RE: DHCP NACK problems [7:44671]
Is it always NACKing for the same IP lease? Normally, the DHCP process works like this: The client sends a DHCPDISCOVER to find a DHCP server, the server responds with a DHCPOFFER, offering the client an IP, the client responds with a DHCPREQUEST to choose the IP address (in case it gets an offer for more than 1), and the server responds with a DHCPACK, sealing the deal. However, MS DHCP servers have a feature that allows them to detect IP address conflicts before responding with an ACK. What I would check is a few things: First, if this is happening due to a conflict detection, you should see under active leases in DHCP a BAD ADDRESS listed by the IP. If you see that, ping the IP in question. If you get a response, track down the PC, and do an ipconfig to find it's DHCP server. Then track down that server and kill it :) Hope this helps, Brian Hill CCNP, CCDP, MCSE 2000 (Charter Member),MCSE+I (NT4.0), MCSA (Charter Member), MCP+I, MCP(21), Inet+, Net+, A+ Lead Technology Architect, TechTrain Author: Cisco, The Complete Reference http://www.alfageek.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=44699t=44671 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: DHCP NACK problems [7:44671]
Also, to add to this... if you have a WINS server with a corrupt database, that could be adding to the confusion for Duplicate IPs. I've had this happen to me before, and didn't realize it until I decided to just look at the WINS server to see what it thought was true of the LAN topology. It's just something to keep in mind. Mark -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Brian Hill Sent: Wednesday, May 22, 2002 6:01 AM To: [EMAIL PROTECTED] Subject: RE: DHCP NACK problems [7:44671] Is it always NACKing for the same IP lease? Normally, the DHCP process works like this: The client sends a DHCPDISCOVER to find a DHCP server, the server responds with a DHCPOFFER, offering the client an IP, the client responds with a DHCPREQUEST to choose the IP address (in case it gets an offer for more than 1), and the server responds with a DHCPACK, sealing the deal. However, MS DHCP servers have a feature that allows them to detect IP address conflicts before responding with an ACK. What I would check is a few things: First, if this is happening due to a conflict detection, you should see under active leases in DHCP a BAD ADDRESS listed by the IP. If you see that, ping the IP in question. If you get a response, track down the PC, and do an ipconfig to find it's DHCP server. Then track down that server and kill it :) Hope this helps, Brian Hill CCNP, CCDP, MCSE 2000 (Charter Member),MCSE+I (NT4.0), MCSA (Charter Member), MCP+I, MCP(21), Inet+, Net+, A+ Lead Technology Architect, TechTrain Author: Cisco, The Complete Reference http://www.alfageek.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=44717t=44671 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
DHCP NACK problems [7:44671]
This may or may not be a Cisco issue but I am running DHCP on a NT 4.0 server and it's been giving Nacks for the past 5 days and is causing a major headache. Every Nack has been coming from the same subnet as the DHCP server which seems even more strange. I've watched the packets being broadcasted with a sniffer and I can see the client requesting, the server replying with all the DHCP information, the client request again, and the server then giving a nack. If I get an IP from a VLAN or token ring subnet, I don't have any problems. I've been trying to find a rogue DHCP server but there doesn't seem to be one. I don't think it's any of the routers because they don't need to cross them to get to the DHCP server (except VLAN and token ring which don't seem to have problems). Has anyone had similar problems and if so, did you come across a solution? We're starting to think the DHCP database might be corrupted and ready to blow it away (ack!) Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=44671t=44671 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
