SGE2010P - DHCP Relay - offer packet not reaching host

Cpattonsfs · ‎02-20-2015

I have an SGE2010P in L3 mode. I set up 2 vlans, 1 & 5. Vlan 1 has an interface of 10.0.3.252; Vlan 5 is at 10.0.10.9. I have defined the DHCP at 10.0.3.4 (on vlan 1) and enabled DHCP Interface for vlan 5. Put switch port g28 in access mode on vlan 5 and connected client machine. Set up wireshark on both DHCP a server and client. DHCP server is receiving the DHCP discovery packet with the correct relay agent address (10.0.10.9), and it sends back an offer packet to that address, but it is never received by the host machine. What am I missing?

Aleksandra Dargiel · ‎02-23-2015

Hello,

From your explanation looks all is configured as expected. It may be worth checking exactly what options DHCP offer contains. However please double check if all your settings are as follows:

http://sbkb.cisco.com/CiscoSB/ukp.aspx?vw=1&docid=1480df0d341148adaf83817994c0b328_Define_DHCP_Relay_on_Layer_3_on_the_SFE_SGE_Stackable_Manage.xml&pid=2&respid=0&snid=11&dispid=0&cpage=search

Regards,

Aleksandra

Cpattonsfs · ‎02-23-2015

Thanks. The only thing different in my configuration is that I have added VLAN 5 as a "DHCP interface." I don't really know exactly what that means, but from the user guide it looked like that would enable the relay for that vlan.

I'm wondering if it might be a routing issue. It looks like nothing in the routing table for the DHCP server would match except 0.0.0.0. Do you typically have to create static routes for DHCP relay?

Aleksandra Dargiel · ‎03-03-2015

Hello,

DHCP server typically is on subnet of one of the switch IP interface. Thus there si no need to indicate where the server is however you have to indicate from which VLAN DHCP requests are relayed. For example:

VLAN 1 - switch IP 192.168.1.25/24

DHCP server is on VLAN 1 with IP 192.168.1.1/24

Other VLANs:

VLAN 5 IP address 192.168.5.254/24

VLAN 10 IP address 192.168.10.254/24

enabling DHP relay from VLAN 5 and VLAN 10 is required.

Please check IF you have IP addresses on the switch of other VLANs 5 and 10

Regards,

Aleksandra

Cpattonsfs · ‎02-23-2015

So I'm probably going to sound like a total idiot, no matter the answer to this question, but I think I am missing something very fundamental about this process. Do I need a router on the local network to handle this? I assumed that the SGE2010 would handle the routing for inter-vlan communication, but perhaps I'm wrong.