Cisco 1841 basic config

[kengor007]

I'm in a bit over my head and could use some help. I need to set up a Cisco 1841 to give Internet Access to a LAN and provide DHCP addresses to clients and NAT. Here is what I have.

WAN IP - 69.125.57.189
DNS - 167.206.245.129

LAN - 10.5.1.1
Mask - 255.0.0.0

I have 10 clients that need to get IP addresses and access the Internet.

thanks,

Ken

 

[chieftan]

Configure your DHCP scope...... On the LAN side of things you will need to set this as the DHCP (Helper addresses).

Router(config)#ip dhcp pool <name>
Router(dhcp-config)#network <range / subnet mask>
Router(dhcp-config)#domain-name <your domain - mydomain.com>
Router(dhcp-config)#dns-server <your dns server address>
Router(dhcp-config)#default-router <normally the ip address of your lan interface> - basically the default gateway for the DHCP
Router(dhcp-config)#lease <the lease times you want for the addresses>

Then set up your access list for the NAT on the required interfaces as shown:-

Your ethernet interface will be the NAT inside:-

Router(config)# interface ethernet 0
Router(config-if )# ip address <your IP address>
Router(config-if)#ip nat inside

Router(config)# interface serial 0
Router(config-if )# ip address <your ip address WAN)
Router(config-if )# ip nat outside

Router(config)# ip nat pool overloadpool <wan address> prefix-length <Prefix length>
Router(config)# ip nat inside source list 1 pool overloadpool overload
Router(config)# access-list 1 permit 192.168.32.0 0.0.0.255

Hope this helps.....

 

[chieftan]

Apologies, did not read all your information correctly.

Are you utilising a whole class A address range for just 10 clients or are these 10 clients just part of that complete range?

 

[kengor007]

Thanks for the information, i'll try this later today. We are using the whole class A and have other host's on it that will have static Ip's. But we need to provide DHCP addrresses to about 10 PC clients.

thanks,

Ken

 

[chieftan]

If you are issuing out DHCP addresses within a given range and have staic IP's there then make sure you also use the dhcp excluded address command as well in global config mode. This will need to include all IP addresses that are static (might be a few with a class A range). If you dont exclude these addresses then the DHCP may well assign them dynamically and then you will have issues.

Remember with the ACL that it can only include these 10 address, so rather than a range it may be better to stipulate each dress seperately with a 32 bit mask.