Lack of IP Address

Unanswered Question
Feb 19th, 2008

Our head off we have 2811 router using class C IP Addressing. Five branches are connected through head off through lease line. Head Off LAN can use only 254 host now host are going to increase, how I can do this. Experts can u guide me.


I have this problem too.
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aijaz802 Tue, 02/19/2008 - 01:26


I hope that you are using private IP address.

Lets are using is ur LAN IP subnet..

On the router the gateway might be you are using ips from till total 254 hosts.

To increase the host range there are two steps I suggest..

1. Increase the subnet mask on the router from to this will increases ur hosts from 254 to 508. you will get additional block ips from till, gateway for these hosts is same old one You might need to change the subnets of the old hosts from to

2. Add a secondary IP address on the router where the present gateway ip present..


conf t

int fa0/x

ip add secondary

you can use this block of 254 hosts for the new PCs..

I hope it will help you...

Pls. rate if it helps..



netview69 Tue, 02/19/2008 - 19:50

Hi Aijaz,

2nd option is good I hv some Q?? We are using RIP so need to configure RIP for new network.


conf t

int fa0/x

ip add secondary

router rip


any thing else except this. For LAN we are using DHCP on server, so I think we need to configure new dhcp scope for & for new scope gateway is & DNS,WINS is series.

let me know I am right na.


ilnaiduccna Tue, 02/19/2008 - 21:02

Hi aijaz,

It may not good diverse.

As you told in 1 step by increase the router subnet mask from to then we can get additional block ips from till

Now my doubt is by increase the router subnet mask means change only? no need to any additional configurations.

In your second step by add a secondary IP add on the router where the present gateway ip present means is it IP/Subnet.

Can you clarify my doubt.



netview69 Wed, 02/20/2008 - 22:46

Ajiaz I am waiting for urs response. Pls reply me soon.


ergonullu Tue, 02/19/2008 - 01:38


There are few options but I need to know your IP ranges details

Besides if you do not have a chance for subnetting you might think about IP NAT Translation by creating new networks like I did but gotta be frank this needs a little bit proficency


shivlu jain Tue, 02/19/2008 - 20:51

as per my option if you are able to use the ist method then it wil be good. Because secondary ip is not prefereable always.




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