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TOPIC: Issue with Cisco L3 switch with multiple DHCP scopes.

Issue with Cisco L3 switch with multiple DHCP scopes. 7 years 7 months ago #29313

  • skepticals
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VLAN 1
DHCP Scope 10.15.2.0

VLAN 8
DHCP Scope 10.15.8.0

All the ports on the switch are in VLAN1, but I am getting some PCs getting an IP from VLAN 8. How is this possible?

I did notice that the VLAN interface does not have an IP assigned to it, would this cause an issue?

I thought that a PC would have to be in the same VLAN because DHCP is based on broadcasts.

What could cause this?
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Re: Issue with Cisco L3 switch with multiple DHCP scopes. 7 years 7 months ago #29347

  • Smurf
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No one has problably replied because what you are describing shouldn't be happening. You are correct, if the switch port is in a particular VLAN then it will be sgemented at layer 2 from all other VLAN ports.

Hmm, can you do a packet capture ?

I would also double check the VLAN configuration.
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Re: Issue with Cisco L3 switch with multiple DHCP scopes. 7 years 7 months ago #29357

  • S0lo
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I'd first double check the VLAN config as Smurf suggested.

What DHCP server(s) are you using? is it a router or a Win/linux box?. If the later, then make sure the DHCP server for VLAN8 is connected to a VLAN8 port on the switch. If your using a router as your DHCP server (i.e router on a stick for both VLANs), then I'd double check the masks set for the two scopes/pools (apparently /24 in your case).

Still no hope? Then what happens when you set one of those ports to VLAN8, does the PC connected get a VLAN8 IP or a VLAN1 IP?
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Re: Issue with Cisco L3 switch with multiple DHCP scopes. 7 years 7 months ago #29367

  • skepticals
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Sorry, I didn't make myself clear. The DHCP is given from the Cisco switch itself.
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Re: Issue with Cisco L3 switch with multiple DHCP scopes. 7 years 7 months ago #29373

  • S0lo
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Never mind, A post of your config could help.
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