guys i found this problem happen this morning my vlan3 hotspot dhcp network is 192.168.3.0/24 but the problem is some of mac user getting 192.168.1.1 i think this is from outside or someone plug a router in my network if i trace this show 6 hops, and if i ping its reachable. i have also 192.168.1.0/24 in my vlan1 but i disable to isolate the problem and i found out this another .1.1 dchp please how can i stop this guys?

C:\Documents and Settings\ChefAccountant>ping 192.168.1.1

Pinging 192.168.1.1 with 32 bytes of data:

Reply from 192.168.1.1: bytes=32 time=412ms TTL=251
Reply from 192.168.1.1: bytes=32 time=476ms TTL=251
Reply from 192.168.1.1: bytes=32 time=363ms TTL=251
Reply from 192.168.1.1: bytes=32 time=188ms TTL=251

C:\Documents and Settings\ChefAccountant>tracert 192.168.1.1

Tracing route to 192.168.1.1 over a maximum of 30 hops

1 <1 ms <1 ms <1 ms 192.168.3.1
2 143 ms 138 ms 61 ms 121.96.14.1.bti.net.ph [121.96.14.1]
3 151 ms * 201 ms gi5-2.ccore.rsv.bayan.net.ph [202.78.96.238]
4 141 ms 160 ms 42 ms gi5-2.ccore.rsv.bayan.net.ph [202.78.96.238]
5 * * * Request timed out.
6 77 ms 62 ms 55 ms 192.168.1.1

Create a new dhcp network and pool using a different scope then change the dhcp lease time to expire on the old pool. Someone has installed a router and they are plugged into the wrong port and sending out IPs from there location. Happens all the time.