Please help!!!<br><br>I have 4 x Cat5500 switches all linked together.<br>I have an NT4 network with NT handling DHCP,WINS and so on.<br>All i need these switches to do is use the auto sensing 10/100mbps and nothing else.<br><br>Why the company have invested all this money for these switches is beyond me because we dont want to use any of the managable functions anyway apart from setting speeds.<br><br>I have set full duplex to ports for the servers but the rest is auto sensing.<br><br>I have various clients where dhcp is issuing the same ip address on the same network.<br><br>My first impression of this error was this is not possible usingDHCP,But Microsoft technet have said this is all to do with packets being sent across the network via the switches.<br><br>Has anyone seen this before if so can someone explain this to me in DUMMIE terms what i need to do to resolve this matter.<br><br>Thanks in advance<br><br>Offy<br>
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CAT5500 and DHCP Duplicate ip addresses
- Thread starter offy
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First off, tell me more about how the switches are connected together. <br><br>Is there a router involved?<br><br>Are there Win95 Clients involved? <br><br>Have you checked for duplicated MAC addresses?<br><br>Have you tried hard coding the port speed and duplex on the switch side? Computer side? Hard coding on both sides is really the best but I def. would not recommend having both sides autosensing(we have only seen problems with this).
Offy,<br>It sounds like the switches are not the only problem but you need to start basic. I would start by doing what bmorritt says and then look at a few other things like how long are your leases set for and make sure portfast is set up on any switches which ports connect directly to the switches that are not trunked. bmorritt is dead on though making sure at least one end is set up hard-coded because I have seen the same problems. Are the switches setup to run MultiLayer Switching (MLS)? If not they really cannot be causing the problems because they are a Layer 2 device that doesn't care about IP addresses (Layer 3 protocol). The only thing they can do is cause latency. Hope this helps. <br><br>Rob<br>P.S. Make sure people are not setting up static addresses in the range designated for DHCP. Happens all the time.
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The switches are all daisy chained together via module 1<br>The ip'sfor these switches are 10.202.127.1<br> 10.202.127.2<br> 10.202.127.3<br> 10.202.127.4<br><br>Module 1 on all the switches are 100 set full<br>Module 2 and 3 on all the switches are 10/100 auto-sense<br>Module 4 through to 9 on all the switches are 10 <br><br>This is a new building that has a 10mb connection via a router 10.202.127.253<br><br>No ip's are issued across the router the other building is all static ip's but are not in the range of the DHCP.<br><br>DHCP range is 10.202.124.1 to 10.202.126.254<br><br>Excluding ip's 10.202.124.255<br> 10.202.125.255<br> 10.202.126.255<br><br>The lease on the ip's is 4 days exactly.<br><br>The DHCP server is based here in the new office.<br><br>All serversuse the 10.202.127.x range so no conflicts of static ip's.<br><br>We have some Win95 machines on the network that after the lease runs out the machine does not re-issue new ip unless you do it manually through winipcfg.<br>Win98 issues new ip lease automatically no probs.<br><br>How can i check the switches to see if they are running Layer 2 not Layer 3?<br><br>Thanks for your response<br><br>Offy<br><br><br><br><br><br>
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I Have now found out that the network is only causing these problems now on win95 machines??????????<br><br>Does anyone know of the famous features(BUGS) in win95 that causes these duplicates and manual renew of the ip's after the lease has run out.<br><br>Thanks in advance<br><br>Offy<br>
Sounds like a problem I am still getting (cos I'm too busy to sort it out properly!):<br><br>I have a DHCP server running under NT. It works fine most of the time. Occasionally I have a printer running DHCP client pick up a new IP address that is different to the one it used to have. Unfortunately it does not register with the DHCP server as allocated and hence I get duplicate IP addresses.<br><br>Delete the mapping for the printer from DHCP, reboot the client and all is fine in the world.<br><br>Is there any similarity to your network? <p>Zel<br><a href=mailto:zel@zelandakh.co.uk>zel@zelandakh.co.uk</a><br><a href= > </a><br>
