I am relocating to Jackson County, North Carolina within a week or two. The local cable company in the area is Mediacom.
I took my VOIP adapter (Voicepulse is the VOIP provider I am using) and connected it directly to the cablemodem. It got a DHCP address, which turned out to start with a 10 (yes, a private IP address). I asked the installer if that was normal. He told me that they normally provided addresses that start with 10 or 12 (but the 12 is being treated by Mediacom as a private IP address as well).
This presents some issues. The first is will my Cisco 831 router work right with a private IP address on the Internet gateway? Will I need to change any settings? I understand that private IP addresses might be blocked through a NAT gateway (which is why I'm asking this question).
The second is about telnetting into my Cisco router and targeting my Webserver. Is there any way to be sure that I can do this (I use a software utility called Dynamic DNS in conjunction with an online service called ZoneEdit to handle changes of my public IP address when the dynamic address changes)? Thus,
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is targeted to the public gateway address on the router and NAT is used to forward the request to the Webserver on my home network. Bringing up http://10.100.101.102 from another location isn't going to work.
Suggestions? Maybe there is someone here that uses Mediacom and has already solved these issues.
I'm trying to find out if I can get a public IP address from Mediacom. If not, I may look into getting DSL instead.
It looks as if Mediacom will not let you use your setup as a server as there is no way of routing traffic to a private address. They will be doing some form of NAT possibly using the same Public IP address for several customers on the cable feed.
This method seems pretty naff if you ask me so I would recomend moving to that DSL you are talking about.
Just to answer another of your questions. There is no problem using NAT between 2 different private IP address's the 831 does not itself know the difference between public and private but this will not help i/c traffic to a server on your home network. All it will enable you to do is link multiple PC's for outgoing connections such as surfing, newsgroups, email etc.
I'm going to have to give that serious consideration.
That sounds good. I was told that routers differentiate between public and private, but most especially core routers (they apparently don't pass them to keep someone from leaking one out on the Internet, or so one of my instructors said). So I wasn't sure.
After reading your message, I called Mediacom and asked them about the private versus public address thing.
They left me on the phone for quite some time. Finally, they insisted I had a 12 address and that it was a public address (that's not what the installer told me when he put it in). That wasn't what the phone gave me when I checked it at the residence. So, he gave me the current address. I accessed the http://###.###.###.### address and got the login prompt (much to my surprise). I logged in and it does appear to be my adapter at the house up in NC.
I asked him if I'd always have a public address. He assured me that I would.
I suspect that they reoptioned my account so I get a public address because I think they perceived that I'd ultimately cancel if they didn't. But, that's just my perception of what happened.
Just to clarify the Public/Private address scenario. It is not just your
831 that has no concept by default to these Public/Private addresses. Core routers don't know the difference either. It is a requirement of an ISP to block private IP addresses to keep them just that "Private". ISP's use ACL's (Route Maps)they call Martian lists to block them on the Internet.
Don't quote me on this but I think there is a BGP option that can automate this also on incomming adverts but it's been a while since my BGP course.
One last point for completeness and for interest (if you are that is), some usually smaller ISP's also use Private IP addresses for their Point-Point links. This is also valid as the destination address of through traffic is never pointing to them, they just route over them. This reduces wastage of the IPv4 address range that they have probably leased off a larger ISP/Telco.
I have just re-read the thread as I was concerned a Cableco should issue a private address in the first place.
Is it possible that the cableco modem isn't just a modem but a modem/router. What I am thinking is that since you haven't moved yet is that this modem/router??? is already performing NAT hence your VOIP phone only saw a private address. If this is the case you may want to check you can log into the modem/router to change settings such as port forwarding so that you can use your setup as a server as well as securing it (admin passwords/no WAN access to management etc.).
I see. I was under the impression that not allowing private IP addresses to get onto the Internet was hard coded into the operating systems of the Core routers. I guess I was mistaken.
I've never done anything with BGP, so I can't answer that.
I am interested. Always want to learn more about networking.
