SG300-28 VLAN DHCP

[Info4uSrl]

Hi,

the scenario is quite simple….:

a customer of mine have a sg300-28 L2 switch where I have create a VLAN -ID 100- (is the first added VLAN) and I have assigned some ports as UNTAGGED on this VLAN. On VLAN 100 is provided a DHCP service from external server (let's assume IP from 192.168.10.100 to 192.168.10.200) and another external server provides IP addresses for the default VLAN 1 (let's assume from IP 192.168.222.150 to 192.168.222.240)

ISSUE:

On the default VLAN 1, all clients are able to obtain their IP address from the DHCP server (192.168.222.15x), but all clients on the VLAN 100 are NOT able to find any DHCP server and then to get a valid IP (APIPA is assigned by default).

I have read and searched on the community, but I was not able to find a solution.

I tried to change the port setting on ACCESS mode, TRUNK, etc. (I tried all possibility) but no one choise changed the issue.

In other words, the DHCP service seems to be not passed through on VLANs

The switch is running an old firmware  (1.1.1.8) and boot version but, reading posts, I have seen that also newer version are affected. I plan to update the boot and firmware versions, but I have to solve out this issue as first urgently

Many thanks in advance for any help and suggestion. Do not esistate to ask me more information

If possible, I'd like to use the WEB Interface instead of the console/command interface, since the customer "wants to know".....  :-(

[Seb Rupik]

Hi there,

Sounds like you need to configure an IP helper address on the SG300. I believe the config is:

!
ip dhcp relay enable
ip dhcp relay address <DHCP_SERVER_IP>
!

...if you have done this already, please attach your entire running config for the SG300 so we can take a better look.

cheers,

Seb.

[Seb Rupik · Accepted solution]

Here are the GUI steps:
https://sbkb.cisco.com/CiscoSB/GetArticle.aspx?docid=d8d34abcd43d445f95073301cae9fbd2_DHCP_Relay_Configuration_on_Cisco_300_Managed_Switch.xml&pid=2&converted=0

[Info4uSrl]

Many thanks Seb.

I solved upgrading the firmware (and also the boot image, but I don't think the new boot image changed anything in the problem solving) from my old version to the version 1.3.5.18, because some choises shown in the document linked there weren't in my GUI; after the firmware upgrading, I could set all parameters as suggested and it started to work corretly.

Now it works; I have still just to try if using a trunk port with DHCP set on standard VLAN1 as UNTAGGED and a DHCP set on VLAN100 as TAGGED it still works, but I think so, it should work.

Many many thanks to all for the answer and the great support

[Info4uSrl]

Thanks Seb.

[Daniele Giordano]

What is the IP address of DHCP server? Is DHCP server connected directly to VLAN 100?

If nom you must configure the "ip helper address" command.

Let us know.

Regards.

[Info4uSrl]

Dear Daniele,

thanks for your suggestion (I solved, see below); checking for your suggestion, I was not able to find any "ip helper address" command on console help.....

But I have found a lot of other post suggesting the same setting...... where is the "ip helper address" command? In enabled shell? In my version it is not present.

Many thanks again.

Giorgio