Connecting Cable Modem Through 3560 Switch

[mirsalaradili]

I have a 3560 series switch and two comcast cable modems. I connected the modems to them switch via cross over cables and set an OSPF routing on their subnets. I connected my wireless router to another port of the switch and set its gateway IP on the switch port. I can ping the modem with the switch and I can ping the wireless too. But I cannot access to the Internet via the wireless router.

Can anybody help me? Tell me what is the process to accomplish this task. I need load balancing on two cable modems and get a single network connection via the wireless router.

[mirsalaradili]

Oh thanks a lot man. So i will wait for your reply

again i appreciate it

[mirsalaradili]

Also, do you think it is possible to use the comcast modem to do the NAT? It

has a 1-NAT-1 feature.

Thanks again in advance

[yzeledon]

Hi,

After testing in the lab, I see no workaround. Maybe we should try with a different device. I have consulted other engineers and we came to the same conclusion, use a different device, do you have a router we can configure?

The modem will only do NAT for the addresses configured in the LAN segment.

Cheers,

Yanil

[mirsalaradili]

I am very grateful for your help so far.

Well I can buy one. But how much are we talking here? And also are you sure that a router that does NAT will be an answer to this task and the load balancing will be done fine?

Thanks,

[mirsalaradili]

Any specific model comes to mind? And also can we use the router and the switch together and get the results we want?

[paolo bevilacqua]

You can use, eg a 2901 that has three ethernet routed ports.

[yzeledon]

Hi,

To better recommend a model, here are some basic questions I may need to be answered:

How many users?

Besides NAT, what other features do you need? (Security, Firewall, encryption)

Traffic load? (estimated)

Any VoIP?

Any other input you can give me regarding the network.

Cheers,

Yanil

[mirsalaradili]

Well there are usually 20 to 25 users directly and almost same amount remotely.

There should be a DMZ and firewall which I think we can use the Comcast itself.

About traffic load we have some high traffic days but the load balancing between these two i think will cover it.

There are several virtual servers which each has its own public IPs that needs to be NATed and some physical servers that must have NATing process on them as well.

The thing that makes me wonder is that how is it that I can have access to the Internet through the switch itself but can't have access through another port of the switch. Are you sure there are no ways to accomplish this with current equipments? Is NAT the only way to do this? No other way around?

[mirsalaradili]

Anything comes to mind?

[yzeledon]

Hi,

First of all, let me apologize for the late response as I was out of the office. Now, to answer your question, the only reazon why the switch is able to access the internet is because it has an IP address on the range that is covered by both modems, different to the other devices that have an address on a different range.

Now, regarding the router, we can use a 2811 router, which is powerfull enough to cover the needs of the network and provide the requested features. We are going to need to add an extra card to connect to the LAN as both integrated 10/100 Fast Ethernet ports are going to be connected each to a different modem.

NAT is a feature that we are going to need for this design.

Let me know if I can be of further help.

Cheers,

Yanil

[smitty6504]

If you are going to buy a device why not look at the ASA5505 series. It provides 8 ethernet connections and does NAT. You would need to look at the different bundels to make sure it will provide a backup ethernet connecton for your secondary cable connection.

[mirsalaradili]

So what is the best way to choose which model i need? It is important that it does the load balancing without any issues. I have Cisco 1941, Cisco 2811 and ASA 5505. Which one should i choose according to my needs?

[yzeledon]

Hi,

As far as my understanding the ASA5505 will not load balance and NAT on different subnets at the same time, it will do it with 2 different IP's on the same segment, although not as what the customer is looking for.

Cheers,

Yanil

[mirsalaradili]

How about 1941 or 2811? Does it do load balancing? Also I am going to need different VLANs so i need to be able to route in different subnets.

[yzeledon]

Hi,

Both routers will do the job, I have a lot of experience with the 2811 so I can recommend you that one as it is very stable. On the other hand the 1941 is a new router that comes with support to new hardware, although for your needs we should go with the 2811!

Let me know if you need anything else.

Cheers,

Yanil