atcomsystems.ca/forum Forums VOIP Phones & IP PBX VoIP & Cloud Phones, Hosted PBX, General IP Phones Help! Can't network system anymore!

I would be delighted to share this with you. It makes no sense to me either. I know very little about this stuff but even I don't buy it.

All that I know is that I conferenced the manufacturer's director of technical support with the best local engineer at Cox Cable that I know of. I monitored the call, heard them talk back and forth and in the end, the Cox guy said he would come up with a solution.

I am equally-curious because we have lots of situations with customers having offices across the street that are paying for P-P T1's. Now that we know of this limitation with Cox Cable, we know to be more careful about suggesting VoIP networking.

From across street to miles away, put up a radio bridge and have no monthly fees.

This is actually not that unreasonable to understand. I had this issue 2 years ago while trying to setup a vpn using Watchguard products. Fortunately for me I was able to have the ISP, change one of the locations to another subnet.

edit:

Just to clarify this not particular to cox or any other ISP for that matter. Its based in the fundementals of "ip addressing" brodcasting (arp request) vs. routing. If anybody wants me to clarify let me know.

~nails

To test this premise that everthing needs to be on the same subnet (which makes no sense to me), hook a router with 2 ethernet interfaces up. Assign the address on one side as the address your service provider gave you assign the other side with a private RFC1918 address. Let me give you a basic config. This assumes that you have multiple static IPs and you assigned 172.16.1.2 to you Vodavi card. I know they say this want work behind NAT but this is a one-to-one it SHOULD work.

interface fa0/0
ip address 8.77.55.1 255.255.255.248
ip nat outside

interface fa0/1
ip address 172.16.1.1 255.255.255.0
ip nat inside

ip nat pool WORD 172.16.1.2 172.16.1.2 netmask 255.255.255.0

ip nat inside source static 8.77.55.2 172.16.1.2

access-list 10 permit 172.16.0.0 0.0.255.255

ip nat inside source list 10 interface f0/0 overload

Can't you re-work one side to a different subnet yourselves? Or because they are public is this not possible?
Also if you are using VLANS then all users must be on the same vlan to see each other unless you have a router to to route to different VLANS, this is confusing with this ISP in there so I'm having a hard time picturing the set up in my mind.
I would suggest putting switches on each side with a router as well somewhere in there and a point to point connection. Then get your own IP block and do all the subnetting you want your way.

Well, it's funny you asked. Our solution had become a requirement for commercial routers at each end, plus more of them for the owner's IP phones at their homes. That was cost-prohibitive and unacceptable for the customer, not to mention the inability to use WIFI devices in public places. I may not have mentioned, but at this time, Vodavi doesn't support NAT, so a VPN would be difficult when working with endpoints outside of the network.

The cable company acknowledged today that there's no way they can accommodate us any other way due to the general plant architecture, so they agreed to let the customer out of their contract. The customer is having DSL installed through Verizon at one site next week. That way, each site will be on a different gateway and this problem will (hopefully) resolved.

It's important to note that if you encounter a customer wanting to network sites together via cable that you make sure that the addresses are on different nodes in the provider's network. If not, the customer needs to be told that routers will be mandatory. We assumed that we could just transfer their "router-less" setup to the new address and we were wrong. After about two months, I am relieved to say that there is some light at the end of the tunnel. The customer is also happy that we are reaching a conclusion.

I am actually very impressed with the people at Cox who have been working with us on this matter because unlike the LEC (un-named), at least they have actually tried to fix the problem instead of just blaming others like "you know who".

I will post back once everything is done to let you all know the final outcome.

Here’s the deal why this will not work.

When a networking device receives a packet for another device, it does basically one of two things. 1) Send out an ARP request or 2) Forward to the gateway. In this case the Vodavi switch received a packet request for a device within the same subnet (subnet does matter), by default it will do nothing other than send out an ARP request (a call out for the mac address associated with the IP address). However the network attached to the Vodavi switch is the internet, and for all intensive purposes the internet disregards these packets since they are layer 2 broadcasts.

Since this is only temp a solution I would have configured one side to DHCP. Around here Cox splits the DHCP clients and Static clients into 2 very distinct subnets. Depending on the Vodavi capabilities there may be a setting that allows for the DHCP side to initiate contact with the static side and update any address changes (many VPN devices support this feature now). If not, you could manually enter the destination of the static side to the address given by the DHCP side. From experience, I have clients that use DHCP and rarely have to change settings, many times a DHCP address will not change for months.

Vodavi doesn't support NAT? Wouldn't your routers do that if you had any?

DW:

From what I have been told by Vodavi, the answer is no. We have never had success getting their system networking to function behind routers. We have always installed a small switch ahead of the customer's router and relied upon static IP's. It worked very well for years until this site on the same carrier node came into play.

NAT is in the works with Vodavi, but as of today, it has not been accomplished. Don't ask me why, I have very little understanding of IP. All I know is what I am learning along the way, but even the cable company (COX) has admitted that without a significant investment in routers for the multiple sites, it can't be done.

The whole problem here is that the customer had a perfectly working IP setup for over a year, so they don't feel that they should have to spend $2K for routers and for various IT guys to get involved when all they did is move to a new site across the street. I can't say that I disagree.

Does not matter if you invest in router or not. If you have router A with the same address as Vodavi A and router B with the same address as vodavi B, you still have the same issue as i explained it above. Routers route... that means it sends packets between subnets. You have two IPs in the same subnet.