Posted on 2011-09-22
Last Modified: 2012-05-12
Hi, My Internet provider, provided a Netgear Router Model no: VMDG280 Via a coaxial cable.  The Netgear also has 3 Eth ports on it.

- I have connected my Cisco 837 router via a x-over cable to the Netgear router.
- My Cisco 837 has SDM 2.5 software running on it.
- I know how to Disable the DHCP on my Netgear router
- I have allocated temporarily an IP Address on same subnet as the Netgear just for the purposes of being able to access the Cisco 837 and I can successfully.

I wish to know how to allow the Cisco 837 via SDM 2.5 run Dhcp instead of the Netgear so that I can then 'TEST' and configure the box just for practice?

Can anyone advise?

Question by:mikey250
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LVL 18

Accepted Solution

jmeggers earned 250 total points
ID: 36583232
I suggest learning with the CLI.  If you're like most people, you'll find it more productive in the long run.

I can't tell you what to do with SDM, but here are the typical commands to run a DHCP server in IOS:

configure terminal
ip dhcp pool <name>
 network <x.x.x.x>
 default-gateway <x.x.x.1>
 dns-server <z.z.z.z>
 wins-server <z.z.z.a>

ip dhcp excluded-address <x.x.x.1> <x.x.x.z>

There are probably other options but those are the major ones.  Excluded addresses are for things like the default-gateway for that subnet, addresses you don't want to use for the pool because they're already in use somewhere else.  

If you really want to play with it, put Wireshark on a PC and sniff the packets so you can see the actual exchange. To do that, you'll need to use a true hub (not a switch) or SPAN ports on a switch to capture the traffic.  You can also debug ip dhcp on the router and see output from that.


Author Comment

ID: 36585667
Hi jmeggers,  Yes I know how to configure the DHCP via the CLI and successfully tried it via the SDM and it was successful by also adding dhcp config to the Cisco 837!!!!

After the above as not configured the other settings I lost my internet connection.?

I clicked on the LAN part to detect the Eth ports but it appeared to do a search and stop.

The connection that I was expecting to be detected on the Cisco 837 was the x-over cable for port 4 of the Cisco 837, but it did not!!

Saying that I've just now realised I should have 'Disabled' the Dhcp and removed 'mac' from the Netgear list then saved settings, then tried to detect the Port 4 on the Cisco 837.....

Dont know why I forgot that!!

Author Comment

ID: 36585696
I have software for 'Wireshark' but will use that later as just trying to understand be able to do the practical of making another router priority due to the way I've got it connected as my Cisco 837 has an 'ADSL' port and cannot use it because my Internet Provider has provided the 'Netgear router' which has a 'Coaxial' cable attached!!
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Author Comment

ID: 36586164
Hi jmeggers,  My Cisco router 837 is now set as the primary Dhcp as the 'Netgear router' that is directly connected to the internet is also 'Disabled'.

Qns1. My laptop that I plugged into the Cisco 837 Eth port is up and has been allocated an address via DHCP but I have no internet access - Why?

I mentioned previously that the 'LAN' tab on the Cisco 837 just searches but does not open up what ports are detected as this is what I think is the problem hence no internet connection on my laptop!!!!
LVL 15

Expert Comment

by:greg ward
ID: 36591327
please paste the output from show run
please remove all passwords.


Author Comment

ID: 36592018
Hi deepdraw,  I have not removed nothing yet as the only things set are the following:

The config to allow access to the Gui
Dhcp configured

- Bear in mind my direct connection to the internet is my Netgear router via a 'coaxial' cable, with 4 Eth ports
- The Netgear Dhcp has been disabled, although when I disconnect the x-over cable the Netgear router still has the ability to allocate IP Address.  After Disabling the Netgear and 'Apply' changes, I have not logged off the 'gui' or rebooted the router!!

- My other router is a Cisco 837 connected to the Netgear via a x-over cable
LVL 15

Assisted Solution

by:greg ward
greg ward earned 250 total points
ID: 36592567
dhcp sets up local ips and also the default gateway.
If the default gateway is not pointing at the netgear you have a problem.
to find out what is happening use ipconfig /all on a desktop/laptop
also check dns.
I would advise you configure the router from the cli as above, its easier for other people to assist.


Author Comment

ID: 36592958
Hi Greg,  ive attached 'cli' of Cisco 837 & host - 'ipconfig  /all'.

Author Comment

ID: 37326782
Hi experts if its ok I wish to come back to this thread at a later date as wish to resolve the last issue I had when trying to connect as a temporary measure, my Residential Netgear box, which is my direct internet connection, via my Cisco 837, just for the purposes of learning and configuring 'sdm', but the issue I had was that it would not give me an internet connection.

What I remember as my cisco 837 is not currently connected was that I think I was supposed to link an 'eth' connection or something within the 'sdm gui', as was connected via the 'eth' port of the cisco 837, but was not sure what I was supposed to do first as tried and failed.

Author Comment

ID: 37333857
Hi ive read through my comments again with more clarity and ive decided that the expert advice is enough for me to now close this thread.  thanks for your patience.

Author Closing Comment

ID: 37333861
sound advice.

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