Configure 1721 on network with cable modem?

[BHEbrecht]

I seem to be having trouble getting internet when I use the Cisco 1721 Router. What I am trying to do is connect my cable modem to the router's WIC ENET card and then connecting the router's fastethernet port to a switch. I have the E0 (cable modem) set to dhcp and the Fastethernet is set to 192.168.1.1 but am not getting a connection on the computers. The router gets an ip from the cable modem and I am able to ping computers on the network and the internet from the router. I am using all straight cables. I've also tried just connecting the router staright to a computer but that didn't work either. I have a server that is assigning ip's (dhcp, domain setup) So any ideas? Here's my show run:

Router#show run

Building configuration...

Current configuration : 556 bytes

!

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Router

!

enable secret <removed>

enable password <removed>

!

ip subnet-zero

no ip routing

!

!

!

!

!

!

!

interface Ethernet0

ip address dhcp

no ip route-cache

half-duplex

!

interface FastEthernet0

ip address 192.168.1.1 255.255.255.0

no ip route-cache

speed auto

!

ip classless

no ip http server

!

!

line con 0

line aux 0

line vty 0 4

password <removed>

login

!

no scheduler allocate

!

end

Thanks in advance!

[stevensavage]

Hi

Unless I am missing something obvious - you don't have a default route setup.

ip route 0.0.0.0 0.0.0.0 Ethernet0

The Lan traffic has no way of getting out. That would explain why you can ping inside and outside from the router but not from either side.

cheers

Steve

[mhussein]

First, you need to configure nat to translate private addresses 192.168.1.x to the public ip address of interface Ethernet0:

---------------------------

interface Ethernet0

ip nat outside

!

interface FastEthernet0

ip nat inside

!

ip nat inside source list 1 interface Ethernet0 overload

access-list 1 permit 192.168.1.0 0.0.0.255

------------------------------------

And verify that your dhcp server is assigning the correct default gateway (192.168.1.1) and the correct dns servers to the clients.

I am assuming that "show ip route" shows gateway of last resort already set (obtained by dhcp from ISP)

HTH,

Mustafa

[Richard Burts]

The previous posts about default route and about NAT are good points. I notice another thing. Your router is configured with no ip routing. Is there some reason for this?

I would suggest that you configure the router with ip routing. Note that if you enter the configuration command ip routing, it will not show up when you do show run. This is because ip routing is the default and default values do not usually show up in show run.

HTH

Rick

[BHEbrecht]

Ok I did the changes to my config setup but I am still not getting any internet. I tried connecting a computer to the router with a crossover cable and I then assigned that computer an ip address through the net props and i also gave it a dns ip from the cable isp. With the access list I tried both 192.168.1.0 and 192.168.1.1, i wasn't sure which one to use. My gateway in my network is 192.168.1.1. But i didn't get any internet. Any more suggestions?

Thanks! And here is my current show run with the suggestions added:

Current configuration : 670 bytes

!

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Router

!

enable secret 5

enable password

!

ip subnet-zero

!

!

!

!

!

!

!

interface Ethernet0

ip address dhcp

ip nat outside

half-duplex

!

interface FastEthernet0

ip address 192.168.1.1 255.255.255.0

ip nat inside

speed auto

!

ip nat inside source list 1 interface Ethernet0 overload

ip classless

ip route 0.0.0.0 0.0.0.0 Ethernet0

no ip http server

!

access-list 1 permit 192.168.1.0 0.0.0.255

!

line con 0

line aux 0

line vty 0 4

password

login

!

no scheduler allocate

!

end

[mhussein]

Can you remove this line:

ip route 0.0.0.0 0.0.0.0 Ethernet0

Then verify that a default route is obtained via dhcp, using "show ip route" - please post the output here (remember to mask /or remove sensitive public ip addresses).

Try pinging Ethernet0's ip address from your pc.

Regards,

Mustafa

[BHEbrecht]

Ok I removed the ip route 0.0.0.0 0.0.0.0 e0, here is the show ip route. Not quite sure what to do here?

Router#show 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 192.168.1.1 to network 0.0.0.0

68.0.0.0/24 is subnetted, 1 subnets

C is directly connected, Ethernet0

C 192.168.1.0/24 is directly connected, FastEthernet0

S* 0.0.0.0/0 [254/0] via 192.168.1.1

[254/0] via

Thanks for all the help so far!

[mhussein]

Strange, why is default gateway set to 192.168.1.1? Is it assigned by the local "dhcp server" rather than the "ISP dhcp"? On the router, the "Gateway of last resort" should be 6x.x.x.x to network y.y.y.y

Can you:

1. Disconnect your dhcp server,

2. "reload" the router - save config first (copy run start)

(you can issue "clear ip route *", "clear arp-cache", "clear ip nat" if you don't want to reload the router)

3. then connect a pc directly (configure static ip address say 192.168.1.15, default gateway 192.168.1.1, and dns servers)

Please post the output of "show ip route" again.

[BHEbrecht]

AWESOME! Ok it seems to be working now and the ip route last resort is set to 6x.x.x.x But this was before i did the restart. After i did the restart all of my configurations were lost and the ethernet's were shutdown for some reason. And i did save it all before i restarted it. At the router prompt and i typed: copy run start and it built it. But it didn't seem to save. very strange.

Here is my current config, it's the same as show run:

Router#show config

Using 533 out of 29688 bytes

!

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname Router

!

!

ip subnet-zero

!

!

!

!

!

!

!

interface Ethernet0

ip address dhcp

ip nat outside

half-duplex

!

interface FastEthernet0

ip address 192.168.1.1 255.255.255.0

ip nat inside

speed auto

!

ip nat inside source list 1 interface Ethernet0 overload

ip classless

no ip http server

!

access-list 1 permit 192.168.1.0 0.0.0.255

!

line con 0

line aux 0

line vty 0 4

!

no scheduler allocate

!

end

Oh and now there is no password to enter the router, its like it all dissappeared as if the router was set back to default settings.

And here is the show ip route now:

Router#show 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 to network 0.0.0.0

68.0.0.0/24 is subnetted, 1 subnets

C is directly connected, Ethernet0

C 192.168.1.0/24 is directly connected, FastEthernet0

S* 0.0.0.0/0 [254/0] via

I have the route plugged in a switch and everyone is getting internet with computer's set to dhcp so they get everything from the server. So do all the configurations look good?

Thanks for everything, really do appreciate it!!

[mhussein · Accepted solution]

Good! Now your network is up and running, you may consider securing the router and the network. The 1721 router supports IOS Firewall (a.k.a CBAC). To get started, see this config example, which is somewhat similar to your configs:

http://www.cisco.com/en/US/products/sw/secursw/ps1018/products_configuration_example09186a008009445f.shtml

Regards,

Mustafa