Cisco 1841 on Zyxel C1100Z

[Trevor Janssen]

Hello,

I am having issues with my 1841 that I recently bought. I am trying to configure my router to get on to my ISP, CenturyLink. I have tried configuring FE0/0 as the WAN port and FE0/1 as the LAN port, when I try to get on the Internet, it simply doesn't work and gives me the error "There is no Internet connection", note that this is in Google Chrome. I then tried to ping the backend of my ISP only to figure out that doesn't work either. I tried to ping my backend from the router itself and it worked. So I assumed that there wasn't a route to get to the backend. I then configured a default route to get there and ultimately it didn't work. I need help getting it configured.

[Francesco Molino]

Hi

Let me do a recap just to be sure I understood your issue.

1. You have your fe0/0 interface that's in DHCP, right?
2. From your router, you have a default route, right?
3. From your router, if you ping 8.8.8.8, you get answer, right ?
4. From your PC, you don't have internet access, right?

For the default route on the router, in case the router itself don't have internet access:

ip route 0.0.0.0 0.0.0.0 f0/0

OR

ip route 0.0.0.0 0.0.0.0 dhcp ==> If your ISP is sending a default route from DHCP

Now, let's assume your internal LAN subnet is 192.168.0.0/24

you need to do batting, below a sample config (need to be adapted if your LAN subnet is different):

ip access-list extended NAT

 deny ip 192.168.0.0 0.0.0.255 192.168.0.0 0.0.0.255

 permit ip 192.168.0.0 0.0.0.255 any

!

interf f0/0

 ip nat outside

interf f0/1

 ip nat inside

!

ip nat inside source list NAT int f0/0 overload

Hope this is clear.

PS: Please don't forget to rate and mark as correct answer if this solved your issue.

[Trevor Janssen]

I have done that, still doesn't work. Anything else I can do? Btw, my internal address is 192.168.1.0 255.255.255.0. 

[Trevor Janssen]

and the subnet for my external address is 138.210.32.0 255.255.248.0

[johnlloyd_13]

hi,

kindly post a show run output.

[Francesco Molino]

You have modified the subnet on the NAT acl?

In addition of sh run output, could you provide the sh ip route output?

Are you able to ping 8.8.8.8 through your router?

Thanks 

PS: Please don't forget to rate and mark as correct answer if this solved your issue 

[Trevor Janssen]

I am unable to ping 8.8.8.8 let alone the default gateway for my ISP. I will provide the sh IP route and sh run when I get home.

[Trevor Janssen]

SVR-RT(config)#do sh run

Building configuration...

Current configuration : 1108 bytes

!

version 12.4

service config

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname SVR-RT

!

boot-start-marker

boot-end-marker

!

enable secret 5 $1$k872$R73zLckuOCrgOBnnqFk0k.

enable password mario240

!

no aaa new-model

no ip routing

no ip cef

!

!

!

!         

!

!

!

!

!

!

!

!

!

interface FastEthernet0/0

ip address 192.168.1.1 255.255.255.0

ip nat inside

ip virtual-reassembly

no ip route-cache

speed auto

full-duplex

no mop enabled

!

interface FastEthernet0/1

no ip address

ip nat outside

ip virtual-reassembly

no ip route-cache

duplex auto

speed auto

!

ip route 0.0.0.0 0.0.0.0 FastEthernet0/1

ip route 138.210.32.0 255.255.248.0 FastEthernet0/0

!

!

ip http server

no ip http secure-server

ip nat inside source list NAT interface FastEthernet0/0 overload

!

ip access-list extended NAT

deny   ip 192.168.1.0 0.0.0.255 192.168.1.0 0.0.0.255

permit ip 192.168.1.0 0.0.0.255 any

!

snmp-server community public RO

!

!

!

!

control-plane

!

!         

!

line con 0

line aux 0

line vty 0 4

password mario24

login

!

scheduler allocate 20000 1000

end

SVR-RT(config)#do sh ip route

Default gateway is not set

Host               Gateway           Last Use    Total Uses  Interface

ICMP redirect cache is empty

[Francesco Molino]

You said that f0/0 was your wan and f0/1 was your lan.

In your config, f0/0 is your lan and no ip on f0/1.

If you have connected your wan link on f0/0 you need to invert the config of your interfaces. 

Ip nat outside as to be set in wan interface.

Why you have set a route to 138.210.32.0?

Are these addresses your public IPs?

If yes you need to configure one of this pool on your wan interface. In that case your isp gave you the IP of their router in this range. If that's the case, your default route must point to this isp router ip instead of f0/0.

If your wan has to be in dhcp then you need to set the command ip address dhcp on your wan interface configuration and default route ip 0.0.0.0 0.0.0.0 dhcp

Right now your default route is pointing to f0/1 that's your lan interface (based on your 1st post description)

How this is clear?

Thanks 

PS: Please don't forget to rate and mark as correct answer if this solved your issue 

[Trevor Janssen]

I got lazy and put F0/1 as WAN as that was connected to my modem and F0/0 as my LAN. *facepalm*

[Trevor Janssen]

I have set the IP as DHCP and I did a ping to my backend default gateway from my PC and it failed the ping

[Trevor Janssen]

I am able to ping 8.8.8.8 from my router.

[Trevor Janssen]

I also have a Cisco switch that connects to the 1841.

[Trevor Janssen]

Here is the new config:

SVR-RT(config)#do sh ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route

Gateway of last resort is 0.0.0.0 to network 0.0.0.0

138.210.0.0/21 is subnetted, 1 subnets
C 138.210.32.0 is directly connected, FastEthernet0/0
S* 0.0.0.0/0 is directly connected, FastEthernet0/0

SVR-RT(config)#do sh run
Building configuration...

Current configuration : 810 bytes
!
version 12.4
service config
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SVR-RT
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
ip cef
!
!
!
!
!
!
!
!
!
!
!
!
!
interface FastEthernet0/0
ip address dhcp
ip nat outside
ip virtual-reassembly
duplex auto
speed auto
!
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat inside
ip virtual-reassembly
shutdown
duplex auto
speed auto
!
ip route 0.0.0.0 0.0.0.0 FastEthernet0/0
!
!
ip http server
no ip http secure-server
!
ip access-list extended NAT
deny ip 192.168.1.0 0.0.0.255 192.168.1.0 0.0.0.255
permit ip 192.168.1.0 0.0.0.255 any
!
!
!
!
!
control-plane
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
scheduler allocate 20000 1000
end

[johnlloyd_13 · Accepted solution]

do:

no ip route 0.0.0.0 0.0.0.0 FastEthernet0/0

no ip access-list extended NAT

access-list 1 permit 192.168.1.0 0.0.0.255

ip route 0.0.0.0 0.0.0.0 dhcp

ip nat inside source list 1 interface f0/0 overload