I don't know the first thing about setting up Echolink (I know what it is), but a google got me this... http://www.echolink.org/firewall_solutions.htm
AND I have been doing tech support on router port forwards for several years now, so I know this well. Here is a step by step guide with pictures:http://portforward.com/english/routers/port_forwarding/Linksys/WRT54G/Echolink.htm
Between the two, maybe you can get it... (the second link will be most helpful!)
To answer your question, you should be concerned about the IP address of the PC (the first one). The gateway is the address inside the router that your PC calls to say, 'Hey, connect me to the outside world, please.' The thing is, while I don't see that the echolink webpage says this, but you might need to make the IP address of your PC static. (Not the static IP from your internet provider that costs extra!) Because if you reboot your computer and the router assigns your PC a NEW IP address, you will have to go configure this all over again.
Since you are a ham and most like to know things, plus others may read this, let me give you an upgraded version of the 'customer rap' I give to explain to people what's going on.
Inside your router you have a NAT, a gateway and a DHCP... techie speak, but essentially it acts like a switchboard on an old company telephone system. When you turn on your computer, unless you have a STATIC LAN IP (a permanent extension number), your computer calls the switchboard (the DHCP part) and says, 'Hey I need an extention number so I can make and receive calls'. The DHCP assigns your computer a LAN IP address (the first one; usually something like 192.168.1.###). It also tells your computer what the GATEWAY IP address is (the operator to call to get outside number listings). Once your computer has all this information, it can start placing outgoing calls to the internet... it can also receive calls from other computers on your network (other in-house extensions) but NOT from OUTSIDE IP addresses...
You see, when your computer asks for a webpage, it calls up the GATEWAY in the router and says, "hey, will you get me the telephone number for www.whateveryouwant.com?
" The gateway obliges... Then your computer calls up the NAT (network address translator) which is like the actual switchboard operator with the plugs and wires (okay, so I'm old... I actually ran one of those switchboards... twice). Your PC says to the NAT, 'will you get call this number and ask for this information?' And the NAT places the call... In computer terms, it takes a while for the information to come back. But not to worry, the NAT operator wrote down your extension along with who you called. So when the information comes back, it looks up the number it came from and says, 'Oh, this guy called for that,' and it rings your extension, then gives you the information. Without this... You might ask for a webpage, and then have it show up on your wife's computer... see what I mean. (not really, but you get the idea)
The NAT talks to the rest of the internet using the WAN IP for it's 'telephone number' (metaphorically speaking... not your actual phone number). The rest of the internet all have their own numbers and that's how everyone in the world calls everyone else. BUT everyone in your house (on your network) is using this same number. So the DHCP assigns everyone in the house their own extension number, and then acts as the go between... the NAT keeps track of who in the house called who out in the world, so it keeps everything straight and the right info goes to the right place.
Now... This all works fine when YOU want something from out THERE. But what happens when someone out THERE wants to call you? Well, you give them your IP address... the one that your internet provider assigns you. They call your number and your router says, 'What? What do you want?' Well, the outside computer doesn't say 'give me extension so & so'. That wouldn't be safe and also wouldn't tell what they WANT... only WHO they want. So, there is additional information given when they call up: a PORT NUMBER.
When the NAT gets an incoming call, it has a port number. It looks up the port number in it's chart and says... 'Do I have anyone that requested to receive calls for this port?' Some ports are commonly defined... some are for e-mail, some web pages, etc. (Echolink uses 5188 & 5189... they are used in pairs) If it does not find anything in it's list for that port number, the NAT ignores the call... (a good one does... this IS the FIREWALL part of things) It doesn't know who is calling, doesn't show that anyone on the inside called them and has no instructions on anything to do when someone calls on this port. So it hangs up... could be a criminal... could be a telemarketer... not talking to them!
SO... what a PORT FORWARD does (the thing you are trying to do here) is tell the NAT what to do when a call comes in on the Echolink port. You are telling the NAT to send those calls to a specific PC in your house.
Application Start End Protocol IP Address Enable
Echolink 5198 5200 Both 192.168.1.# yes
The above says, if a call comes in on 5189 or 5199 with either protocol (let's skip that shall we?) send it to 192.168.1.# (the '#' is the number assigned to your PC) and if enable is checked, it will actually do it. (Uncheck it to turn off temporarily without deleting information) The router doesn't care what the application name is, that's just so you know what you did there 8 months ago.
So... with all that explained... you can see why you do NOT what your PC running echolink to change it's address... If the call comes in and it's looking for number '150' but the number of your PC has been changed to '153' then you will never get the call. SO... to set up a static IP on your PC, go here: http://portforward.com/networking/staticip.htm
If you have any questions, feel free to contact me through the e-mail on my QRZ.com page... I don't regularly check these forums, I just happened to see your post listed on the front page and checked it out.
Good luck & 73!
DISCLAIMER: I am not a computer doctor, nor do I play one on TV... your mileage may vary, batteries not included, no warranties assumed or implied, does not include tax title and license, all rights reserved, writer not responsible for damage due to errors, reader assumes all risk and as ALWAYS... other restrictions MAY APPLY.