2 DHCP Server for the same LAN

[hseakleang1]

I have two Layer3 switch, and configure as HSRP. I configure DHCP server on this two switches to provide IP for the same LAN. These two DHCP servers have conflict MAC address. How can i get rid of this problem? Can i configure DHCP server with priority?

[Markus Benz]

Hi

could you share the DHCP configuration?

Regards,
Markus

[Krishnendu AR]

Hello hseakleang1,

You can try sharing the DHCP pool between the two L3 switches.

For example if your subnet is 192.168.1.0/24, configure the DHCP pool 192.168.1.1 to 192.168.1.127 in one switch and configure the remaining IP as a DHCP scope in the second switch.

Krishna

[Ciscosianer]

Hello Krishnendu AR

since days I search this question, since I use the same DHCP principle!

Same networks on both switches!

However, the question remains open what happens when L3 Switch1 breaks away?

In this case, get the calculator in the first segment no IP or?
But there is no real redundancy?

[paul driver]

Hello

The problem i guess is you  both dhcp server active and they are also active for the same scopes-  you shouldn't do that

What you should do the split the dhcp between the two server so that one is providing half of the scope and the other is providing the other half.

R1
ip dhcp excluded-address 192.168.1.126 -192.168.1.254

R2
ip dhcp excluded-address 192.168.1.1 -192.168.1.125

Lastly for servers, they should have their ip address reserved anyway ( if to be supplied by dhcp) they should be negated from having their ip address changing.

res
Paul

[Ciscosianer]

Hello Paul,

on the server there is currently no fixed reservation for the phones.
There is only the pool !

I can not quite follow you, how could the config look so I can understand it?

Thank you for your feedback

[paul driver]

Hello 

The dhcp scopes are on the L3 switches correct?

So you need to reserve the ip address for any servers you wish to obtain dhcp allocation or exclude the server ip address from the dhcp scope so nothing else receives the same ip address.

You reserve them via the server mac- address:

example:

Server mac- address =3333.2222.1111
ip dhcp pool Server1

host 192.168.1.1 /24
client-identifier 0133.3322.2211.11
default-router 192.168.1.254
dns-server x.x.x.x
lease x x

res
Paul