4800G: vlan routing with dhcp

[hasseily]

Hello,

I have a 4800G with 2 VLANs:

VLAN 1 is the default VLAN with ip 10.17.1.5/16

VLAN 2 is a single-port VLAN with a DHCP client IP.

I would like to route everything that isn't in 10.17.0.0 through that single-port VLAN. I've gotten it to the point where VLAN 2 got the DHCP info, the default route is through that vlan 2, and there's a direct route on vlan 1.

But the switch just doesn't want to move packets from vlan 1 through vlan 2, whatever I try. And I can't give vlan 2 a secondary IP from vlan 1 as it has a DHCP IP that seems to prohibit secondary IPs.

Any solution out there?

Thanks in advance,

Henri.

[jadielmota]

Dear Henri,

I am having some problems with a Microsoft AD/DHCP server and a switch 3com 4800g.

Did you resolve the problem you had? Since my problem is similar to yours, I would like

to ask you to share any idea you might have so that I can set up the infrastructure I need.

I attached an image of what I am trying to set up. Anything you can share would be helpful.

So, I have configured the IPs of the interfaces,

the default route and the relay on port 2. I have also set port 2 as trunk in order to have all traffic

from all other vlans go through it.

I am able to ping each individual interface with a host in the same network. Except the trunk interface (port 2).

I cannot reach any other interface but the one I am connected to and as a result I cannot get an IP address

from the AD.

Thanks in advance for anything you can share.

[manuel.bitzi]

Please post you configuraton of the switch, then we will help you.

br

Manuel

[jadielmota]

Dear Manuel,

Thank you for trying to help.

I have copied the switch's current config to a txt file.

I have changed type of the interface Gigabitethernet 1/0/2 to access and now from it I can reach the DHCP Server. When, it was configured as trunk I could not.

I have created a Subnet Scope in the AD like this:

Subnet B

Initial IP: 10.7.32.20

Final IP: 10.7.39.254

Mask: 255.255.248.0

In the Scope Options, I have added a router with the IP address of the DHCP relay, in this case 10.7.32.1.

Now, what I need to find out is how to make vlans 3 and 4 to communicate with vlan 2, for the hosts to receive their

IP addresses.

So, do you know how to make vlans 3 and 4 to communicate with vlan 2? Do you think there is anything wrong with the

configs I have made so far?

Please, let me know what you think.

[manuel.bitzi]

Hi

Looks like a lab config. :-)

some question/hints to help:

• 10.7.1.6 is your dhcp server and is on port 1/0/2?
• does the dhcp server have routs to vlan 3 and 4?
• do the dhcp scope have the default gw to 10.7.32.1 resp. 10.7.16.1?
• add dhcp relay to vlan 4
• Where is your client connected?
• Add static ip config to the client and check ip connectivity
• what does "disp dhcp relay server-group 1" show you?

br

Manuel

[jadielmota]

1. Yes, the IP address of the DHCP server is 10.7.1.6 and once I connect port 1/0/2 to the network I can ping the DHCP server from the console of the switch

2. I found a way to create a static route through the DHCP server. I am sending you a couple pictures showing you how I did it.

3. Yes, the scope 10.7.32.0/21 has the gw set up to 10.7.32.1 - I am trying to get this network to work first, If I can get it to work I will use the same technique for the 10.7.16.0/23 network

4. Once I can get the vlan 3 to work, yes I will add dhcp relay to it

5. My client is connected to vlan 3, with the static IP of 10.7.32.2

6. With the static IP I can only reach the interface 1/0/3 that has the 10.7.32.1 address, I cannot reach the others - route problem

7.Display dhcp relay server-group 1 shows me: No.1      Group IP 10.7.1.6

Please let me know what you think about the setup. I believe what I need to get the setup to work is a route between vlan 3 and vlan 2 in the switch. 

The default route is set to 10.7.1.20 which is the router in network 10.7.1.0, which the DHCP server belongs to. But, the two networks cannot communicate.

Thanks,

Jadiel