I have located some info off the Microsoft web site . I do not know if this is the cause , however it will not hurt to check .<br><br>Windows 95<br>Windows<br>The system has detected a conflict for IP address a.b.c.d with the system having hardware address 11:11:11:11:11:11. The interface has been disabled. <br><br>CAUSE<br>The Microsoft networking clients listed above do not respond to an address resolution protocol (ARP) request when the ARP sender's IP address is 0.0.0.0. This causes a problem with Dynamic Host Configuration Protocol (DHCP) environments, which may result in duplicate IP addresses on the network. <br><br>RESOLUTION<br>To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, please see the following article in the Microsoft Knowledge Base:<br><br><br>Q152734 How to Obtain the Latest Windows NT 4.0 Service Pack <br><A HREF=" TARGET="_new"> has confirmed this to be a problem in Windows NT 4.0 and Windows NT Server 4.0, Terminal Server Edition. This problem was first corrected in Windows NT 4.0 Service Pack 4.0 and Windows NT Server 4.0, Terminal Server Edition Service Pack 4.<br><br>Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available<br><br>MORE INFORMATION<br>Non-Microsoft DHCP clients fill in the sender's IP address with 0.0.0.0 when using ARP to check if the DHCP lease that it has been offered is a duplicate address on the network. Because the Microsoft clients above do not respond to this ARP, it is possible to end up with duplicate addresses on the network.<br><br>The following information is taken from RFC1541:<br><br>The client may issue an ARP request for the suggested request. When broadcasting an ARP request for the suggested address, the client must fill in its own hardware address as the sender's hardware address, and 0 as the sender's IP address, to avoid confusing ARP caches in other hosts on the same subnet. If the network address appears to be in use, the client sends a DHCPDECLINE message to the server and waits for another DHCPOFFER. As the client does not have a valid network address, the client must broadcast the DHCPDECLINE message. <br>
Offy, <br><br> I don't know of anything official on it but I have see a similar problem on our network. (Mostly win95 but a few win98 machines) The win95 clients don't always release their IP addresses when they run out. Win95 is setup to always attempt to get the same address it had before when the lease ran out. So when a machine is off for a few days(even a day or if it is a laptop that leaves periodicly) and the lease runs out and then someone else gets that IP address. The machine gets fired up again, tries to renew its old IP, can't but then keeps it anyway. We have several Vlans here and we have seen it most often on the network that is always changing. (well all our networks are constantly changing but one more than others) I don't know what else you can do but to send out a memo informing everyone that if they get that duplicate ip address message to try a release renew first and then call you if they still have problems.<br><br>Brian
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I, too, have seen this but since it was very infrequent I had not devoted much time to troubleshoot it. Being a school district, it is not uncommon to have Macs along side older PCs on the same network segment. I find that occasionally that I get reports of duplicate IP addresses between a Mac and Win95, both using DHCP. I thought that perhaps the Mac was not releasing the IP address, but from what I'm hearing here, it's probably the Win95 that's the problem!<br><br>So would having a shorter lease of 12 hours and having a policy of turning off all machines every night help? That is, if a Win95 machine is off and it's lease expires, when it is turned back on, would it be forced to get a new IP address?<br> <p>Steve Evans<br><a href=mailto:sevans@richmond.k12.va.us>sevans@richmond.k12.va.us</a><br><a href= Public Schools</a><br>>> Custom Web design for $45/hour&hosting<$10/mo-> theowl@theowl.com <<
It is supposed to be forced to get a new IP address...but the win95 machines don't always get their new one, they just 'deciede' to keep the old address. If I remember right it was if they were on and thier lease expired that you had better luck. Actually, the way our DHCP is set up the machines renew thier leases half way through. Ours are set up to lease an IP for 7 days but they talk with the DHCP server at 3.5 days about renewing thier lease. If the machine is off during the entire last half of that week, that is when we have problems because the server expires the lease and then gives it to someone else. Then that machine gets turned on again when the user comes back and win95 deciedes it wants to keep its old ip rather then get a new one.<br><br>I havent seen the problem in a few months but it does happen occasionally.<br><br><br>Brian
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