Two DHCP server in a network

[Rishi.WWN]

Hello Everyone,

Just want to know if there are two DHCP server in a network and I enable DHCP on a client machine.

1. client send the dhcp request broadcast mac and broadcast ip.

2.  both server will received the and provide the ip.

3. I client received the ip first from the sever it will keep and send the ack back to the server.

4. but how the second server know that my ip is not assign to any one. and what it will do.

[balaji.bandi · Accepted solution]

Most case you put the order in the config which DHCP Server 1 and DHCP Server 2 IP address.

In general deployment, if you have 2 DHCP Server the Scope will be split in to 2 DHCP Across, So respective DHCP Server can give correct address scope to clients.

[MHM Cisco World · Accepted solution]

PC will get IP from Server2, PC/Server then send ARP ask if anyone have this IP or not, if no reply then it will use IP if not then it will give use another IP.

[Richard Burts · Accepted solution]

There are some things in the original post that are not clear to me, especially 4). There are some things about the DHCP servers that we do not know which might impact our answers, are both servers local (in the same subnet/vlan/broadcast domain), does each server have a unique (non overlapping) pool of IP addresses? Basically this is what happens

- client sends out a single DHCP request with broadcast destination mac

- both servers receive the request and both servers respond to the client offering an IP address

- the client responds to one of the servers accepting the offered IP address

- the server who receives the response completes the process with the client of assigning the address, updating tables, etc

- the server which did not receive a response times out the request and knows that the address that it offered was not used and is available when a new request is received.

[Rishi.WWN]

Very Helpful, Thanks for your reply and Time.

[Richard Burts]

I am glad that our explanations have been helpful.  Thank you for marking this question as solved. This will help other participants in the community to identify discussions which have helpful information. This community is an excellent place to ask questions and to learn about networking. I hope to see you continue to be active in the community.