VLAN to WAN Assitance

[jasonskaggs]

I need some assistance please, I need to create a VLAN for our public internet. I have a cable modem (plug and play, nothing i can configure) and would like to be able route this VLAN out this modem if possible. I also need to have DHCP on this VLAN as I need more than the 8 IP's the provider has allotted us on the modem. Here is how I set it up so far:

ip dhcp pool Public
   network 10.0.48.0 255.255.252.0
   default-router 10.0.48.1
   domain-name mydomain.com
   dns-server "Cable Provider DNS entries"

   lease 0 12

interface Vlan31
ip address 10.0.48.1 255.255.252.0

The DHCP is working however I am unsure on how to connect the Modem to the VLAN and redirct the traffic out if its even possible.

[jasonskaggs]

Little more detail on the hardware, its 4510r-E with sup V-10G

[Amit Singh]

Could you please attach a diagram to show what you want to achieve?

As far as modem is configured to go to the internet an dits providin you the local IP's you can reach the internet. Are you looking to host some server over the internet so that users over the internet can reach out to those?

Cheers,

[jasonskaggs]

The diagram is basically like this:

Computers --> Vlan 31 (getting DHCP from Vlan 31 on the switch) --> Internet browsing for the computer in this VLAN only.

Don't need to host any servers, just need to it so these computers get a DHCP address and can surf the internet. I do have customer IP's for the modem.

[Jon Marshall]

Jason

You need a couple of things.

1) If the provider have you some public IPs then they should have provided a default-gateway as well. If that DG is from the public IPs then you would  need to assign one IP to the 4500 eg.

int gi0/1 <-- connects to cable modem

ip address x.x.x.x

ip route 0.0.0.0 0.0.0.0

then the 4500 would forward all unknown traffic to the ISP default-gateway.

2) You will need to NAT your 10.x.x.x addresses. Unfortunately the 4500 switch does not support NAT so it will have to be on the cable modem which should be able to do it. If it can't then you will need a device that can NAT between the 4500 and the cable modem. This could be a router (pretty much all routers support NAT) or an ASA firewall which also supports NAT.

On a more general note you should have some sort of firewall between your 4500 and the internet anyway.

Jon

[jasonskaggs]

Thanks Jon, that is everything I needed.