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New Member

config dhcp server on 2950

I want to config dhcp on 2950(the 2950 is a dhcp server),but i can't find the command "ip dhcp pool " ,don't it support dhcp?How to identify whether it support dhcp ? if it can't support dhcp, how to do with 2950 to support dhcp?

16 REPLIES
Hall of Fame Super Silver

Re: config dhcp server on 2950

kannis

The 2950 is a layer 2 switch and as such it does not support DHCP. If the2950 connects to a layer 3 device for intervlan routing you may be able to configure DHCP on the layer 3 device. But it will not work on the 2950.

HTH

Rick

Re: config dhcp server on 2950

Hi,

As per the 2950 configuration guide DHCP server functionality isn't not supported unless it's a 2955.

http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a00802c2f9e.html#wp1098054

HTH,

Sundar

Re: config dhcp server on 2950

Hi king,

i would not accept rburts & sundarz comments, because i have being using 2950 as DHCP server in my organization & its been working perfectly since Dec. 2005, infact even from the cisco forums i was getting the comments saying that 2950 doesn't support DHCP server. i am using cisco 2950T-24 & below are the working configuration

IOS name "c2950-i6k2l2q4-mz.121-22.EA6.bin"

ip dhcp excluded-address 10.196.1.51 10.196.1.254

!

ip dhcp pool URDU

network 10.196.1.0 255.255.255.0

dns-server 10.2.1.31 10.2.1.32 10.2.1.34

domain-name ueltv.org

default-router 10.196.1.252

lease 3

!

ip dhcp snooping

ip dhcp-server 10.196.1.250

hope this helps.

rate this post.

Re: config dhcp server on 2950

Hi,

The IOS Anand is running supports DHCP server configuration on a 2950, maybe because its an EI. Although the following document states that only 2955 can be configured as DHCP server - http://www.cisco.com/en/US/products/hw/switches/ps628/products_configuration_guide_chapter09186a0080648d88.html#wp1148254

But still I see here that 2950 can be configured as DHCP server.

So if you have an EI IOS then I think you can configure your 2950 as a DHCP server.

Refer the following link for configuring a DHCP server:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6b5.html#wp1000999

Hope this helps!

Regards,

AbhisheK

Please rate all posts!!!

New Member

Re: config dhcp server on 2950

King,

You most certainly can configure a DHCP server on your 2950. I have a 2950 sitting on my desk, that I use for a variety of router and switch testing and configuration, and I have a DHCP server running on it.

Also, do not believe the comments from those who say that you need to run the Enterprise Image in order to have the DHCP server code. I am using a c2950-24, which only supports the Standard Image. See below:

RMB_Deskswitch#sh ver

Cisco Internetwork Operating System Software

IOS (tm) C2950 Software (C2950-I6Q4L2-M), Version 12.1(22)EA4a, RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2005 by cisco Systems, Inc.

Compiled Fri 16-Sep-05 10:46 by yenanh

Image text-base: 0x80010000, data-base: 0x80562000

ROM: Bootstrap program is C2950 boot loader

RMB_Deskswitch uptime is 5 minutes

System returned to ROM by power-on

System image file is "flash:/c2950-i6q4l2-mz.121-22.EA4a.bin"

cisco WS-C2950-24 (RC32300) processor (revision G0) with 21039K bytes of memory.

Processor board ID FHK0702Y1TJ

Last reset from system-reset

Running Standard Image <================!!!

24 FastEthernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.

Base ethernet MAC Address: 00:0B:FD:5E:6E:C0

Motherboard assembly number: 73-5781-11

Power supply part number: 34-0965-01

Motherboard serial number: FOC07020QKA

Power supply serial number: DAB0701032M

Model revision number: G0

Motherboard revision number: A0

Model number: WS-C2950-24

System serial number: FHK0702Y1TJ

Configuration register is 0xF

RMB_Deskswitch#

RMB_Deskswitch#sh run

Building configuration...

Current configuration : 2333 bytes

!

version 12.1

no service pad

service timestamps debug datetime msec

service timestamps log datetime msec

service password-encryption

!

hostname RMB_Deskswitch

!

!

ip subnet-zero

ip dhcp excluded-address 192.168.0.10 192.168.0.254

ip dhcp ping timeout 2000

!

ip dhcp pool RMB_Deskswitch

network 192.168.0.0 255.255.255.0

default-router 192.168.0.254

domain-name xxxxx.com

dns-server 172.30.206.60 10.200.1.185

!

