Gayathri wrote:
> interface Ethernet0
> ip address 10.X.X.X 255.255.0.0
> ip helper-address 10.X.1.X
> ip helper-address 10.X.1.Y
>
> The main reason we have 2 DHCP servers is for redundancy.
>
With both servers in the same physical LAN, you have redundant servers
but not redundant network paths nor redundant layer 2.
> Please note that they are independant of each other .
>
For a more robust redundant solution with true failover and incremental
updates, you might want to check out Cisco Network Registrar (CNR).
> Does this mean that , when the client is requesting, the router first
> forwards to the first DHCP server and since it is not getting a response ,
> is dropping it?
>
No, as far as the router is concerned, this is a very simple operation.
When a UDP-based broadcast is received on an interface with a helper
statement, the destination port is compared to the list of ones to
be forwarded. If it's one of those, then the destination IP in the
packet (255.255.255.255 or subnet broadcast) is overwritten by that
specified in the helper-address. The packet is then routed just like
any other. If the port type is DHCP/BOOTP then the router fills in
the giaddr field so the DHCP server knows the correct client subnet.
If there are two, three, twenty helper-address statements, then the
router just repeats all this for each in turn. The first DHCP server
in the list will likely get the request first, but which repsponse
actually comes back first is a horse race. DHCP client and server
code deals very gracefully with multiple responses (see the RFC).
Marty Adkins Email: [EMAIL PROTECTED]
Mentor Technologies Phone: 240-568-6526
133 National Business Pkwy WWW: http://www.mentortech.com
Annapolis Junction, MD 20701 Cisco CCIE #1289
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