Argh. Tab and return doesn't work well in when posting through the web page....
Let me revise the last part of my message: If the interface (or sub-interface) looks like: int ethernet 4/0.42 ip address 10.0.1.1 255.255.255.0 ip address 10.0.2.1 255.255.255.0 sec ip address 10.0.3.1 255.255.255.0 sec Your scope logic in the DHCP server would look something like: scope_10.0.1.0: scope_10.0.2.0: primary-scope=scope_10.0.1.0 scope_10.0.3.0: primary-scope=scope_10.0.1.0 So when the DHCP packet arrived with the giaddr 10.0.1.1, it would match the "scope_10.0.1.0". The DHCP server would be able to determine that there are really three scopes which might apply to this request. Now, if one had secondaries on an interface (or sub-int) and wanted to vector a device (or particular types of devices) to a particular secondary, one needs to provide the DHCP server with more information in order to make the right scope selection decision. There are several places where this additional information might be found: - on the DHCP server. One might encode MAC addresses of the devices in the DHCP server and specify a "tag" value for this device. Scopes would also have tags and a device's DHCP request could only match a scope of their respective tags matched. Encoding MACs is nasty. - look at the DHCP information provided by the client. The client device might encode information in its DHCP packet which the DHCP server can use to help make a scope selection decision (see DHCP Option 60 and many others). - look at the DHCP information inserted by the router when the packet was relayed. In certain environments, the router will insert special DHCP options (see DHCP Option 82) which the DHCP server can use to determine the type of device and hence appropriate scope. Regarding the question about what happens if the DHCP server is on the same ethernet segement as your clients. I've never run this configuration. A couple of thoughts on this: * This must be a single network as I don't think you'd want to have the DHCP server physically connected to each ethernet segment where DHCP services are being provided. * As soon as one wanted to support a second interface (and thus different set of interface and DHCP addresses) you'd need to move to a model where there is a giaddr. Otherwise, the DHCP server would not have sufficient info to pick an appropriate address. * I'd move the DHCP server onto its own subnet and use helpering and the giaddr approach. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=58542&t=58498 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
