CCNP - DHCP Assignment

Author

DHCP Assignment

ruiner20

2001-12-13, 3:40 am

Okay, a little background on my problem:

I bought some routers off ebay and of course they contained minimal flash/dram, etc. so I've been in the process of upgrading them. I finally get the 2514 up to spec and have it running 12.2(6) IPfw IOS (not enough dram for the IPfw plus IPsec56) but anyway... now I need to assign an IP to my e0 interface via a dhcp server at my local cable provider. My cable modem is hooked into my 1924-EN switch and provides all the computer on the switch with IPs via the cables DHCP server. I need to get it to assign my e0 interface on my router an ip. In interface configruation mode, I've tried 'ip address dhcp' and 'ip address dhcp hostname <my cable provider's dhcp server ip>' and when I sh run or sh int e0 all it says for the ip is this: "Internet address will be configured by dhcp server". Will it? It never seems to happen. What am I doing wrong? Looking through my CCNA books, I see nothing on DHCP configuration for interfaces.... aaaaaaaaaagh. Sorry for the long post. Im on my last nerve. Thanks to all of you fellows nerds out there

Ruiner, A+, N+, CCNA

ruiner20

2001-12-13, 8:57 am

Small update.

This morning I played around with IOS a little and figured out what I was doing wrong but it still won't work.

In global configuration I used 'ip dhcp-server <my dhcp server>' to set the dhcp server for it to use. Then I issued "ip address dhcp" on my e0 interface but it still won't give it an IP!

What is wrong?

Ruiner, A+, N+, CCNA

haseeb_eng

2001-12-13, 9:01 am

use helper address i hope this will work

strikeattack

2001-12-13, 3:19 pm

quote:
use helper address i hope this will work

IP HELPER-ADDRESSES won't help because you still will not be able to give the FE interface an address. For the router to even "speak" to the internet, it will need an IP address. However, assuming you can get the DHCP address to work, you may be able to forward your nodes BOOTP DHCP broadcasts.

If you use your router to setup a new private subnet, how will remote nodes be able to respond to your privately addressed subnet? If you address internally as 10, 172, or 192, anything you can get a packet to will not know how to respond.

If it were MY NETWORK, here is what I would do.
Plug your cable modem into a hub. This is your DMZ/DHCP hub. Anything plugged into this hub will be on the Internet.
Build a multihomed Proxy server. Place one interface into the DMZ hub, and the other one to a nice Cisco switch. The Cisco switch, is of course, your LAN switch. Plug both routers into the Cisco LAN switch. Enable routing between the two. Place half of your nodes in Subnet A and half in Subnet B. Plug them into the Cisco switch. Even though they are plugged into the same switch, they will need to go through the routers to be able to talk to eachother. The Proxy servers are acting as your firewalls and are the only physical devices that connect your LAN to the Internet.

ruiner20

2001-12-13, 3:39 pm

I already have the cable modem hooked into the switch via a cross-cable, any node hooked into it gets to access the internet via the cable modem. I'm not trying to set-up a vpn w/ nat or anything right now. I'm simply trying to get my dhcp server to assign my e0 interface an IP

It can get to the dhcp server, I know that. I manually assigned the e0 interface an IP off the brick of my cable modems IPs on this subnet I am on and it was able to communicate with this local subnet, that is how I transferred the new IOS via tftp to it. But of course it would not speak to any computers outside this subnet. Really, it all just comes down to this: At this point, I just want the dhcp server to assign an IP to the router's e0 interface, that is all. The router can access the cable modem, that has been determined. The dhcp server just won't assign it an IP for one reason or another. help

Ruiner, A+, N+, CCNA

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