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Dhaval Dikshit
Beginner

DHCP limitation on cisco 3750 switches

Hi,

I want to clear following things regarding Cisco 3750 switch.

1. Can I configure Multiple DHCP pool on C3750?

2. Performance effect due to same?

3. Can I resrve IP addrese from DHCP pool for specific MAC address.

4. Can I Exempt IP address from DHCP pool ?

Please share useful link for same.

Thanks,

Dhaval Dikshti

1 ACCEPTED SOLUTION

Accepted Solutions
Peter Paluch
Hall of Fame Cisco Employee

Hello Dhaval,

1. Can I configure Multiple DHCP pool on C3750?

Yes, you can, provided that each DHCP pool is tied to a different IP network. You simply create multiple pools distinguished by their unique names, and assign each pool to a particular network using the usual network command.

2. Performance effect due to same?

Performance impact is negligible, as the DHCP is used only when stations acquire their IP settings. There would have to be hundreds, if not thousands of stations requesting DHCP communication in order for the performance impact to be measurable. With sensible lease times in orders of hours, you will not notice any increased load.

3. Can I resrve IP addrese from DHCP pool for specific MAC address.

Yes, that is possible, although the configuration is awkward. Check the following two documents (actually, it's just a single document with two sections relevant to your question):

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-68D87544-7C6F-48C9-9DFE-56F5B7E4A89D

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-BCEB43D4-8C44-4C86-BBAA-6B977196D35C

The configuration examples can also be found later in the same document.

4. Can I Exempt IP address from DHCP pool ?

Yes, you can. This is done using the ip dhcp excluded-address command in the global configuration mode (i.e. this command is not entered in any particular DHCP pool). More information can be found here:

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-9DFE5A79-4529-4DD9-BB7B-CB46C10E9ABE

Best regards,

Peter

View solution in original post

5 REPLIES 5
Peter Paluch
Hall of Fame Cisco Employee

Hello Dhaval,

1. Can I configure Multiple DHCP pool on C3750?

Yes, you can, provided that each DHCP pool is tied to a different IP network. You simply create multiple pools distinguished by their unique names, and assign each pool to a particular network using the usual network command.

2. Performance effect due to same?

Performance impact is negligible, as the DHCP is used only when stations acquire their IP settings. There would have to be hundreds, if not thousands of stations requesting DHCP communication in order for the performance impact to be measurable. With sensible lease times in orders of hours, you will not notice any increased load.

3. Can I resrve IP addrese from DHCP pool for specific MAC address.

Yes, that is possible, although the configuration is awkward. Check the following two documents (actually, it's just a single document with two sections relevant to your question):

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-68D87544-7C6F-48C9-9DFE-56F5B7E4A89D

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-BCEB43D4-8C44-4C86-BBAA-6B977196D35C

The configuration examples can also be found later in the same document.

4. Can I Exempt IP address from DHCP pool ?

Yes, you can. This is done using the ip dhcp excluded-address command in the global configuration mode (i.e. this command is not entered in any particular DHCP pool). More information can be found here:

http://www.cisco.com/en/US/docs/ios-xml/ios/ipaddr_dhcp/configuration/12-4t/config-dhcp-server.html#GUID-9DFE5A79-4529-4DD9-BB7B-CB46C10E9ABE

Best regards,

Peter

View solution in original post

Thanks Peter,

Most of my doubt are clear. Just want to know that how to configure PAC or WPAD string in DHCP?  Is it same option which we use in ASA ? i.e.

dhcpd option 252 ascii http://example/example.pac interface inside   

or its differant ?

Thanks & Regards,

Dhaval

Peter Paluch
Hall of Fame Cisco Employee

Hello Dhaval,

Specifying DHCP options in IOS is very similar: in each pool where the option is necessary, you use the following command:

option 252 ascii http://example/example.pac

Best regards,

Peter

Thanks a lot Peter.

Regards,

Dhaval

Peter Paluch
Hall of Fame Cisco Employee

Hi Dhaval,

You are welcome!

Best regards,

Peter