Hello!
I have the following config on my router LAN interfaces to allow use of two DHCP servers on other network:
ip helper-address 192.168.0.201 ip helper-address 192.168.0.202
Can you explain me how it works exactly, because I see two possibilities:
- The router "sees" the DHCPDISCOVER packet and forwards the packet to the 192.168.0.201, and if no DHCPOFFER comes back from the address, it forwards the packet to the second address - 192.168.0.202. Then, for example, DHCPOFFER arrives from 192.168.0.202 so the router forwards DHCPREQUEST to the 192.168.0.202 only.
OR
- The router "sees" the DHCPDISCOVER packet and forwards it to both addresses simultaneously. Then DHCPOFFER arrives from (for example)
I ask because my two dhcp servers are not synchronized, and there is a situation sometimes that one dhcp server gives the client an ip address already assigned by the second dhcp server. I know that dhcp servers should stay synchronized and they should know about each other address assignemnts. But I have no idea if the problem lies in the dhcp servers or wrong router configuration. I don't know the ip helper-address process in such detail.
Could you help me, please?
Regards, Tomasz Grzelak