Is it possible to have multiple DHCP Servers in a Single VLAN ?

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Dec 12th, 2009
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Hi,


I have one 4500 Core switch  and currently  have one DHCP Server .


But now the client requires one more DHCP Server in their network for redundancy or Failover in the same VLAN.


Is it possible to have multiple DHCP servers in a single VLAN ??




Pls advice..


Thanks ,


Mahesh

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ohassairi Sun, 12/13/2009 - 00:19
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yes it is possible.

the first that will answer will offer the IP address.

but in order to avoid ip conflict devide your IP scope in 2 parts :

for example if you have the range 192.168.1.1 ---> 192.168.1.254 then give server 1 the scope: 192.168.1.1 ---> 192.168.1.128 and server 2 :

192.168.1.129 ---> 192.168.1.254

or try to see if you can form a DHCP server cluster.


think also about implementing DHCP snooping to avoid DHCP attacks

Magesh G. Sun, 12/13/2009 - 01:03
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hi ,


thanks for the reply...


If we have multiple vlans in the network.. is there any changes to be done to VLAN interface config in my L3 switch ?


currently i have one ip helper address < dhcp server 1>  configured on the vlan interface .



Please revert.


Thanks ,

Jon Marshall Sun, 12/13/2009 - 02:10
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magesh2005 wrote:


hi ,


thanks for the reply...


If we have multiple vlans in the network.. is there any changes to be done to VLAN interface config in my L3 switch ?


currently i have one ip helper address < dhcp server 1>  configured on the vlan interface .



Please revert.


Thanks ,


Yes, you will need to add a second "ip helper-address x.x.x.x" command under your L3 vlan interfaces for the 2nd DHCP server.


Jon

vvasisth Sun, 12/13/2009 - 02:49
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yes you can have multiple dhcp servers for a vlan.

and the ip helper command is used to just convert the broadcast packet and send it as a unicat packet to the ip add defined in the command this command is mostly used when you have the dhcp server in a diff vlan.

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