Cicso 2611 router DHCP relay config 2

[Andreh]

G'day all,

I am currently looking to configure a Cisco 2611 with IOS 12.2 in a remote site as a DHCP relay agent. The network is Win2k Active Directory. I have been confused a bit as i was led to believe that i was working on a pix501 but after some searching around discovered this to be wrong. Our network WAN is configured using VPN's setup by a third party isp.

The local subnet the 2611 is in:
Subnet: 192.168.1.x

The DHCP server subnet and address is:
Subnet: 192.168.0.x
DHCP Server: 192.168.0.81

I beleive the "ip-helper" command is the one i am after. I also understand that some ports need to be closed.

Any configuration help appreciated.

AndreH.

 

[ecafracs]

here is the config ,configure it on the local interfcae connected to the local netowrk

interface Ethernet0
ip address 192.168.x.x 255.255.x.x
ip helper-address 192.168.0.81
no ip directed-broadcast

 

[Andreh]

Thanks for the quick reply ecafracs,

What does the "no ip direct-broadcast" command do?

Is that to disable the Netbois broadcasts?

andreh

 

[StarTAC]

u're right, u need to block some ports if u are using the IP helper address feature...

the ports are for UDP traffic that is also forwarded along with the UDP packets for DHCP, and include:

1. time service [37]
2. IEN-116 name service [42]
3. TACACS service [49]
4. DNS [53]
5. TFTP [69]
6. NetBIOS name server [137]
7. NetBIOS datagram server [138]

to prevent the forwarding of packets to these ports, use this command:

conf t
no ip forward-protocol <port/service>

this should allow u to relay DHCP on your router safely..

good luck..

 

[Andreh]

Great,

Thanks for both of your comments. I had a rough idea, but just looking for a confirmation

Cheers.