DHCP Relay Packet Internet Tour

I. Overview:

The second layer of many experiments with GNS can not be simulated, IOU most of the only command can not see the effect, very easy to have the opportunity to log into the rack to do the experiment, did the DHCP snooping experiment, found Cisco router if as a DHCP server, must be configured IPDHCP relay information Trusted, otherwise the client will not be able to obtain the IP address, if you want the DHCP server to use Windows 2003, then add the 2003 DHCP service to the logon rack, but find that the DHCP service is not available, query the system log, Because this is in the workgroup 2003 with a domain control, it also ran DHCP, a mountain can not two tigers, encounter the genuine DHCP, my team's DHCP can only stay on the side.

After instructions, domain control can not let me log in to test, and the server does not allow the installation of virtual machine software, during the attempt to modify the test server subnet mask, no effect, if you want to borrow external DHCP to do the test, the following is a few tests:

A. Virtual machine (DHCP server) + host port forwarding +gns test

B.ezvpn dial-in + Test Server port forwarding + connecting rack test

C.DHCP server at the same time VPN server, PC1 dial vpn+gns, directly using the routing method test

D. Virtual machine (DHCP server, VPN server) + host port forwarding (simultaneous dial-in VPN) +gns test

Two. Virtual machine (DHCP server) + host port forwarding +gns test:

A. Test results:

---success

B. Test topology:

C. Configuration Description:

①PC1 is actually a host, configured with UDP port forwarding

② the port address of the router relay agent is the same as that of the host, because the DHCP server returns the packet based on the address of the DHCP relay in the DHCP unicast packet without looking at the address of the UDP three-layer header that reached it

③ Port forwarding requires two directions because of the characteristics of the DHCP server back pack

④R2 is configured with static NAT because of the need to ensure that UDP port forwarding, the data back to the relay proxy port address