VOIP and DATA vlan configuration Using Microsoft DHCP server.

[nikhilaluvila]

Dear Experts,

Please help me out from this situation and i am just stepping into cisco.

In my organization we have Polycom phones and a cisco SG300 series switch.I want to configure the way like this the system should have to connect to IP phone and from IP phone the connection goes to the switch ports, which means voice and data on same port.I created vlan and assigned the ports also to the vlan.I am using Microsoft DHCP server which i created two scopes for the voice and data vlan.10.120.1.0 for data and 10.120.1.100.0 for voip.how should the IP phone get 10.120.1.100.0 series IP and data will get 10.120.1.0 series IP.Please help me for this and give a solution.

[mahmoodmkl]

HI, Where do u plan to configure u r intervlan routing.

On the switch which is going to do the intervlan routing and under the SVI of the voice vlan configure the ip helper-address command like below.

ip helper-address (IP Address of DHCP Server)

Thanks

[nikhilaluvila]

Dear mahmoodmkl

On the same switch i am going to do inter vlan routing,but the on switch sg300 the command that you mentioned is not there.So any other method is there.

Thanks for your prompt reply.

[Shankar Murali]

Step 1. Log in to the web configuration utility and choose IP Configuration > DHCP > Properties. The Properties page opens
Step 2. (Optional) Check Enable in the Option 82 field to enable option 82 for DHCP packets. Option 82 is used to protect the switch from attacks such as IP and MAC address spoofing. Option 82 provides information about the location of the DHCP client through the insertion of the circuit ID (interface name at which the DHCP client is connected and the VLAN name that corresponds to the interface) and the remote ID (MAC address of the switch) in the packet header of the DHCP packet. The DHCP server then uses this information to assign an IP address.

Step 3. Check Enable in the DHCP Relay field to globally enable DHCP relay on the switch.

Step 4. Click Save. DHCP Relay is configured on the switch.

Step 5. Click Add to establish a path from the switch to the DHCP server. The Add DHCP Server window appears.
Step 6. Enter the IP address of the DHCP server in the DHCP Server IP Address field.

Step 7. Click Apply. The DHCP server is configured to use the DHCP Relay Server Table.

Please refer to the below document of relay via interface configuration.

http://sbkb.cisco.com/CiscoSB/GetArticle.aspx?docid=d8d34abcd43d445f95073301cae9fbd2_DHCP_Relay_Configuration_on_Cisco_300_Managed_Switch.xml&pid=2&converted=0

[nikhilaluvila]

Thanks Murali.

Can i ask you one doubt.why we act the switch as dhcp relay agent.

[Shankar Murali · Accepted solution]

Since in our senario we have multiple broadcast domains (vlans ) we can not place dhcp server in each vlan. DHCP client will actually broadcast for dhcp discovery, this request will be captured by relay agent and forward to dhcp server as unicast. If relay agent (cisco term - IP helper) is not configured in switch , the dhcp discovery will be broadcasted with in the VLAN and the client will not get any response - because DHCP server is in a diffrent vlan.

-Shankar

[nikhilaluvila]

Thanks Murali......

I got an idea regarding that.