April 28th, 2009, 06:57 PM
Packet Tracer and DHCP Configuration
I'm trying to teach myself how to set up and configure a LAN using packet tracer, but I am running into a problem. The server I designated for DHCP isn't assigning IP addresses. I attached two pictures below. The first is the Switch table so you can see there are no ips being assigned. The second is the server's configuration. Can someone explain what the problem is?
April 28th, 2009, 08:43 PM
Do you have a way to view the traffic going across? Can you see if your DHCP server is sending out DHCP offer messages or getting DHCP discover messages?
April 28th, 2009, 09:25 PM
There might be a way to do that, but I haven't figured it out yet. Does the configuration look okay on the server image?
Originally Posted by seack79
April 29th, 2009, 08:06 AM
You do have the DHCP service started and the address pool I think is setup right. Do you have to specify a range of IP addresses to lease out or does the device automatically assume a 10.x.x.x/24 network?
If so, it looks like all the devices are connected via the switch just fine. If you can, run wireshark on the DHCP server and see what packets are coming into it.
April 29th, 2009, 08:32 AM
Have you looked at either of the PCs you have connected to the switch? I can put pretty much the same configuration you have in Packet Tracer 5.1, tell the PCs to automatically receive an IP from DHCP, and they will show an IP assigned while the switch still shows <not set>.
Originally Posted by CallowAdmin
This makes me wonder if it is either a bug in Packet Tracer of it that table were supposed to be for the switch DHCP features. The latter is a big hard to test since the "IOS" available for the switches in Packet Tracer only includes a select number of commands.
April 29th, 2009, 10:05 AM
HAHAHAH, had to look at this one a few times to realize what's going on...
The switch ports will NOT have an IP address on them because they ARE LAYER 2 PORTS. Layer 2 is MAC address only, meaning you should take a look at the ARP table.
Some Cisco switches (including the 3560 you have listed there) can support advanced IOS images where you can basically give an interface an IP address and turn on "Layer 3" switching a.k.a. "Routing". Since this is not the case, all of your interfaces will have an IP address of <not set>.
However, you will want to put an IP address on VLAN 1 since it is your management VLAN (by default) and will allow you to remote into the switch to manage it.
Last edited by AdamPI; April 29th, 2009 at 10:09 AM.
April 29th, 2009, 10:22 AM
The switch needs no configuration since all ports are in vlan1. However you are looking at the switchports to determine if DHCP is working and the switchports and vlans are not set to get DHCP addresses so will not have anything. Check the PC's and see if they got an address not the switch.
April 29th, 2009, 11:49 AM
You have got to be kidding me, you never checked the PCs themselves?
Just fooling with you...
April 29th, 2009, 04:04 PM
I definitely checked the PCs. When I request an IP it says "DHCP request failed"
April 29th, 2009, 04:08 PM
So I manually set the IP and subnet on the server, and now it is assigning IPs. The thing is, the range is different than what I assigned. I said to begin with 10.148.5.1 and it is using 10.0.0.1
Why would this happen?
April 29th, 2009, 06:35 PM
This will happen (I think) if you don't have the proper subnet mask specified. You're using a class A IP address. If you don't specify a 24-bit mask (i.e., 255.255.255.0) it may default to an 8-bit mask since it's class A.
If you can, see if you can specify 10.x.x.x/24 or a subnet mask of 255.255.255.0
April 29th, 2009, 07:35 PM
That makes sense, actually. And now it works.
Originally Posted by seack79
April 29th, 2009, 09:07 PM
Eh, I get lucky every once in a while. Glad it's working.