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New Member

3750 Switch Not Giving Dynamic IP's Out

I just hooked up 3 3750's, they are not stacked together as the cords aren't long enough. If I statically assign a machine an IP, it will go through but the dynamic addresses are not going through. I get a message on the machine that the DHCP server has timed out, and the DHCP server is fine.

Is there some setting that I am missing on the switch that enables the switch to do this?

Also, when I look at the switches via Cisco Network Assistant, the Admin mode is Dynamic Auto but the Operational mode is Static.

Thanks in advance for any help...

7 REPLIES
New Member

Re: 3750 Switch Not Giving Dynamic IP's Out

Hi,

Have you configured "ip helper-address" to send the DHCP query to DHCP server.

Senthil

Purple

Re: 3750 Switch Not Giving Dynamic IP's Out

Is the dhcp server on the same subnet as the clients ? You might have to post your config for any help..

Cisco Employee

Re: 3750 Switch Not Giving Dynamic IP's Out

Hi,

if the dhcp is in a seperate vlan, u'll need hepler address:

Ex: vlan2: dhcp / vlan3:data

Required Config:

interface vlan3

ip helper-address

Operational mode static access means theres only one vlan being forwarded on the link. in case you have only one vlan, its fine,else we need to setup link to allow multiple vlans as trunk link.

well,if its fine i.e if u actually have one vlan,so u should not need a helper address.

so if its multiple vlans,set up links as trunk s.

You can refer to www.cisco.com\univercd for switch config and command help.

and then enable helper address on the required vlans.

if it has to be a single vlans, post ur config, then i can check.

Let me know if it doesnt works :)

New Member

Re: 3750 Switch Not Giving Dynamic IP's Out

Thanks so much for your suggestions, however, it's still not working.

It is only one VLAN, and if you connect something directly to the switch, it will give out a dynamic address, but it is not giving them out to the computers that are connected via the port. This is very strange.

I put the old switches back in just so that people could work, and now they are doing the exact same thing. Grrr...

Purple

Re: 3750 Switch Not Giving Dynamic IP's Out

You should post your configs and blank out or substitute public ips and maybe we can figure out what is going on .

Cisco Employee

Re: 3750 Switch Not Giving Dynamic IP's Out

I would suggest you to post your configs for once. One reason that I can think is that particular port is also being used for span session, is that so?

Configs should help.

New Member

Re: 3750 Switch Not Giving Dynamic IP's Out

Are you running 12.2.(25) by any chance?

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