SGE2000 DHCP Relay Issue

[kanephil1]

I am looking for some help with DHCP Relay on a SGE2000 switch.

I have configured two VLANs on the switch, VLAN2 (192.168.10.x/24) and VLAN3 (192.168.9.x/24). I have the switch in Layer 3 mode. I have configured the DHCP relay server of 192.168.10.4 and the DHCP Interfaces as VLAN3. All of the IP Static Routes were generated by the switch.

If I put a client computer on a port that is Untagged VLAN 3 and try to get a DHCP address from the server on an Untagged VLAN 2 port I never get a response back.

I have done some packet captures and here is what I have found:

1. I see the DHCP broadcast on the client computer
   
2. I see the DHCP Request on the DHCP server coming from the IP assiged to the switch on VLAN 3 (192.168.9.254)
   
3. I see the DHCP server respond with a DHCP Offer
   
4. The DHCP offer never gets to the client computer
   

I can't seem to get a DHCP address to any system not on the same VLAN as the DHCP server. Option 82 is disable and I did try enabling it, which made no difference.

Any help would be great.

Thanks,

Phil

[David Hornstein · Accepted solution]

Hi phil,

Have you created a static route on the DHCP server that points back to the 192.168.9.0/24 network.

The gateway for that network,  from the DHCP relay servers perspective,  is the VLAN2 IP address of the SGE2000 switch.

i would think that if you tried to ping the VLAN3 switch  IP address from the DHCP server now,  you will not get a reply.

When you create a static or persistant route in the DHCP server,   you then should be able to ping VLAN3 IP address of the switch.

regards Dave

[kanephil1]

Dave,

Thanks for the response.  After reading your post I tried to ping the switch on the 192.168.9.0/24 network and could not get there.  Once I switched my default gateway on my DHCP server to the switch IP on the same VLAN everything worked.  I can now get DHCP address on VLAN 3.

Thanks,

Phil