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SG300-52 is apparently using DHCP against my wishes

Hello there,

(see attached image)

Each modem has 7 IPs assigned by the ISP, and uses DHCP to deliver them. The thing is, 6 out of each 7 router interfaces get their IPs correctly, but the seventh one never gets a lease. I checked with the ISP and the missing 3 are all assigned to the SG300 MAC, which leads me to believe that in each VLAN, the switch must be using DHCP to get its IP. Why is this happening? The switch is set to layer 2, so I can't set each interface to use Static IPs.

Note: I'm not a network management expert, nor do I know why everything is set the way it is (it was like this before I took charge of it, recently found out this little detail while monitoring traffic).

Any help is appreciated, thank you very much.

Everyone's tags (1)
Cisco Employee

Hi AdaptiveGroup,SG300 by

Hi AdaptiveGroup,

SG300 by default is in layer 2 and has one IP interface which is set to DHCP client in the default VLAN 1.

That would mean that you might loose one (but only one) IP address from your DHCP pool given by ISP. This can be quite easily overcome by setting up static IP on the switch, which in theory can be even from different pool.

Otherwise, perhaps modem interface needs one IP address as well...

You might need to take a look on the switch configuration and the easiest way is console connection. Please contact our Small Business Support center for assistance, they would be glad to assist you with it:







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