atcomsystems.ca/forum Forums VOIP Phones & IP PBX Networking TCP protocol

Okay I am not a networking guy, but use some with Mitel programming (and gaining IP access to programming remotely) so I hope someone will have a little patience in explaining some things to me.

At a property that has an group of static IPs and one is available I like to set up a basic router that I can port forward 2000 to the Mitel which will get me to programming via telnet or browser. The WAN port of the router is programmed with the Static IP and the LAN port is programmed with the gateway address of the Mitel. (I have this working in a couple of locations).

Problem is that I am working with a guy on a couple of installs (I am doing the remote PBX programming) and he INSISTS that programming the static IP on the WAN port of the PBX dedicated router is not enough. He says that the ISP has to assign a specific IP to a specific LAN port on their modem and that's what MY router has to plug into.

Well that didn't make any sense to me so I did a little research and from what I can understand when an IP address is entered in a browser or in telnet client it basically sets up a "broadcast' that waits for an answer so it knows where to route the packets. So if the router with the static IP dedicated to the PBX has it's WAN port programmed with the static IP it will answer that call and the info will be routed there.

It is also my understanding that if you have an ISP modem with only a single LAN port on it - that can be connected to a dumb switch and then the PBX router can be plugged in there.

This guy I am working with installs some small WIFI systems and has some knowledge, but thinks he is a computer expert. Also he is a very "anal" guy who will refuse to listen to anyone.

So, if I am right I would appreciate someone explaining this in a way I can pass along that even he will understand.

Thanks for your help sorry if I was a little long winded and possibly unclear.

Dane

I can answer this on two levels. The first is the practical level. Don't try to educate or argue with the computer guy. Try to figure out his language and speak it. If he says up is down and down is sideways, just speak his language to him. Do you want to be right or do you want to make a living? Training is extra.

On the technical level: when you telnet or browse to an IP address, it is not broadcasted. Your packet is sent directly and only to the location of that IP address as known to the routers on the Internet. If every initial packet was broadcast across the Internet, there would not be room for much else.

What you need from the CG is this: assign the available Internet address to the outside interface of the router; have port 2000/tcp on the outside interface of the router forwarded to port 2000/tcp on your PBX. This is known as a virtual server.

By the way, you don't need to use a separate public Internet address just for your PBX. If the router already has a public Internet address, you can use the same Internet address to access your PBX. It will be at port 2000/tcp instead of port 80/tcp, which is the common address for a web server or port 23/tcp which is the common address for a telnet server.

Thanks - some of that I knew. However I have a question as to "how" the "internet" knows where a specific IP resides (if, as you say, it is sent only to the one specific IP address).

This guy is not really a "computer guy" )though that is what he fancies himself).

Not sure what you mean by the "outside" interface of the router - are you referring to the WAN side?

I have set up forwarding in routers. So I am familiar with that.

Usually in the situations that I deal with if they have one static IP they have multiples, but if they didn't I would assume that one would then have to program the modem/router on the ISP line.

Again, thanks and always happy to be educated.

The "internet" "knows" where a specific IP address resides because each router has a routing table that it uses to determine where to send each packet it receives, and because Internet routers share their routing table with each other using a routing protocol.

Your PC is a router. If you want to see the routing table in your computer, type "route print" at the comand line.

Since Grim missed it, yes the "outside" interface is typically the "WAN" side of your typical linksys/d-link/netgear/etc router. The more "correct" translation of the "outside" interface would be the interface that is using a public routable ip address.

I'm a little north of you but I might be able to help if you need me to.

IP addresses are assigned by the ISP using a subnet of a block of IP's that is then assigned to your circuit. How you use these IP's is based on the type of service you are getting. If it is a T1 then you will get a block of IP's and can connect the WAN port of the ISP's router to your network and then assign the IP's to devices (routers, firewalls, mail servers, camera's etc) on the network. If it is ADSL with PPOE then you will need to provide a router with a route table built in it to parse out the IP's as you will probably recieve them in a dynamic fashion from the ISP via their modem.

The far simpler solution is to use port forwarding with 1 static IP.

Thanks for all the help guys. Like I said I am somewhat of a neophyte when ti comes to this, but am way ahead of where I was a year ago and thanks to the info y'all have provided I am ahead of where I was This morning.

BTW - the guy I am working with is in the Rockies.

One additional to what Grim posted, and just for clarification.

When you type in a name, there is something called DNS (directory name service) which allows the computer to convert the name to an IP.

Each router doesn't need to know where every host is. Each router checks its' internal host table and if the router doesn't have the host listed it checks the next router upstream until it finds one that knows what the IP is for the name you are looking for. Once the IP is loacated and passed back to your computer for making the connection the local router also adds it to its own host table until it isn't used for a configurable amount of time at which point it is flushed.

If your remote site has a Fixed address from the provider, you can use that IP directly, and not have to worry about DNS failures when connecting.

If the remote site has Dynamic IP addressing, there are services which work with the remote site to get the new address and update a DNS entry with the new IP information. Those sites can be found by searching for "Dynamic DNS" providers. Some routers will also talk to these services without needing software loaded at the client site.