Need help: configuring DHCP relay agent

[kayjoon]

We'll use 2 subnets on Cat3550 switch.

(192.168.1.0/24 and 192.168.2.0/24)

The switch has 2 VLANs and each VLANs have 12 physical ports.

I'd like use DHCP relay on each VLAN.

for example,

service dhcp

interface fa0/1

swichport

switch mode access

switch access vlan 10

interface fa0/2

swichport

switch mode access

switch access vlan 20

interface vlan 10

ip address 192.168.1.1 255.255.255.0

ip helper-address 10.1.1.1

interface vlan 20

ip address 192.168.2.2 255.255.255.0

ip helper-address 10.2.2.2

Is this possible to use?

Does someone have reference configuration?

Thanks in advance, :)

quantumn@empal.com

[amit-singh]

Hi,

Yes, you can configure 3550 switch to act as the DHCP relay agent. The command Ip helper-address doesnot enables the relay feature on 3550 rather it forwards the DHCP braodcast request by the client on a segment as a unicast request to the server located on a differnt subnet.

Please see the link below and will come handy:

http://www.cisco.com/univercd/cc/td/doc/product/lan/c3550/12225seb/scg/swdhcp82.htm#wp1099627

HTH,

-amit singh

[Richard Burts]

I am not clear from this post whether you intend to configure DHCP on the 3550 or on some external device? Thel helper address you configure points to the router IP address which suggests that the router might be offering the DHCP service.

If the router is offering the DHCP service then you do not need to configure the helper-address. The DHCP request is a local broadcast which the router will hear and will respond to without needing the helper-address. If the router is not offering the DHCP service then you do need the helper address and the address specified in the helper-address needs to be the IP address of the remote device which does offer DHCP.

HTH

Rick