I can understand it for the small, dialup customers. But so many people are adding devices that must be administered from outside their own network (VOIP devices as one example) that I can see it becoming a problem with small home network users and even small businesses. I wouldn't accept any arrangement for business without a gateway public IP address, myself. I don't want one for my home network, but that's me. Those who only surf the Web and check email might not care.
I've used both Earthlink and Road Runner and I've always gotten a public IP address.
Possible, but I don't think so. Since I logged into the adapter, it is showing a DHCP 12 (public) address in the setup (I'm not refering to the address bar on my browser). If the unit still had a 10 (private) address, it would show that address.
We'll see. Thanks for the good wishes. Happy Moving is an oxymoron.
I am not talking about customer links here. When I state Point-Point links I mean the ISP's own internal links using Private addresses. This is not a problem like you may have experienced as there is no NAT here. This is hard to explain on a short thread but you can envisage this as part of the ISP's own Private network. Your traffic in or outbound would not be affected as your traffic is only being routed over these links. In it's simplist terms your traffic does not originate or terminate on them and would be unaffected i/c or o/g.
Sorry for the confussion.
I tottaly agree as per my earlier post that this would be unacceptable for customer links.
I was under the impression that your original diagnosis was from the VOIP phone on the LAN side hence the private IP address shown. i.e. NAT address????
When I was at the residence in NC, I dialed '*' four times to get to the IP setup command mode on the VOIP device. Then I dialed '110#' which returns (audibly over the telephone set that you have plugged into the VOIP device) the DHCP address that the unit got from the ISP. It was a 10 series (private) address. I was unable to get the phone to work at all. As I didn't have time to get into a big commotion with the cable provider, I decided to call them when I got back to SC.
When I did, we hemmed and hawed. That's when they told me that I was mistaken and that I had a 12 series (public address). I had understood from the installer who came to my NC residence that they treated 12s as private addresses as well. Turns out he told me wrong as the next two paragraphs will demonstrate.
The guy on the phone gave me the 12 series IP address that he showed being used by my VOIP device on the premises up in NC. I pulled up http://12.###.###.### (no need for me to give the actual IP address here) and got the login prompt to the VOIP unit. I entered my user name and password and got into the unit. I was also able to ping it from my DOS prompt.
The setup in the unit did indeed show at 12 series (public) IP address. So, there was no NAT from 12 to 10.
I strongly suspect that when I submitted to them that I was unhappy with having a private IP address that they re-optioned my account (the first time I called) to give me a public IP address and when the lease was up on the private IP address, my VOIP device was reassigned the public IP address (rather than give it the same private IP address again) by the cablemodem provider. I only discovered that I had a 12 series address the second time I called (only because they told me what it was).
I had my Voicepulse account (my NC phone) optioned to forward to my Vonage account (my SC phone) *if* the NC VOIP device was not communicating with Voicepulse. It had been doing this since I left the unit running at the NC residence. Dial my NC number and you would reach my SC phone. That option is still on my account. But now if you dial my NC number, you get four rings and then my Voicepulse voicemail (not my Vonage voicemail). So, I suspect that phone in that house is now working just fine. Apparently it and the Voicepulse VOIP server did not like that private IP address for some reason (or maybe it was something else that they corrected when I complained to Mediacom about my VOIP device not working on their cablemodem service).
I have learned two things from this. One, don't believe an installer on the subject of public versus private IP addresses. Two, don't be afraid to let the cablemodem company know that you are unhappy with having a private IP address so they will hopefully give you a public one instead. If your position requires any experimentation (like me teaching computer networking at the University), don't be afraid to mention that because of your work that you need a public IP address to access your network from other locations. I did mention that the first time I spoke with them. I even told them that I had an experimental Webserver that I used to learn about configuring and using Webservers on the Internet. The first guy I spoke to had no problem with that as he said he ran one on his Mediacom cablemodem as an experiment as well. But, I do think they'd get upset if you were running one as a business with a bunch of traffic. I only do it as a learning thing. No ISP *should* have a problem with that.
At any rate, I'm probably driving back up there tomorrow night. I'll know for sure whether or not it is working by then.
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