DHCP and VLAN Routing on 4900

[btsoom]

I'm trying to setup a 4924 switch with two VLANs (default and VLAN4). Both VLANs are on separate subnets. I'd like the workstations on VLAN4 to receive DHCP from a router connected the default VLAN.



In the discussions here and in the 3Com Knowledgebase, it's been recommended that:



1. RIP be turned on

2. Both VLAN IPs be set to PRIMARY

3. UDP helper be enabled

4. Port 1 be a tagged port in both VLANs



I've done this and workstations on VLAN4 still cannot get DHCP from the router on the default VLAN. When the workstations (and router) are connected on the default VLAN (except port 1) DHCP works fine. When the upstream router is connected on port 1, DHCP does not work when the workstations are in either VLAN.



Has anyone setup a 4900 switch to route DHCP across VLANs?

[aydinkocak]

Hello;

Could you please check dhcp server connectivity to

VLAN mainly could you ping VLAN 1 and VLAN 4 Interface

on the 3COM 4900 on DHCP Server(Router).

Also you don't need and dynamic routing and

I thing Port 1 musy be untag to VLAN 1 and Tag to VLAN 4.

AYDIN KOCAK,

3COM Enterprise LAN Expert ( Pre & Post Sales),

TippingPoint Security Engineer,

CCNA,CCDA, CCIE R&S Written

[btsoom]

Aydin,



Thank you for your response. Here are my results:



1. I successfully pinged the DHCP server when the router & workstation are both connected to the default VLAN.



2. Ping was unsuccessful with the router on the default VLAN and the workstation on VLAN4. Since the workstation couldn't receive DHCP, I'd expect this to fail. So I repeated the test with the workstation IP set to an unused address in the router subnet and that also failed.



I also changed port 1 to untagged on default VLAN and tagged on VLAN4 and repeated the ping test with the same results.



I also verified that RIP is on, both VLANs are PRIMARY and UDP helper is on (with default ports pointing to the router).



FYI, the 4924 reports:

HW version is 0

SW version is 4.22

Boot Version is 1.01



This switch is a "basic" switch with no module installed.



Any help would be appreciated.







btsoom

[aydinkocak]

Hello;

I don't understand your topology please send en e-mail

your topology(visio or any format) to me : akocak@turkom.com.tr



Best Regards

AYDIN KOCAK,

3COM Enterprise LAN Expert ( Pre & Post Sales),

TippingPoint Security Engineer,

CCNA,CCDA, CCIE R&S Written