Connecting comcast internet to home lab

[Gregaku]

Hi

I have comcast internet that is coming from a Arris Mode SB6180, the comcast IP address is 73.56.x.x. I need to be able to set up the WAN to my Cisco 2811 router, the mode is not set as DHCP, I connect  the cable coming the ARRIS modem to f0/0 port (cisco 2811) and when I ran the command ip address dhcp, it's not getting any Ip from the modem, I'm not sure about what comcast subnet could be.

I have f0/1 port already set up as DHCP server connected to a switch with 4 laptops, DHCP is active, all my client obtained their IP address from the dhcp 10.10.10.0 /24.

Any idea on how I can set up the WAN on the cisco switch so my clients can have internet?

[balaji.bandi]

the comcast IP address is 73.56.x.x

how do you know this ip coming from ISP, have you connected the Laptop and able to get this IP address ?

what IP you get when you connect to comcast Modem your Laptop ?

May be i am thinking Comcast expecting VLAN i am in guess. ?

Options 1 :

interface FastEthernet0/0
ip address 10.x.x.x 255.255.255.0 ---> this IP if you have Lap IP providing the DSL Modem 10.X range you can use any IP that is no the gateway IP)
ip nat outside
ip virtual-reassembly
no ip route-cache
duplex auto
speed auto
no mop enabled
!
interface FastEthernet0/1
ip address x.x.x.x 255.255.255.0 (you Lan side IP you confirmed all working)
ip nat inside
ip virtual-reassembly
no ip route-cache
duplex auto
speed auto
!
!
ip classless
ip forward-protocol nd
!
!
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
access-list 100 permit ip x.x.x.x 0.0.0.255 any (your Lan IP address ranges)
ip nat inside source list 100 interface fa0/0 overload
!

Option2 :

interface FastEthernet0/0
ip address dhcp
ip nat outside
ip virtual-reassembly
no ip route-cache
duplex auto
speed auto
no mop enabled
shutdown

give 1min and then issue no shutdown

check show ip interface brief to see the Interface got IP address.

run DHCP debug :

debug dhcp detail 

[Gregaku]

Thank you for your reply, I will try them later, but I got to say this, I was completely wrong about the comcast IP address, the 73.56.46.XX was coming from "whatismyipaddress.com and ip chicken, the IP that came up after I cleared the previous config that I had in my network adapter is 10.10.10.10 with a GW 10.10.10.1, I will try again later and I will keep you posted, again thx for your help.

[balaji.bandi]

Sure when the device NAT with Public IP so you get that IP address when you see what is my ip address site.

let us know how that goes my suggestion or any issue post here more information 

[Gregaku]

Hi balaji.bandi

Preview

Just wanted to give you an update, I'm still not getting internet, I've issued the commands that you suggested but the router and my workstations are still not connected to the internet, here's my running config 

R2(config)#do sh run
Building configuration...

Current configuration : 1558 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R2
!
boot-start-marker
boot-end-marker
!
logging message-counter syslog
!
no aaa new-model
clock timezone EST -5
no network-clock-participate wic 0
no network-clock-participate aim 0
!
dot11 syslog
ip source-route
!
!
ip cef
ip dhcp excluded-address 172.16.50.1 172.16.50.5
!
ip dhcp pool LAB
network 172.16.50.0 255.255.255.0
dns-server 8.8.8.8
domain-name aku-sys.com
default-router 172.16.50.1
!
!
no ipv6 cef
!
multilink bundle-name authenticated
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
voice-card 0
no dspfarm
!
!
!
!
!
archive
log config
hidekeys
!
!
!
!
!
controller T1 0/0/0
framing esf
linecode b8zs
!
!
!
!
!
interface FastEthernet0/0
ip address 10.10.10.30 255.255.255.0
ip nat outside
ip virtual-reassembly
no ip route-cache cef
no ip route-cache
duplex auto
speed auto
no mop enabled
!
interface FastEthernet0/1
ip address 172.16.50.1 255.255.255.0
ip nat inside
ip virtual-reassembly
no ip route-cache cef
no ip route-cache
duplex auto
speed auto
!
interface FastEthernet0/2/0
no ip address
shutdown
duplex auto
speed auto
!
ip forward-protocol nd
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
no ip http server
no ip http secure-server
!
!
ip nat inside source list 1 interface FastEthernet0/0 overload
!
access-list 1 permit 172.16.50.0 0.0.0.255
!
!
!
!
!
!
!
control-plane
!
!
!
!
!
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
scheduler allocate 20000 1000
end

R2(config)#

Preview

[balaji.bandi]

post below output :

show ip interface brief

show ip route

show ip arp

ping 10.10.10.1 (thinking this is comcast Router IP address Lan side)

If the work station connection, what IP work station getting ?

is the work station directly connected to Router or any other switch ?

if the work station able to ping 172.16.50.1  and 10.10.10.30  and 10.10.10.1 and 8.8.8.8 ?

post all the output.

[Gregaku · Accepted solution]

Hello balaji.bandi

I was able to figure out what the issue was, everything was setup correctly, the only thing that I had to do was to reboot the comcast modem after issuing the command ip address dhcp on the interface that the cable coming from the modem was connected, thank you for your assistance.

[balaji.bandi]

Glad our suggestion made you to fix the issue.