Cisco router - Possible to setup DHCP on same IP range as WAN IP?

[Over Clocker]

Hi guys,

I was just wondering if anyone knows:

Cisco 867VAE router

Is it at all possible to set it up so that it gives out DHCP on the same subnet as the fixed WAN IP? For us, whether selecting NAT or not, it will not allow us to offer out DHCP on the same range as the WAN port IP.

Thanks,

Mal

 

[the-evaluator]

Not on the same subnet but if your WAN IP is a /32 then you can create a range, say a /25 that is either above or below but not including that /32 WAN IP.

 

[GhostlyPea]

How is the WAN IP configured and what type of connection is it you're using? Ethernet - xDSL?

If so then create a BVI and chuck 2 interfaces (WAN & LAN) in the same bridge group. Give the BVI the IP/mask and apply your config to that. DHCP should work from there, some similar things but without the DHCP, but I see no reason why it shouldn't work

- GP

 

[matthab]

Not on the same subnet but if your WAN IP is a /32 then you can create a range, say a /25 that is either above or below but not including that /32 WAN IP.

I would do this but create a /30 on the wan interface between you and your provider. Then on the LAN network allocate the rest, I'm not sure if you can do reservations on Cisco routers. I think you have to create separate pools... Although depending on your subnet this can waist IPv4 space .

I would however assign your whole WAN subnet to the WAN network and then NAT through to a RFC1918 address. This reduces waist and also allows for multiple IP address's assigned to different services.

 

[the-evaluator]

I'm not sure if you can do reservations on Cisco routers. I think you have to create separate pools

Yeah, it's a separate pool for each reservation. Also the key is to use the client-identifier setting to identify the host, rather than hardware-address. Find the right value to use by looking at the output of 'show ip dhcp binding'