cisco switch 3750 configured to work as dhcp server

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Aug 31st, 2007
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hi, i am facing problem in my LAN which has about 1000 desktops. i have configured dhcp on my cisco catalyst 3750 switch. this switch is connected to 15 departmental cisco 2950 series swithes. now we are facing day by day problem of client machines are not getting ip from the switch which is working also as dhcp server. Yellow icon comes on task bar and message shows "limited or no connectivity". i have to go for the static ip for those systems. this problem is increasing day by day. i am attaching you the switch configuration detail with this mail.

thanks in advance for your efforts.

ashok gupta


[email protected]

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JORGE RODRIGUEZ Sun, 09/02/2007 - 14:38
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Hello Ashok,

You have 1000 users, and in your config you only one dhcp scope as subnet that will only provide for 254 addresses. How do you manage to have the rest of the 750 users to have dynamic IP addresses when only you have one subnet.

I would recommend to go over the bellow links which will provide you with more detailed information in configuring full IOS DHCP services in routers, I don?t believe the switch model you have will provide full DHCP services.

For that amound of users I would recommend to implement DHCP services at your core router which also does your intervlan routing for other subnets in your network.

Couple of links bellow as references:

1-Cisco IOS DHCP config guidelines and supported platforms.

2- You may also check software advisory tools and check for IOS HCDP features in specific platforms by looking in "search by features " on this link, but most importantly is to go over the 1st link on IOS DHCP implementations and guidelines and suported platform.



Edison Ortiz Sun, 09/02/2007 - 15:22
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2^16 provides for 65534 host addresses.

2^8 provides for 254 host addresses.

Edison Ortiz Sun, 09/02/2007 - 15:34
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Your config looks good. Can you turn 'debug ip dhcp server packet' on the switch while a workstation is trying to obtain an IP ?

Do you see the request coming in ?

glen.grant Mon, 09/03/2007 - 16:51
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Also verify all client ports on all your switches are setup with portfast turned on , otherwise the clients can timeout before getting an address . If they are 2950's you can use the switchport host command to turn portfast on and channeling and trunking off for those ports .


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