Solved: Catalyst 2960S + DHCP

rwankyoto · ‎08-31-2012

Hi all,

I'm actually not very knowledgeable about switches, but I've tried to find a solution to my problem in the various manuals and have been unsucessful.

I am administering a Catalyst 2960S switch and I would like to connect several computers to it. Some of those each have a static IP address. For a few of them, I would like the switch to dynamically assign an IP address to them via DHCP. Is the switch capable of doing this? If so, how can I do it?

I tried looking through Cisco Network Assistant and I couldn't find it. Some web pages have suggested I telnet into the switch and issue commands like "ip dhcp ?" to see what commands are possible. I can telnet in and if I type but I get an "Unrecognized command" for both "ip ?" and "ip dhcp ?". This makes me think I'm reading the wrong web pages.

I'm completely lost. Any pointers would be appreciated! I did come across the term "DHCP snooping". It seems relevant, but very difficult for me to grasp. Is that what I should be reading?

Thank you!

Ray

Reza Sharifi · ‎08-31-2012

Hi Ray,

Once you get this prompt:

Switch>

than you need to type

enable

it there is password it will ask for it if not you will see this prompt

Switch#

now you can type config t

Let me know

HTH

View solution in original post

Reza Sharifi · ‎08-31-2012

Hi Ray,

Have a look at this post:

https://supportforums.cisco.com/thread/140131

HTH

rwankyoto · ‎08-31-2012

Hi Reza,

Thank you for the prompt reply!

I've seen replies such as that before during my Google search. However, I'm not sure how to get to the part where I can enter commands such as "id dhcp ...".

When I telnet into the switch, commands such as that do not work (as I mentioned in my original post). Do I need to do something before issuing the commands mentioned in the link you posted?

Ray

Reza Sharifi · ‎08-31-2012

Hi Ray,

Once you are at the switch via telnet try this:

config t

ip dhcp pool

HTH

rwankyoto · ‎08-31-2012

Hi Reza,

That doesn't work for me...I still must be doing something wrong. This is what I get:

-----

Connected to XXX.XXX.XXX.XXX.

Escape character is '^]'.

User Access Verification

Password:

Switch>config t

^

% Invalid input detected at '^' marker.

Switch>ip dhcp pool

^

% Invalid input detected at '^' marker.

Switch>?

Exec commands:

<1-99> Session number to resume

access-enable Create a temporary Access-List entry

clear Reset functions

connect Open a terminal connection

crypto Encryption related commands.

disable Turn off privileged commands

disconnect Disconnect an existing network connection

enable Turn on privileged commands

exit Exit from the EXEC

help Description of the interactive help system

lock Lock the terminal

login Log in as a particular user

logout Exit from the EXEC

name-connection Name an existing network connection

ping Send echo messages

rcommand Run command on remote switch

release Release a resource

renew Renew a resource

resume Resume an active network connection

set Set system parameter (not config)

show Show running system information

...

-----

Am I in the right menu? Is the ability to change configurations via telnet turned off and I have to turn it on somehow? I'm telneting in remotely to its IP address. Should I be connecting a cable directly to it and trying that instead?

Thank you for your help!

Ray

Reza Sharifi · ‎08-31-2012

Hi Ray,

Once you get this prompt:

Switch>

than you need to type

enable

it there is password it will ask for it if not you will see this prompt

Switch#

now you can type config t

Let me know

HTH

rwankyoto · ‎08-31-2012

Hi Reza,

Ah! That worked! Thank you for literally hand-holding me... I kept thinking I need to telnet in differently (i.e., via a cable while sitting next to it).

I'm going to configure the DHCP later when I am physically next to the switch so that I can reset it if I make a mistake. I will let you know if I am stuck.

But I have one quick question. In the menus, I can use "?" to find out what a command does. i.e, "configure ?" Is there a PDF document on Cisco's web site that explains each command. For example, the discussion you first showed me said I should type these commands:

ip dhcp pool test

network 192.168.50.0 255.255.255.0

domain-name cisco.com

default-router 192.168.50.1

dns-server 192.168.50.2

lease 4

Is there somewhere that explains to me what the above means. (I *guess* it means to set up a DHCP pool for 192.168.50.0/24 with the cisco.com domain, etc.) But is there something I can look at that explains the commands better? Or a term to Google for that is the name for this configuration method/"program"?

Thank you for your help (and prompt replies!)! I've been stuck on this for days...

Ray

Reza Sharifi · ‎08-31-2012

Hi Ray,

Glad to help

The best place for this type info is the configuration guide. It will go step-by-step and explain each command.

Also, as you have already found out, ? in Cisco IOS is your friend. If you are not sure just type ? and the IOS will give all the keyword that could added next for example after you type config t type ip dhsp and than a ? you will see the rest of the options

here is an example

Switch# config t

Enter configuration commands, one per line. End with CNTL/Z.

Switch(config)#ip dhc

Switch(config)#ip dhcp ?

aaa Configure aaa attributes

binding DHCP address bindings

bootp BOOTP specific configuration

class Configure DHCP classes

conflict DHCP address conflict parameters

database Configure DHCP database agents

excluded-address Prevent DHCP from assigning certain addresses

limit Limit DHCP Lease

limited-broadcast-address Use all 1's broadcast address

ping Specify ping parameters used by DHCP

pool Configure DHCP address pools

relay DHCP relay agent parameters

route Specify the type of routes for clients on

unnumbered interfaces

smart-relay Enable Smart Relay feature

snooping DHCP Snooping

subscriber-id Global subscriber-id configuration

use Configure use of certain parameters during

allocation

Switch(config)#ip dhcp

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/configuration/guide/swdhcp82.html#wp1320930

Also, for what you are trying to do you don't need to be sitting close to the router or switch you can easily configure it using telnet. You also don't need to reboot the switch after configuring the DHCP pool. Just follow the example in the link I provided and you should be fine.

HTH

Reza

rwankyoto · ‎09-06-2012

Hi Reza,

Thank you for your help and sorry for not getting back to you. I was pre-occupied with something else the last few days.

However, I got back to it and was unsuccessful. I noticed the original link that you sent to me was from a 2006 posting. Could the instructions be out-of-date?

These are the commands I issued:

(config)# service dhcp

(dhcp-config)# ip dhcp pool test

(dhcp-config)# network ...

(dhcp-config)# lease ...

(dhcp-config)# address 192.168.50.1 hardware-address ...

(dhcp-config)# ^Z

Doing "show ip dhcp binding" tells me that the pool seems to have been set up correctly. (The "type" is set to "Manual"; I'm not sure if that's the problem.)

Neither "ip dhcp snooping" nor "interface vlan 1" seem to work, so I've done nothing with that. And I don't know what the "default router" should be.

On this switch, a few ports are static addresses; on another set, I would like DHCP to assign addresses to them. I made them into separate VLANs. But I tried them all on one VLAN or on two separate VLANs and neither worked.

I also found the "IOS IP Addressing Services Command Reference" which explains the commands, but doesn't tell me what I could be missing. I feel like I'm one command away from getting it working; I just can't tell which command is it. :-)

Thank you for your help!

Ray

Reza Sharifi · ‎08-31-2012

Also, navigate the command reference guide for the 2960 series switches. It has all the commands you need with definitions

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_55_se/command/reference/2960_cr.html

HTH

Reza