1020 19 this picture shows the same as the last one

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Unformatted text preview: ne, but more detailed. The client sends out his DHCPDISCOVER message and both servers receive it. Then server 10.1.0.20 sends back his DHCPOFFER. In this offer there are the IP address for the client (Offered IP Address), subnet mask, server ID and also the lease length. 19 How Does It Work - 2 Thank you server 2 for the IP Address! Listen everybody: I use the information from this server, stop to offer! 3. IP LEASE SELECTION [DHCPREQUEST] DHCP Server 1 IP LEASE ACKNOWLEGMENT 4. [DHCPACK] DHCP Client (C) Herbert Haas DHCP Server 2 2005/03/11 20 After the client gets an offer from one server, he sends out an IP LEASE SELECTION [DHCPREQUEST] to tell the other server that he will accept the offer from server 2 and that the other servers can stop sending him offers. The DHCPREQUEST is also a broadcast. 20 How Does It Work - 2 DETAILED DHCPREQUEST 3. Source IP Address: 0.0.0.0 Dest. IP Address: 255.255.255.255 HW Address: MAC A Req. IP Address: 10.1.0.99 Server ID: 10.1.0.20 DHCPACK 10.1.0.10 4. Source IP Address: 10.1.0.20 Dest. IP Address: 255.255.255.255 Offered IP Address: 10.1.0.99 Client HW Address: MAC A Subnetmask: 255.255.255.0 Leaselength: 48h Server ID: 10.1.0.20 10.1.0.99 (C) Herbert Haas 10.1.0.20 2005/03/11 21 One important thing is the server ID in the DHCPREQUEST. This server ID tells the server from which the client gets his IP address that the client will take this offered address. After server 2 receipt the DHCPREQUEST he sends back the DHCPACK to acknowledgment this lease. 21 Bound DHCPACK (success) is send by the server who's offer was accepted Client receives the DHCPACK Client enters the BOUND state TCP/IP is completely initialized (C) Herbert Haas 2005/03/11 22 After the client receipt the DHCPACK (if all was successful) the client enters the BOUND state. After the client is BOUND TCP/IP complete initialized and the client is ready for data transfer. 22 DHCPNACK DHCPNACK (no success) will be send if Client tries to lease the previous IP address, but this address is no longer available Client’s IP address is invalid Client may have been moved to an other subnet (C) Herbert Haas 2005/03/11 23 If the client receipt a DHCPNACK message from the server something went wrong. Connection failure, IP address invalid, client move to an other subnet, etc can all l...
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This document was uploaded on 02/12/2014.

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