Hi
I am trying to get my institute's network on track. I have finally got a network diagram of my insti and I will try to describe it for you.

We have a RF connection from an ISP which flows into a modem.

The modem is connected to a cisco router (model 1721) having two ethernet ports,

Etho: ip: 203.200.166.50 Netmask 255.255.252.0

eth1: ip: 192.168.10.1

This router feeds a gateway again with two NICs

eth1: 192.168.10.2 Netmask 255.255.255.0

eth0: 192.168.11.250 netmask 255.255.255.0

This gateway is connected to a p2p network with static IPs (including wireless access points) directly connected to this PC using hubs. this PC uses Linux and we primarily use it as a proxy (Squid) and content filtering (Dansguardian)

THERE ARE NO OTHER ROUTERS PRESENT ALL COMPUTERS ARE CONNECTED WITH HUBS AT SPECIFIC LOCATIONS. THESE HUBS DO NOT HAVE AN IP

We now have a problem with respect to number of IPs as we need to accomodate around 100 more computers and i have no IPs left?


The fundamental question is which is the easiest way to get these IPs for the new computer,

Secondly we want to get a client server system in place and want to have a DHCP server, to be augmented in future with other servers for mail, file sharing etc.

I have a Ubuntu (6.06) box and have tried a few experiments.

1. Created a DHCP config the config is given below
# A slightly different configuration for an internal subnet.
subnet 192.168.10.0 netmask 255.255.254.0 {
range 192.168.10.3 192.168.10.250;
option domain-name-servers 202.54.1.30, 202.54.9.1;
option domain-name "iiswbm.edu";
option routers 192.168.11.250;
option broadcast-address 192.168.11.255;
default-lease-time 600;
max-lease-time 7200;
}

I also changed the netmask of the gateway to 255.255.254.0 and also of the DHCP server and client.


A machine next to the DHCP server is able to aquire an address but is unable to ping the gateway or the router.

A machine in a different room is not able to get the address at all.

Even in a fixed IP scenario a machine in a differnt room from the server is unable to ping the router (192.168.10.1) but a traceroute flashes this number.

My gut feeling says there is some problem with the router's config (192.168.10.1) I have no idea gow to change the parameters in a Cisco 1721 router.

Can u suggest two things.

1. A quick fix solution (any method ) to get 100 additional IPs

2. a long term solution involving DHCP ( preferrabley a step by step recommendation)

Thanks
Vijay

You probably ought to switch to using 10.0.0.0/8 range, which is reserved for internal use just as 192.168.1.0 is, and gives many IPs and subnets. We migrated to a series of subnets based on 10.0.0.0 when we started to run out of IP addresses due to rapid growth.

It sounds like your existing network infrastructure needs to be redesigned to accommodate a changed set of requirements. Having been there, I'd strongly advise you to avoid any kind of quick fix at this point.

Push for training on TCP/IP or network design, which really helps with the complexities of TCP/IP, and then spend a bit of time planning it all out. Don't hesitate to get someone else in with experience of networking to advise/consult. If your management want you to support Cisco routers, WAPs etc. and add 100 more computers to the network then they should be prepared to make the necessary investments. If not then you should really consider your position.

thanks for ur reply
unfortunately we need a quick fix right now and then we can follow the training route,the management needs a quick fix and we actually have very little choice

thanks
vijay

well perhaps u can redesign ur network by removing the static ip scheme from the peers and hence run a dhcp server on the gateway... u can connect a computer to the gateway and then run dhcp on that newly attached system... moreover try to look at the need and not the IPs...redefine ur requirements and goals

Yes, he needs to replace the address range for his internal network. He can use DHCP to assign numbers from that range to the clients. The gateway and WAPs need to be assigned new IP addresses in the same range. Which means that once he starts changing the numbers the network won't work until the process is complete.

To be clear - the DHCP service can be on any system, not just the gateway. The key thing about DHCP is that there must be only one DHCP service on the network.

vj2k:

From your description, it sounds like 192.168.11.0 is for your internal network, but your DHCP config uses 192.168.10.0, so I'm not quite sure. Neither range is probably going to be large enough.

Ideally, pick a 10.0. range, such as 10.0.2.0/22 (255.255.252.0). Assign 10.0.2.1 to the gateway interface, 10.0.2.2 for the DHCP service. Reserve 10.0.2.3 to at least 10.0.2.50 for servers, WAPs and other things that need static IP addresses so that they are separate from the DHCP addresses. Configure the DHCP service to provide addresses from 10.0.2.51 (10.0.3.254 is the maximum for this range). 10.0.3.255 is the broadcast address.

You may find this useful for working out IP addressing:

http://jodies.de/ipcalc

(Edited for clarity.)