Cisco 1811 behind Comcast Cable DHCP

[gpan667788]

Hello all,

I just got Comcast internet with dynamic ip. I am installing cisco 1811 behind the comcast modem. But I cannot send the traffic out. I tried with and w/o BVI option in 1811 but still does not work. Does anyone have any suggestion?

Here are some basical config:

int fas 0

ip add dhcp

ip nat outside

int vlan 1

ip add 192.168.0.1 255.255.255.0

ip nat inside

ip nat inside source route-map NoNat interface fas 0 overload

ip access-list extended NATList

deny ip 192.168.0.0 0.0.0.255 10.0.0.0 0.255.255.255

deny ip 192.168.0.0 0.0.0.255 172.16.0.0 0.15.255.255

deny ip 192.168.0.0 0.0.0.255 192.168.0.0 0.0.255.255

permit ip 192.168.0.0 0.0.0.255 any

!

!

route-map nonat permit 10

match ip address NATList

ip route 0.0.0.0 0.0.0.0 FastEthernet0 name DefaultRouteToComcast

I called Comcast; they said the modem only allows one config and they don't know how to config anything behind the modem other than PCs.

Any help will be greatly apprecated!

thanks,

Gene

[mikegrous]

first off. Is the FAS interface getting a DHCP Address from comcast?

[Collin Clark]

When you plug your PC into the modem, does it get a public or private IP address?

[gpan667788]

Public Address.

If I use router's fe 0 dhcp, I am getting completed different class of public ip than PC gets.

thanks,

[Collin Clark]

Once you plug in the router and get an IP, can you ping the default gateway?

[gpan667788]

Don't know the default gateway if I use router. The ip I am getting is like 24.x.x.x different than the IP I am getting from PC 74.x.x.x. If I hard code the 74.x.x.x and default gateway into router fe interface and setup the default route, then I can ping.

thanks,

[Collin Clark]

OK, let's move forward and address that later. Can the router ping an internet address like 4.2.2.2? If yes, can the router ping it when you source from the LAN side?

[gpan667788]

No, cannot even ping anything outside before the extended ping.