I have installed dhcp-server on ubuntu. And server is providing ip address to clients(Window machines) but not default-gateway but I have another network in my network and same configuration and same dhcp-server provides every information. Thanks for any help.

Sorry, but if they're the same, then they'd WORK the same way. There has to be some difference.

Ubuntu forums has addressed this before. Have you compared the dhcpd.conf files between the two servers? And what version of Ubuntu are you using on them?
https://help.ubuntu.com/8.04/serverguide/C/dhcp.html

Thanks for reply. Basically I have only one server and two different network, and dhcp server send every information to clients on one network while on another network its send only ip and network mask not default gateway. And I have checked the dhcpd.conf file the configuration for both network is same. I have problem in network 192.168.2.0/24

option domain-search-order code 119 = string;

default-lease-time 86400;
max-lease-time 172800;

authoritative;
always-broadcast on;

log-facility daemon;

#local-address 192.168.1.5;

subnet 192.168.1.0 netmask 255.255.255.0 {
option domain-name "office.com";
option domain-search-order "office.com";
option domain-name-servers 192.168.1.5;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option ntp-servers ntp.ubuntu.com;
option netbios-name-servers hello.office.com;
option netbios-dd-server hello.office.com;
option netbios-node-type 8;
option routers 192.168.1.5;
option ip-forwarding off;
}

subnet 192.168.2.0 netmask 255.255.255.0 {
option domain-name "office.guest";
option domain-search-order "office.guest";
option domain-name-servers 192.168.2.5;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.2.255;
option ntp-servers ntp.ubuntu.com;
option netbios-name-servers hello.office.guest;
option netbios-dd-server hello.office.guest;
option netbios-node-type 8;
option ip-forwarding off;
option routers 192.168.2.5;
range 192.168.2.100 192.168.2.200;
}

Your original question and this follow-up are hard to understand.

Ok, you have one DHCP server. Great....so exactly WHAT isn't working correctly? The default gateway? IP Addresses? If you've got things split up on your network, are they getting the right IP address range, or is everyone going on ONE subnet?? How are you delineating the two subnets?

Hey Sorry for confusion. I have one Ubuntu server(This is my main router). I have installed dhcp-server and BIND on it and I have two different network 192.168.1.0/24(its for internal LAN) and 192.168.2.0/24(its for external wireless N/W). Now the dhcp-server send dhcp info to internal client with correct info and I have same configuration for another n/w. The dhcp-server send info to external wireless client also that is correct but not sending default-gateway ip address into info.

N/W topology:

Internet->Ubuntu Server(Dhcp server)--1. Internal LAN 192.168.1.0/24
2. Wireless AP(Which is just use for passing traffic) --> External Clients

If try to connect to internet through the Wireless AP I am getting IP address, DNS server Name ... everything is correct but I am not getting my default router address which is Ubuntu server IP(192.168.2.5). I hope this information is help full. let me know if you need more info. Thanks for your help.

As I asked above, how are you delineating between the two networks???. You are putting two subnets, with TWO DIFFERENT DEFAULT ROUTES, into your DHCP config. Not a problem, but the DHCP server is only going to give out what you TELL IT TO.

If you have one switch, and all your machines are configured into one domain, then they're going to pull the DHCP info accordingly. If you want ALL your machines to get the same default route, then change it in the dhcpd.conf. You've clearly got one set at 192.168.2.5, and another at 192.168.1.5.