New ISP connection not working properly

We have a new ISP.  It is a /29 block of static IPs through Time Warner Cable Business Class.  Our old service was a T1 with a /28 block of static addresses.  (We have drastically reduced the number of devices needing to connect so when we ordered the new service we cut it to a /29 block.)

The old service worked exactly as expected.  I could connect any device to the service, configure one of the unused IPs using subnet mask and it worked fine.

Thus far we have been unable to get the new service to work properly.  When we connect a laptop to the modem and configure one of the new IPs with a subnet mask of, the laptop works correctly, as expected.

However, when we connect any other device they do not work.  We've tried a DVR surveillance system, a firewall and a router.  When connected to the new service we can't ping them.  We know they are responding to the ICMP requests when received because they respond when connected to the old service.  If we take a properly configured laptop connected to one of the Ethernet ports on the new modem we can ping the other devices that are also connected to the modem.  So, again, the devices are responding.  But we can't ping them from the Internet side.

TWCBC insists the connection is working and their only guarantee is that the connection is good to the modem.  They are not responsible for any devices connected to the modem.  They claim they don't block any ports on the Business Class Service.

We are going to make a decision tomorrow about whether to just terminate the new service and keep our old service.

Suggestions please.
Kerry WilsonNetwork AdministratorAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

What type of modem?

Who is responsible for the configuration of the modem?
Kerry WilsonNetwork AdministratorAuthor Commented:
It is an Arris.  I think the Model # is SBG6508.  But I'm not 100% sure as I'm at home right now.

TWC is responsible for the configuration and because it is business class they will not give me access to it via the web-based UI.

It is interesting that you targeted the modem.  After my original posting it occurred to me one of the TWC technicians made a comment today that escaped me at the time as to its possible significance.  He mentioned this is the same modem they use for their residential service.  Their network people had decided to reduce the number of different modems held in their inventory and this model was one they believed to be a good pick for both residental and business class.

Now I am wondering perhaps this model is not suitable or capable of configuring for multiple static IPs (like a /29 block).  That does not explain why it works properly for laptops though and it does not work properly for other devices.  Or, if it is capable, perhaps they don't have it configured properly since they normally use it in residential service and they don't know how to configure it for multiple static addresses.

I have a feeling the modem will work fine for 99% of small businesses because most businesses do not need multiple static IPs.  Most businesses would just use DHCP connection to a router.  Please excuse the rambling.  :-)
Do you mean SBG6580?  If so, I don't think that modem can deal with multiple WAN-side IP addresses, no matter HOW you configure it.

You might be able to get into its configuration using user admin and password motorola.
Your Guide to Achieving IT Business Success

The IT Service Excellence Tool Kit has best practices to keep your clients happy and business booming. Inside, you’ll find everything you need to increase client satisfaction and retention, become more competitive, and increase your overall success.

If it is a Arris SBG6580, then is really a Motorola SURFBoard Cable modem, 4 port ROUTER, and Wifi Access point.  Which is targeted for home use.

When you configured an IP address on the laptop, was it a 192.168.1.x address or was it one of the public IP addresses that Time Warner gave you?

From the one manual I found, this seems to be like most other home routers.  That is, it has a SINGLE outside/public IP address and everything "inside" uses a address and the device does many to one NAT'ing.

That is based on what I read here:

If that is true, then there is no way to use a /29.
Well, just a few minutes after mu last post, I did some more searches.  It seems that the SBG6580 can be setup in bridge mode, which means it acts just like a switch and will pass through any data.  

This means you should be configuring your devices with the public IP addresses that wee assigned to you by Time Warner.  Which I am assuming you were doing.

However, since you can get to admin page you have no way to verify they setup the modem correctly.

If possible I would get two computers and connected them to the modem, get then configured with two of your IP addresses with the proper subnet mask.  

If they can ping each other, but can NOT get to the Internet, call Time Warner.  They should be able to get into the modem and see that there are two devices connected.  If need be, you might have have give them remote access to the one than can get to the Internet to prove that it can ping the other one.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Kerry WilsonNetwork AdministratorAuthor Commented:
But, if we hook up two laptops to the LAN side, it works correctly...both laptops work and can be pinged from the Internet.  So, it seems it *is* working correctly with multiple, static least with laptops.

But any other devices (router, firewall, DVR) connected to the LAN side will not connect to the Internet and can't be pinged from the Internet.  However, the laptops on the LAN side can ping the other devices.

One other "weird" thing I just noticed last night looking at the hardware configuration on my TWC modem at my residence (I think it's the exact same model), is that all four of the LAN ports are shown to have the exact same MAC address.  Is that okay??  It seems to me that could cause routing issues (the local surveillance system tech and I both had thought originallly it was a routing issue based on our testing).
Ah.  Does ping'ing the firewall/DVR/router work with your current/old ISP?

Did you update the default router/gw on the DVR and router when you tried them.

Did you update/change any policies on the firewall?  Especially since firewalls typically don't allow themselves to be ping'ed.
Kerry WilsonNetwork AdministratorAuthor Commented:
Yes, the other devices respond when ping'ed from the Internet on our old service.

Yes, we updated all of the settings on the devices to work with the new (TWC) service.

No changes to any firewall policies.  Our firewall does respond to a ping from the Internet on the old service.
When you connect the nonworking devices, what are you telling them the gateway address is?  Assuming that the Arris is correctly configured as a bridge, wouldn't anything that is directly connected to the Arris need to know that the gateway address is the LAN address of the router to which the Arris is connected on the Arris' WAN side?
Kerry WilsonNetwork AdministratorAuthor Commented:
Our address block is:  nnn.nnn.nnn.0/29

We were told the gateway is .1 and the usable addresses are ,2 through .6

We are using subnet mask for the devices and a .1 address for the gateway.  Laptops work but other devices do not.  We are using the same settings.  As a matter of fact, if we have a laptop at .5 and the DVR at .6 we can ping the laptop but not the DVR.  Then if we "swap" the addresses where the only thing we change is we put the laptop at .6 and the DVR at .5 we can still ping the laptop but not the DVR.

This is not the case with our old connection.  We can ping both of them.
For the DVR, does it have two LAN connections or are you moving it from one ISP connection to the other?
If it has two, since a device can only have one default route, you may need to disable the LAN interface you are currently using so that it will use the default route on the second interface.
Kerry WilsonNetwork AdministratorAuthor Commented:
Just one connection...moving it from one service to the other.

It is connected directly to the service for firewall between it and the service.
Kerry WilsonNetwork AdministratorAuthor Commented:
As it turned out there were multiple problems at the network end.  I don't know if we could have gotten the SBG6580 to work or not.  We didn't find the network problems until after the tech had installed a different modem.  He agreed there were issues with the network setup and made two or three phone calls to his support desk.

But, we finally got the new connection working and all is well.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Network Management

From novice to tech pro — start learning today.