New Member

Re: config dhcp server on 2950

Now I am confused with your comments. I find my 2950 in company's lab(c2950-i6q4l2-mz.121-22.EA4.bin) supports DHCP server.But the customer's 2950(c2950-i6q4l2-mz.121-13.EA1.bin) don't supports DHCp server. what factor do determine whether 2950 support DHCP server? EMI or SMI?(How to identify EMI or SMI ?)IOS version?If I wan't make 2950 support DHCP server? how to do it? update from SMI to EMI ? update IOS ?

Re: config dhcp server on 2950

Hi,

What I can suggest is maybe you can copy the IOS from the switch which supports DHCP Server configuration to the other switch which doesnt support DHCP Server configuration!!!

But before you do that, I'd suggest that you check the compatibility of the switch with that particular IOS!!!

IOS Version of your company's 2950 - 12.1(22)

IOS Version of your customer's 2950 - 12.1(13)

Hope this helps!

Regards,

AbhisheK

Please rate all posts!!!

Silver

Re: config dhcp server on 2950

According to the IOS release note below. From 12.1(19)EA1, it supports DHCP server. This is why your customer's 2950 can't work.

However, all doc. stated that 2950 (either SI or EI) cannot support DHCP server, I believe there may be an error in Cisco doc that do not reflect the real situation. Or it is not official supported in 2950 but a bonus to the 2950 owner.

Hope this helps.

New Member

Re: config dhcp server on 2950

Jack,

We may have discovered another bit of info today. We configured TWO dhcp pools on a switch. However, only the first pool was giving out addresses. We could not get any addresses assigned from the second pool. Each pool was specific to a VLAN on the switch.

Perhaps the 2950 can only support one ACTIVE pool, even though multiple pools can be configured?

I couldn't find anything in the docs that even came close to describing what I was looking for.

Ron Buchalski

Silver

Re: config dhcp server on 2950

Hi Ron, I cannot test this feature due to no such equipment on hand. I believe there are two reasons :

1) The equipment itself does not support it;

2) The 2955 supports it but 2950 not

Can you try to activate the second pool and check again ?

Check below if it can help.

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6b5.html

Hope this helps.

New Member

Re: config dhcp server on 2950

Hi Jack,

I can't put this together again today, but I may be able to try it later this week.

After processing it yesterday, I came to the conclusion that it did not work because it is related to the number of active VLAN interfaces that can be configured on the 2950 (which is only one), and the fact that the working DHCP pool was giving out addresses in the subnet that was also assigned to the active VLAN interface.

What I had configured were two DHCP pools. The subnets for the two pools were defined and assigned to two different VLANs, and the upstream router had an FE connection with subinterfaces and dot1q encapsulation, assigned to those VLANs, and given the IP addresses of the default-router within each DHCP pool.

And, as I mentioned above, the only difference between the working pool and non-working pool is that the switch itself had a static host address in the 'working DHCP' subnet. I could try switching the host address of the switch to a static address in the 'non-working' DHCP pool range and see if the switch starts giving out addresses within that pool. That would confirm my suspicions about the one VLAN interface theory.

I'll post an update when I have a chance to test it.

Ron

Silver

Re: config dhcp server on 2950

Thx. for the info. and will wait for update.

New Member

Re: config dhcp server on 2950

Jack,

I tested DHCP server on my desktop switch today, and confirmed the following:

1) Multiple DHCP pools can be configured on a 2950 switch

2) A VLAN interface within the same subnet as the DHCP pool must be configured on the switch. Multiple VLAN interfaces (to match multiple DHCP pool ip subnets) can be configured

3) Only one VLAN interface can be active at any one time. The remainder of the VLAN interfaces will be Admin Down (by IOS)

4) Only one of the DHCP pools can be active at any one time. The pool that is active is determined by which VLAN interface is currently active

5) Only ports within the same VLAN as the active VLAN interface will be able to obtain an IP address from the locally configured DHCP pool on the 2950 switch.

I hope this helps others in the future, who are interested in using a 2950 switch as a DHCP server, to understand some of it's limitations.

Ron Buchalski

Silver

Re: config dhcp server on 2950

Thx. a lot for the report. It is good for others when we cannot find it from doc.

New Member

Hello ronbuchalski , 

Hello ronbuchalski , 

Thanks for the information ,, is there a specific IOS for dhcp in 2950 switches and if it is so what is the IOS for this feature ?   

New Member

You can check which features

You can check which features are available in IOS, CatOS, etc, and even compare features in two releases, here:

Cisco Feature Navigator

But as far as the 2950 supporting DHCP server, Feature Navigator does not show it.  So, as someone else suggested, maybe it's an undocumented 'bonus' feature, which unfortunately means it is also not supported.

But if you have access to the version that I tested, or one that others have successfully tested, then you should be able to enable DHCP server.

-rb

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