DHCP Configuration

[Anand Narayana]

Hi,

Below are the configurations of DHCP Server in 3550, it perfectly works fine & assigning the IP address across multiple VLAN's.now i wanted a setup in such a way that, i should not configure 3550 as DHCP Server, i wanted to make 2950 as DHCP Server, i mean we have got so many 2950 switchez, all switches are in same VLAN, but the PC's in every department are in different VLAN's. so i tried the option mentioned, but it doesn't work? where in do it in individual switch, it works, so how to proceed now. Thanks in advance & Happy New Year.

3550 (Working)

-----

ip routing

ip dhcp pool A

network 10.1.1.0 255.255.255.0

default-router 10.1.1.1

ip dhcp pool B

network 10.2.1.0 255.255.255.0

default-router 10.2.1.1

ip dhcp pool C

network 10.3.1.0 255.255.255.0

default-router 10.3.1.1

ip dhcp-server 10.1.1.1

ip dhcp-server 10.2.1.1

ip dhcp-server 10.3.1.1

ip dhcp snooping

interface gigabitethernet 0/1

description ***Connected to 2950***

switchport trunk encapsulation dot1q

switchport mode trunk

vlan 2

ip address 10.2.1.1 255.255.255.0

vlan 3

ip address 10.3.1.1 255.255.255.0

vlan 4

description ***Switch***

ip address 10.4.1.1 255.255.255.0

2950 (Not Working Configuration)

----

ip dhcp pool A

network 10.1.1.0 255.255.255.0

default-router 10.1.1.1

ip dhcp-server 10.1.1.1

ip dhcp snooping

interface vlan 4

ip address 10.4.1.1 255.255.255.0

interface fastethernet 0/1

switchport access vlan 2

switchmode access

spanning-tree portfast

interface gigabit 0/1

description ***Connected to 3550***

switchport mode trunk

2950 (Individual working Configuration)

----

ip dhcp pool A

network 10.1.1.0 255.255.255.0

default-router 10.1.1.1

ip dhcp-server 10.1.1.1

ip dhcp snooping

interface vlan 4

ip address 10.1.1.1 255.255.255.0

interface fastethernet 0/1

switchport access vlan 4

switchmode access

spanning-tree portfast

interface gigabit 0/1

description ***Connected to 3550***

switchport mode trunk

[mheusinger]

Hi,

in the *not wotking* 2950 example, the 2950 should provide IP addresses to which clients? Why is the DHCP server set to 10.1.1.1, when the Switch IP is 10.4.1.1?

Do you have IP connectivity to all the other switches?

A DHCP request from a PC is sent as a broadcast. When it reaches the DHCP server it will determine the proper pool from the interface it was received. So try to place the 3550 DHCP config completely into one of the 2950 switches. Also make sure not to have duplicate IPs.

In case direct broadcast access to the DHCP server is not possible you will need a DHCP proxy. This can be achieved by "ip helper-address 1.2.3.4".

Hope this helps

[Anand Narayana]

K fine, i think theoritically it works as what you have mentioned, but will let you after trying that in. Thanks

[Anand Narayana]

HI,

Thank you so much, as you said i have put them in the same VLAN on the switch, it really worked, but only disadvantage is, if a diff. PC is connected in the same 2950 switch, & i wanted that PC to obtain different IP address from different switch, i think it doesn't work, so in that case centralised L3 is advicesable, any how according to my requirement this will do. Thank U so much & Happy New Year.