Superscope IP Helper
in [Cisco]
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From: Joel on 9 Jul 2006 23:26 Hello, Our 10.1.2.X subnet has depleted all available IP addresses. I created a secondary IP on our 1841 router (IOS 12.4) of 10.1.6.X. I'm going to create a superscope on our Win2k DHCP server (10.1.2.X) to distribute IP addresses from the .2.X and the .6.X subnets. I have assigned and tested a few static .6.X addresses and they seem to work fine. Do I need to add an IP Helper command to have the DHCP broadcasts from the secondary IP forwarded to the DHCP server? Can you recommend any other things to look for or consider before implementing this? Thanks, Joel
From: Merv on 10 Jul 2006 07:34 > Do I need to add an IP Helper command to have the DHCP broadcasts from > the secondary IP forwarded to the DHCP server? Only one ip helper command per DHCP server is required. > Can you recommend any other things to look for or consider before > implementing this? The DHCP relay agent will insert the PRIMAY IP address of the interface that the DHCP request was recived on. So the DHCP server configuration must take this into account when configuring the scope. You might want to think about moving to a new block where you can have two contigous blocks ...
From: Joel on 10 Jul 2006 10:39 Merv wrote: > The DHCP relay agent will insert the PRIMAY IP address of the interface > that the DHCP request was recived on. So the DHCP server configuration > must take this into account when configuring the scope. You might want > to think about moving to a new block where you can have two contigous > blocks ... Merv, We will be moving to a contiguous block in the future. For now I need to implement this solution to keep us going. You said "The DHCP relay agent will insert the PRIMAY IP address of the interfacethat the DHCP request was received on". So if the DHCP request is received on interface is 10.1.2.1 and the secondary is 10.1.6.1 any requests received from the .6 subnet will cause the DHCP relay agent to be 10.1.2.1? If my clients can use either subnet does this matter? Does this happen without any configuration changes to the router (no IP helper)? Thanks for your reply. Joel
From: Merv on 10 Jul 2006 10:49 > So if the DHCP request is received on interface is 10.1.2.1 and the > secondary is 10.1.6.1 any requests received from the .6 subnet will > cause the DHCP relay agent to be 10.1.2.1? That is correct. The relay agent will insert 10.1.2.1 into the GI address field of the DHCP request. Your DHCP server uses this info to know what DHCP scope to allocate from. So all the magic of using the second block must be configured on your DHCP server. > If my clients can use either subnet does this matter? probably not. > Does this happen without any configuration changes to the router (no IP > helper)? no changes given that you already have an ip helper command configured on the router interface in question.
From: Joel on 10 Jul 2006 10:59
Thanks! I'll be implementing this tonight when our office closes @ 12AM :( |