wrong DHCP address

Alvaro Rugama · ‎03-13-2014

Hi everyone

I'm having this issue with my network.

We have like 20 vlans on a network. We had DHCP relay configuration with all the vlans, all was working ok, but somehow today, one of the vlan is not receiving the proper addresses from the DHCP Server.

We have two SW-3850 in a stack as a Core, where we had this configuration:

interface Vlan1
ip address 10.2.0.11 255.255.0.0
!

Interface Vlan30

ip address 10.100.30.1 255.255.255.0
ip helper-address 10.2.173.151
!
interface Vlan32
ip address 10.100.32.1 255.255.255.0
ip helper-address 10.2.173.151
!
interface Vlan34
ip address 10.100.34.1 255.255.255.0
ip helper-address 10.2.173.151
!
interface Vlan36
ip address 10.100.36.1 255.255.255.0
ip helper-address 10.2.173.151

each vlan has it proper DHCP scope configure on the Server; the Server is on VLAN1 as you can see.

Don't know why when I connect a client into an access port on the same switch on VLAN34 we receive an address from 10.2.0.0/26, more weird is that that client can navigate to other networks without being on a VLAN1 port.

This happens on wire and wireless devices on VLAN34 only, other VLANs are working ok.

Hope you can help us with this.

Best Regards

Alvaro Rugama Cerda

Alvaro Rugama · ‎03-13-2014

this is the output of the debug ip dhcp server events and server packet

*Mar 13 12:22:42.268: DHCPD: Finding a relay for client 015c.260a.4e0f.42 on interface Vlan34.
*Mar 13 12:22:42.268: DHCPD: there is no pool for 10.100.34.1.
*Mar 13 12:22:42.268: DHCPD: Looking up binding using address 10.100.34.1
*Mar 13 12:22:42.268: DHCPD: setting giaddr to 10.100.34.1.
*Mar 13 12:22:42.268: DHCPD: BOOTREQUEST from 015c.260a.4e0f.42 forwarded to 10.2.173.151.
*Mar 13 12:22:42.268: DHCPD: Reload workspace interface Vlan1 tableid 0.
*Mar 13 12:22:42.268: DHCPD: tableid for 10.2.0.11 on Vlan1 is 0
*Mar 13 12:22:42.268: DHCPD: client's VPN is .
*Mar 13 12:22:42.268: DHCPD: Finding a relay for client 015c.260a.4e0f.42 on interface Vlan1.
*Mar 13 12:22:42.269: DHCPD: there is no pool for 10.2.0.11.
*Mar 13 12:22:42.270: DHCPD: Reload workspace interface Vlan1 tableid 0.
*Mar 13 12:22:42.270: DHCPD: tableid for 10.2.0.11 on Vlan1 is 0
*Mar 13 12:22:42.270: DHCPD: client's VPN is .
*Mar 13 12:22:42.270: DHCPD: forwarding BOOTREPLY to client 5c26.0a4e.0f42.
*Mar 13 12:22:42.270: DHCPD: Forwarding reply on numbered intf
*Mar 13 12:22:42.270: DHCPD: no option 125
*Mar 13 12:22:42.270: DHCPD: broadcasting BOOTREPLY to client 5c26.0a4e.0f42.

What I see is that the mac address is seing from VLAN34 and VLAN1, but why?

Best Regards

Alvaro Rugama Cerda