Extending IP Range 2

[gwynfijones]

I have inherited a DHCP range of 10.10.10.0 - 10.10.10.255 with a subnet of 255.255.255.0 from a former employee. In his infinite wisdom he has not allowed for expansion. When i try to extend the range to 10.10.11.255 i get a messgage "THE RANGE IS EXTENDED LESS THAN THE SPECIFIED BACKWARD EXTENSION". As far as i can make out the additions have to be in increments of 32. This is so what is wrong ?

 

[pansophic]

Of course you are getting the error. Your netmask only allows for 256 IP addresses (255.255.255.0) and you are trying to implement 512 addresses. You have a few options here. One is to change the netmask to 255.255.254.0, which will allow you to use the entire 10.10.10.0 - 10.10.11.255 block as a single subnet. Another is to create a new block of DHCP addresses, 10.10.11.0 - 10.10.11.255 with a subnet mask of 255.255.255.0. If you choose the second option, you will need to set up a gateway to provide packet forwarding between the two subnets. This is frequently done by putting either a secondary address on the router, or by segmenting the network onto two separate interfaces on the router, each supporting one of the subnets.

There are advantages and disadvantages to both scenarios. An advantage to the first scenario is that it is simple, and requires almost no thought. The downside is that your network utilization is likely to be a little bit higher, because of the number of hosts that can "see" each other. 500 hosts is a lot of hosts on one subnet, but not unheard of.

A disadvantage of the first scenario is that you will have to log on to each of the statically addressed devices on your network and make sure that you have changed their netmask to match the DHCP address pool.

Of course, with the second option, you will increase the load on your router. But then again, the router and the DHCP server are the only things that have to be modified.

pansophic

 

[gwynfijones]

Thanks very much for the help