Hot standaby DHCP between two 2012 servers with (Cisco switch) ip helper addresses pointing to both, but how to control which DHCP server replies since they both get the message from ip-helper?!?
If we were to setup two 2012 DHCP servers as a hot-standby scenario (see article below) we would also have to point the Cisco switch IP helper address to both servers and then both would get the unicast or broadcast message through the switch when a client (desktop) looks for an IP, because if we do not then the standby DHCP would never be notified of address needs when the active one goes down. However, if we do then what mechanism is in place to prevent both DHCP servers from replying? Would they consult each other first or how would that work, because if they both reply then it isn't standby, but rather load balancing which is not what we need. Pretty sure someone has tried this and made it work. As always very much appreciating all insights and time. Cheers
https://community.cisco.com/t5/other-network-architecture/multiple-ip-helper-address-on-a-single-interface/td-p/404497
http://thesolving.com/server-room/how-to-configure-dhcp-failover-on-windows-server-2012-r2/
https://community.cisco.com/t5/other-network-architecture/multiple-ip-helper-address-on-a-single-interface/td-p/404497
http://thesolving.com/server-room/how-to-configure-dhcp-failover-on-windows-server-2012-r2/
Soulja
The switch will forward the request to both helper address, so the end host will use the address from the first server to respond.
Yeah, it's not even load-balancing as there is not a mechanism present to determine how many or what percentage requests go to which server.
ASKER
Thanks but can you elaborate a bit... before you said that "The clients will get their addresses from the first ip helper address. If for some reason that helper address doesn't respond. It will then be sent to the second helper address." now you say that both get it and the end host determines it... I am bit confused... So desktopA needs an IP lease and sends out the request... the cisco switch sees it and sends it to both DHCP1 and DHCP2 ... so are you saying that because DHCP1 is the primary in the standby setup it will service the request (presumably it has some sort of heart beat that tells DHCP2 that it is not needed) and DHCP2 only jumps in if DHCP1 does not respond???
ASKER
"it's not even load-balancing as there is not a mechanism present to determine how many or what percentage requests go to which server. " what about on the windows DHCP side... I understand that the switch is merely the medium that carries the message/request for a lease...
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I agree with DrDave. The load balancing would need to be handled by the servers themselves. Not the switch. I removed my first comment after rereading the question.
ASKER
Thanks.