[NTLUG:Discuss] routing concept

[Leroy Tennison]

terry wrote:
> On Fri, Feb 29, 2008 at 4:03 PM, Richard <ntlug at rain4us.net> wrote:
>> I'm struggling with a routing concept and I'm wondering what the best
>> way to implement this would be.
>>
>> I have an internet connection that has been assigned a SINGLE ip address
>> with a class C addreses.   Then I have a /29 subnet being routed TO that
>> single ip address on the class C subnet.
>>
>> I understand TCPIP routing, but for some reason I just can't put 2+2
>> together in this case.  I have no idea how I'm supposed to bind and
>> route these IP addresses.  Do just bind the ip addresses of the routed
>> subnet onto the same interface through which the subnet will route???
>>
>> Oh...and I'm using iproute2 extensively on this box to do some
>> dead-gateway-detection between two different internet connections.
>>
>> --
>> Richard
>>
> 
> You need to give a little more detail or explain in a different way
> for  us to understand more clearly.
> 
> If you plan to use no servers at this time and only need one outside
> IP [for now], just set up on  one IP and use the default gw route and
> your done.
> 
> But if what you are saying is that you have a block of outside IPs and
> you need to use them, just set up your machine with one of the
> designated IPs and use alias's for the others.
> 
> If you plan to use a router, set up the asias's on the router and have
> it allow certailn inside IPs to use the outside IPs as needed.  In
> other words set the router to allow your various inside host IPs to
> use outside IPs as needed.
> 
> If  you are building your own router and want an easy go of it, try
> IPCop    See:  ipcop.org
> With an IPCop router, you simply set up an alias and then go to Port
> Forwarding and have a particular inside IP use that outside alais IP
> and forward ports as needed.
> 
> 
> 
Terry has alluded to an issue I was going to raise, are the /29 (inside 
network) registered Internet addresses or are they something someone 
just picked?  The reason I ask is that, unless they are 
Internet-registered addresses, you are going to need to do Network 
Address Translation (NAT).  If I understand you correctly your 
Internet-facing host has only one IP address facing the Internet.  In 
that situation if you are going to do NATing then you have one choice: 
port translation.  The routing hosts replaces the original IP address 
with it's own and assigns a unique port to the outbound packet.  It 
keeps it's own table of the relationships to enable the communication.