding is not a security threat, it's a normal way of doing
>> business - a threat would be the unsecured machine that is the
>> destination of the port forwarding. The best rule is that if you don't
>> know what you are doing, if you don't know how to secure it, if you are
>> unsure in any way, don't forward.
>>
>> --
>> --
>> spamfree999@rrohio.com
>> (Remove 999 to reply to me)
>
>Thanks a million for this, the penny is starting to drop..;O)
>
>One more thing..
>
>A common reason for a home user to mess with port forwarding is for gaming.
>Given what I now understand, why should a gamer have to do this? I can
>understand why exchange or SQL server would need port forwarding but why
>would a game need this just for multiplayer purposes, especially if he is
>**not ** running a server just a workstation and wants to join in the online
>fun?
>
>Thanks, last question..(promise)
>
>:O)
Port mapping allows inward connections through the NAT.
So if a gamer needs to connect to your machine this allows
him to do so from outside. There is not restriction on the
outgoing connections from your network.
-- Jim Watt http://www.gibnet.com
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