Dhcp server on 4507 without intervlan routing

[herve.sauton]

Hello,

I have a switch 4507 configured in level 2. It transports only the vlans. For needs for security the inter-vlan routing is made by a firewall. It is possible to configure the 4507 in server Dhcp for only one vlan without routing inter-vlan on it?

Regards,

[ankurbhasin]

Hi Friend,

If you are configuring 4507 itself as a DHCP server and the machines are directly connected to 4507 on some particular vlan and that vlan has a logical interface (layer 3 interface) configured for that vlan then yes it is possible as machines will get an ip address from DHCP server conigured on 4507 directly.

But incase the gateway is your firewall for that vlan then you need to configure your firewall in such a way then it fwd the DHCP request to the 4507 for that vlan.

HTH

Ankur

[devang_etcom]

hi Ankur,,,

first of all congratulation to be on TOP in NETPRO...

now when we are talking about DHCP services...when client boot up then it will search for the DHCP server...if switch it self as DHCP server then it will reply to client with the IP address and some configuration...right...so why is there issue regarding logical interface(layer -3)...

and also clear the issue regarding to firewall ...

regards

Devang

[ankurbhasin]

Hi Devang,

Thanks for your compliment.

When you configure a switch as a DHCP server you configure DHCP pool for some particular subnet right.

Now lets take as an example one DHCP pool configured but 2 machines connected to different VLANs.

Both the machines boot up and send the broadcast in their VLANS but DHCP pool is configured for only one subnet which will result in both machines in different VLANS getting same ip address which will be a wrong behavior.

Now what happen when you configure layer 3 interfaces for vlans. When the machines boot up and send a broadcast for DHCP it will also hit the logical interface and then the logical interface subnet is compared to the DHCP pool range and if the logical interface subnet lies in the DHCP POOL range machines for that vlan are alloted an ip address or else there is no way when the DHCP pools can be compared with the DHCP request from particular vlans.

I hope I am able to explain.

Regards,

Ankur

[devang_etcom]

hi ankur,,,

so as per DHCP behaviour ...DHCP server assing IP addresses as per the GID's(Gateway ID) major octat...right...so if i want to configure DHCP for multiple VLAN then i have to configure multiple layer 3 interface which are the gateways for appropriate VLAN...and i have to confiuger that number of DHCP pool right...

am i right with my funda...

regards

Devang

[ankurbhasin]

Hi Devang,

You are perfectly right.

Ankur

[herve.sauton]

Ankur and Devang,thanks for your response.

Regards,

[devang_etcom]

ya ,,,

u r always well come...netpro is good to resolve issues as wellas fundamentals...

regards

Devang