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Beginner here. For the life of me, I cannot get my Cisco 1841 router to connect to the internet (home lab)

The51stAgent
Level 1
Level 1

Hello. I thought with the things I have learned at this point, that I could simply figure out how to connect my 1841 to my ISP router and from there, be able to plug a host in to the one free fast ethernet port on my router and reach the web. But this has been driving me crazy for over a week. I read other guides online for this but nothing is working, so forgive me for asking what may be a tired question. I would be very appreciative if anyone could help me. I'm going to slightly alter the Public IP I suppose just for privacy's sake, but here goes:

My ISP router's Public IP is 74.182.7.137 with subnet 255.255.252.0

My ISP router's private IP is 192.168.1.1 with subnet 255.255.255.0

Port Fe0/0 of my Cisco 1841 is set to 192.168.1.2

 

I have a straight through cable running from one of the ports of my ISP router into interface Fe0/0 on my Cisco 1841 router. Shouldn't I be able to get this router fully online and plug my laptop into Fe0/1 and reach the web?
I could post running-configs and show ip interface briefs but to be honest, it would probably be a waste of time, as I am sort of spitballing here and am sure I am entering things wrong. Could someone please advise me on the commands needed to make this work? I think I am understanding that one port/interface needs to be configured with an address of the public range and the other needs to be configured with the address of the private range, but I tried this and the most progress I saw was being able to successfully ping 192.168.1.1 and 192.168.1.2 but could not ping any websites from my Cisco router. Should the gateway of last resort be the private address of my ISP router or it's public address? Does my ISP router need to be bridged? Please help! I am so lost and if I can get some guidance on this it would really help things click for me.
Thanks!

1 Accepted Solution

Accepted Solutions

Hi @The51stAgent ,

 

I found a detail in your configuration. Try this change and try again:

 

interface FastEthernet0/1

 ip address 172.16.0.1 255.255.0.0

 ip nat inside

 

Regards

View solution in original post

6 Replies 6

Martin L
VIP
VIP

the gateway of last resort should be 192.168.1.1
can you ping 8.8.8.8 ? if so, then try ping google.com

other issues:
1. you already have ISP router with NAT, DHCP, DNS, and your ISP is already doing NAT. ISP router's private IPs are being NAT'ted to Private IP.

luis_cordova
VIP Alumni
VIP Alumni

Hi @The51stAgent ,

 

Try this.

 

Router(config)#ip dhcp excluded-address 172.16.0.1 <-- LAN gateway

Router(config)#ip dhcp pool LAN <-- Address pool for LAN PCs

Router(dhcp-config)#default-router 172.16.0.1

Router(dhcp-config)#network 172.16.0.0 255.255.0.0

Router(dhcp-config)#dns-server 8.8.8.8 <--  dns of google

Router(dhcp-config)#ex

 

Router(config)#int f0/0

Router(config-if)#ip ad 192.168.1.2 255.255.255.0 

Router(config-if)#ip nat outside

Router(config-if)#no shutdown

Router(config-if)#ex

 

Router(config)#int f0/1 <-- LAN interface

Router(config-if)#ip ad 172.16.0.1 255.255.0.0 <-- LAN gateway

Router(config-if)#ip nat inside

Router(config-if)#no shutdown

Router(config-if)#ex

 

Router(config)#ip route 0.0.0.0 0.0.0.0 192.168.1.1 <-- ISP router's private IP

 

Router(config)#access-list 1 permit 172.16.0.0 0.0.255.255 <-- List that allows the LAN network

Router(config)#ip nat inside source list 1 interface f0/0 overload <-- Associate the list with the exit interface

Router(config)#do wr

 

Regards

Thank you, guys, for the responses. It's appreciated more than you know. Luis- I entered your suggested configuration but I still cannot reach the web from my host plugged into fe0/1. I can ping 8.8.8.8 without issue, but when I ping google.com, I get "Translating "google.com"...domain server (255.255.255.255)

% Unrecognized host or address, or protocol not running"

This is my show running-config:

 

router#show running-config

Building configuration...

 

Current configuration : 1343 bytes

!

! Last configuration change at 01:00:58 UTC Fri Aug 23 2019

version 15.1

service config

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname router

!

boot-start-marker

boot-end-marker

!

!

!

no aaa new-model

!

dot11 syslog

ip source-route

!

!

ip dhcp excluded-address 172.16.0.1

!

ip dhcp pool LAN

 network 172.16.0.0 255.255.0.0

 default-router 172.16.0.1

 dns-server 8.8.8.8

!

!

!

ip cef

no ipv6 cef

!

multilink bundle-name authenticated

!

crypto pki token default removal timeout 0

!

!

!

!

license udi pid CISCO1841 sn FTX150804LK

!

redundancy

!

!

!

!

!

!

!

!

!

interface FastEthernet0/0

 ip address 192.168.1.2 255.255.255.0

 ip nat outside

 ip virtual-reassembly in

 duplex auto

 speed auto

!

interface FastEthernet0/1

 ip address 172.16.0.1 255.255.0.0

 ip nat outside

 ip virtual-reassembly in

 duplex auto

 speed auto

!

interface Serial0/0/0

 no ip address

 shutdown

!

interface Serial0/1/0

 no ip address

 shutdown

!

ip forward-protocol nd

no ip http server

no ip http secure-server

!

!

ip nat inside source list 1 interface FastEthernet0/0 overload

ip route 0.0.0.0 0.0.0.0 192.168.1.1

!

access-list 1 permit 172.16.0.0 0.0.255.255

!

!

!

!

!

!

control-plane

!

!

!

line con 0

line aux 0

line vty 0 4

 login

 transport input all

!

scheduler allocate 20000 1000

end



Hi @The51stAgent ,

 

I found a detail in your configuration. Try this change and try again:

 

interface FastEthernet0/1

 ip address 172.16.0.1 255.255.0.0

 ip nat inside

 

Regards

SUCCESS! Thank you, Luis!! And to the others that responded! You guys all rock!

Hello,

 

post the full running configuration of your 1841. What you need is double NAT, of which luis_cordova has given you the settings. You might have missed something...

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