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CISCO SWITCHES FOR SMALL and MEDIUM BUSINESS

Introducing the next generation of Cisco Small and Medium Business Switches. Cisco is refreshing its SMB Switch portfolio. Click here  to learn more.


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stephane.basse
Beginner

DHCP relay with SF 302-08P

Hello all,

I try to configure a DHCP relay with a Cisco SF 302-08P. I configure correctly the différente option ( Server DHCP, VLAN, Gateway ...). When a pc send a dhcp request, the request arrive on the server. And the server send the reponse to the switch. But the response doesn't arrived to the pc. It's seems to blocke by the switch.

The configuration is :

serveur dhcp (IP@ : 10.10.0.253) ----> router ( 10.10.0.254, 10.30.0.1 ) ----> switch ( 10.30.0.3 ) ----> PC

Can you help me ?

Thank you

Stéphane

4 REPLIES 4
Tarquin Joseph
Beginner

Hi Stephanie,

From the manual for these switches I saw this:

DHCP Relay Limitations

In Layer 2 mode, the switch inserts its own DHCP option 82 with ingress VLAN and ingress port information in the DHCP message it receives from the DHCP clients. Because of this, the DHCP servers must support DHCP option 82. The switch discards DHCP messages with option 82 that it receives from the DHCP clients.

In Layer 3 mode, the feature can only be enabled on the IPv4 interfaces.

Can you verify that the DHCP server is configured to support DHCP option 82?

Regards,

T.

I'm having a similar problem with the Cisco SGE2000 and Server 2008 R2 DHCP server.

Do you know how to configure option 82 on windows? I know it is supported but not in the default option lists.

Sorry Andrew.

Wish I could assist with that.  There is an article under Microsoft tech blogs that deals with that.  Do a search on "Option 82 DHCP" and you should get some useful results.

Regards,

T.

Hello Joseph. I have the same problems as Stephane with my switch SG300-10P. My dhcp server supports option 82 and send DHCP OFFER packet to client PC. I`ve traced this answer with wireshark and port mirroring. DHCP OFFER packet comes back to SG300-10P but don`t send to client port.

Problem was resolved with upgrading firmware to the latest version