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DHCP over Provider MPLS network

Unanswered Question
May 22nd, 2012
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Hi

Windows DHCP server is all working well at HeadQuarter.  Can Sales office  gets IP address from DHCP Server located in HQ.

Connectivity between HQ and Sales Office is over Provider MPLS Network


Thanks

ST

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Giuseppe Larosa Tue, 05/22/2012 - 07:53
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Hello Saquib,

generally speaking yes it is possible if the routers of the remote office are configured to act as DHCP relay agent


this means the use of ip helper-address on client facing interfaces on remote office router(s)


The HQ DHCP server needs to be configured with the DHCP pool(s) for the remote office.


The ip helper-address allows the router to convert a non routable DHCP request with a 255.255.255.255 destination to  a routable packet with IP destination = DHCP server IP address, source IP address = a router interface. Internally a field is filled with the IP address of the interface that received the DHCP request and it it used as a key to pick a free IP address from the correct DHCP pool on the DHCP server.

The answer (DHCP offer) is sent back to the router that will then propagates the reply out of the interface that received the request.


The presence of a L3 MPLS VPN or other service should not block the above process.( with the ip helper-address and so on)


Hope to help

Giuseppe

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