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Newbie Cisco 2600 problem 1

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tomsoft

tomsoft

Programmer
Oct 20, 2006
3
US
I have commercial DSL service with 5 static addresses. I have been using off-the-shelf LinkSys residential routers with port-forwarding to host some web servers under each of the LinkSys routers. I recently decided to upgrade to a ‘real’ router and bought a used Cisco 2600. I’ll be damned if I can get the routing to work.

All I am trying to do for now is to get a single host on LAN side of the Cisco router to be able to ping the underside of the DSL router. I’m sure there is something simple and stupid I am doing wrong. Here are the details (some leading octets altered in the name of security):

DSL Modem LAN-side (gateway) address: 167.127.130.158

I have addresses 153-157

Here is my running-config. There is a PC sitting at 10.0.0.6 that can ping 10.0.0.1 and 167.127.130.157 but not the next hop (DSL router) at 167.127.130.158 or anything else on the internet. From the router I can ping 167.127.130.158 or anything else on the internet and I can also telnet to the router over the internet.

interface FastEthernet0/0
ip address 167.127.130.157 255.255.255.248
no ip mroute-cache
speed auto
full-duplex
!
interface FastEthernet0/1
ip address 10.0.0.1 255.255.255.0
no ip mroute-cache
duplex auto
speed auto
!
ip classless
ip route 0.0.0.0 0.0.0.0 167.127.130.158
ip route 10.0.0.0 255.255.255.0 FastEthernet0/0
no ip http server
!
!
line con 0
transport input none
line aux 0
line vty 0 4
 
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..so let me see if i got this right..

---(.157)2600(.1)---10.0.0.0/24----(your server)

...so your server is not getting pings back from 167.127.30.158 (your dsl modem).
...your dsl modem doesnt know how to get to 10.0.0.0 (it would also need a static route like *ip route 10.0.0.0 0.0.0.255 167.127.30.157* ..but you obvioulsy cant do this..
...so you will have to configure nat/pat..
....if i was you..i would also buy a adsl wic card... (i am currently using one with bellsouth dsl in my 2600) (takes the modem out of the picture)


..below is a configuration example of nat.
..there are many examples similar to this...you can easily find one more similar to your problem
...just pretend the atm port is your fast0/0


..how this helps!


CCNP,CCSP,MCSE,Sec+,Net+,A+...
 
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Thank you - this looks like it will be useful. I am still somewhat confused however. I knew that I would need NAT/PAT eventually to be able to access my servers from the internet, but I dont understand why the DSL modem (inside interface) doesnt respond to the ping. The outside (WAN) interface of my 2600 should be issuing the ICMP message (ping) and the DSL modem should only need to respond to it - the 2600 knows how to get it back to the 10.0.0.0 network. Obviously I am not understanding someting right. Could you (or anyone) explain?
 
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..i know its wierd...
...try this same setup with two routers..that end router will not know how route to that 10.0.0.0 subnet. it wont be in its routing table! it wont know automatically where 10.0.0.0 is just because it is directly connected to the 167.x.x.x.
...good luck

CCNP,CCSP,MCSE,Sec+,Net+,A+...
 
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Right after typing my first reply to your post I drove into the office and had to try our your suggestion. Of course you were absolutely correct - it works perfectly. It just seems so strange to me that the router doesnt inherently know how to pass packets between its interfaces. Now in hindsight I can see that this assumption is directly responsible for a heck of a lot of thrashing over this configuration. If you (or anyone else) knows where I could get a white paper or other technical article that explains this I would be most grateful if you would forward it to this thread.

Thanks very, very much for your help - I am off an running now with a 'real' router...
 
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...if you want to know more information about routing you probably need to do key word search in google like "implementing static route site:CISCO.COM"...this will only pull from cisco website..and they have a lot of tutorials. you just have to do some digging...there is no magic pill on how to learn this stuff..you just have to put some labs togethor..trial and error...

..but dont forget that suggestion about getting an adsl wic card. you can take that modem out of the picture..but you will still have to nat/pat..

..below is that wic on ebay..


..hope this helps...

CCNP,CCSP,MCSE,Sec+,Net+,A+...
 
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