Link to home
Start Free TrialLog in
Avatar of cjlinder
cjlinder

asked on

How do I configure a LAN port on a Cisco 1841

I have a Cisco 1841 that has two FastEthernet ports.  I want to configure one port as a LAN port to talk to my PC and the other as a WAN port talking to my AirLink Raven X modem.  I have FE 0/0 configured with IP address 192.168.13.100 that is directly connected to my AirLink modem with a gateway address of 19.168.13.31 and a fixed pulblic IP on the WAN side.  Using the CLI I have successfully configured this FE port so I can ping out to any IP on the internet (using the CLI).  I have FE0/1 port configured with IP address 192.168.15.100 and using the CLI have successfully configured DHCP on this port so the PC connects to it.  From the PC, I can successfully ping 192.168.15.100 and 192.168.13.100 but cannot ping 192.168.13.31 which is my modem gateway on the LAN side.  I need to be able to ping out (connect) to the internet from my PC, but am unable to thus far.  Attached are a couple screen shots showing my IP route and running-config.  Please help.
Noname.jpg
Noname1.jpg
Avatar of GJHopkins
GJHopkins
Flag of Afghanistan image

Does the modem at 192.168.13.31 have routes back to 192.168.15.0 ? If not you will have to add them or use NAT on this router.

An observation :

the static routes int he router to 192.168.13.0 and 192.168.15.0 will never be used as these are connected interfaces on the route, not causing a problem but could be removed.
yeah, your modem needs to know how to route the return traffic. the ping from you PC is getting to the modem, but the modem does not know where to send the return traffic.

if you are unable to configure routes on the modem, then i would suggest using NAT.  you can make fa0/0 the outside interface and fa0/1 the inside interface.  NAT all traffic from the inside, the an IP address in 192.168.13.xx range.  Then the modem will know where to send the return traffic
the an IP address in 192.168.13.xx range  = then use an IP address in the 192.168.13.xx range
Avatar of cjlinder
cjlinder

ASKER

Sounds like there is consensus that I don't have a properly defined return route from the modem at 192.168.13.31 to my PC at 192.168.15.0.  I'm unclear how to define this so any examples would be really helpful.  Thanks much.
use the Sierra Ace View gui to configure the modem.

all you need to do is add a route that says for 192.168.15.0 traffic to be sent to 192.168.13.100.

ok, so i happen to have and Raven X modem and did not see anywhere in the GUI on how to configure additional routes.  i would suggest using NAT on your Cisco router.  It is pretty easy to setup.

do this
config t

access-list 55 permit 192.168.15.0 0.0.0.255
ip nat inside source list 55 interface overload

int fa0/0
ip nat outside
int fa0/0
ip nat inside

end
wr

this will give everything with an IP address of 192.168.15.0 that goes to the modem the ip address of 192.168.13.100

that way the modem will now know where to send the return traffic.
oops, the config should look like this:

config t

access-list 55 permit 192.168.15.0 0.0.0.255
ip nat inside source list 55 interface overload

int fa0/0
ip nat outside
int fa0/1
ip nat inside

end
wr
I'm trying your commands but getting an error as shown below in the attachment.  Let me know your thoughts.
Noname2.jpg
I tried using a "?" mark after the command where I received an error right before 'overload' and this is what it dislayed.  BTW I really appreciate your help.  You're extremely knowledable.   Thanks again.

Noname3.jpg
ASKER CERTIFIED SOLUTION
Avatar of ngravatt
ngravatt
Flag of United States of America image

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
That did it!  You are so Awesome!!!  "We're not worthy" from Wayne's World comes to mind.

Thanks again so much.
This expert is Awesome!!!
ha. thanks man. glad i could help