DHCP Help!

[Mark182]

FYI attachment...

 

Anything that gets a DHCP/BOOTP won't get an IP address.

 

Have tried to reconcile scopes they keep coming back....

 

Everything that re news does not get an IP address...

[Steve21]

I'm assuming the 1s are just the fact you cut off part of the end? As per the scope. If so what do you mean as it's showing IPs assigned :s

 

Steve

[Mark182]

We have 11 scopes in total but only two ranges are pushing out TYPE = DHCP/BOOTP, all other scopes are fine and renewing leases. Two of them don't seem to be. As the lease runs out on a device it then won't get an IP address.

[Davit2005]

Anything being changed on switching i.e. layer 3 ip address helpers?

Compared to the vlans on the switches does anything look different?

Are you using any routers or firewalls to relay DHCP requests to the DHCP servers?

[Mark182]

No, no changes on switches or anything.

[Mark182]

Anyone ever seen this "An error occurred while renewing interface local area connection: The name specified in the network control block is in use on a remote adaptor. The NCB is the data. "

 

We have rebuilt DCHP on our DC and turned off fail over, All windows updates installed. Really struggling with this.

 

Seems when a device is restarted even though it has a valid lease before restart it then won't use that address after a restart.

[Mark182]

A little update, used our shutdown to make sure everything was turned off last. Came in early and started to turn computer rooms on.....From the first post the dodgy MAC address is requesting all our IP address and filling up the scopes so no one can log in. I checked on the DHCP server last night when everything was off and all looked okay.

 

I think it's wireshark time to see what continually makes DHCP requests to take up all the addresses.

[Mark182]

Just a little more information see attached picture. This IP 10.75.59.254 address is constantly requesting addresses. The 10.75.59.00 scope is our wireless (SID not broadcast) we stop dishing out addresses at .50

 

Whatever is it keeps exhausting our .54 and .55 scopes until there is no more left to dish out.

 

If you that the IP address into IE it comes up with a page about the website’s security certificate and then you click continue the page cannot be displayed.

 

When all devices are off at night time we don’t have to reconcile our scope but as soon as users come in and power on desktops ect then everything goes nuts.

 

We have spanning tree enabled on switches and they are not maxing out any of them. It’s only happening on our .45 .55 range.

 

We’ve tried shutdown commands on that IP address no joy

[Duke5A]

You typically see those goofy unique IDs due to Remote Access Services. Are you running RAS on anything?

 

You can also try going into the scope properties and under the advanced tab at the top hit the radio button to only assign addresses to DHCP clients.

[Mark182]

Funny you should say that, We have RDS set up on last (Friday 27th) Our ISP made some changes....

 

Yeah only DHCP is selected.

 

Thanks for the reply!

[Mark182]

I came in on Saturday to do some testing. I logged in remotely to our DC checked "reconcile" was all fine. I then logged onto the server once on site and checked again, all fine. I turned one random computer on one pops up in the reconcile box. I turn off that desktop and unplug from the network and reconcile, leave it 20 minutes check again all clear. Turn another random desktop same again. I go through the process a few times and same outcome.

 

I have checked all our servers the RRAS role is not installed on any of them.

 

 

It seems when a desktop boots up and checks it current lease that's when errors occur. We have rebuilt DHCP on this server from scratch so I am really confused!

 

This "MAC" addresses all start "31302e37352e353522313XXX

 

Anyone any ideas?

[Mark182]

We think its switch related. FYI attachment, I can a port in a VLAN lets say .54 but if you release and renew IP then it'll grab a .55 even though it should not. Going to do some more testing tomorrow, as we are only having issues with .55 and .54 scopes.

[Steve21]

You sure on that last bit? All your other scopes are /23 with 2 ranges of IPs within it from your screenshots above etc

 

Steve

[Davit2005]

Can you post a running config of switch??

[ITGURU]

Do you have multiple DHCP servers for redundancy? None of them issuing IP Addresses?

 

I've had an issue before with a DHCP server deciding not to issue any IP addresses at end of lease, but luckily I had 2 and the second one was taking the load whilst I rebooted the first one then both restored serving addresses.

[Mark182]

Do you have multiple DHCP servers for redundancy? None of them issuing IP Addresses?

 

I've had an issue before with a DHCP server deciding not to issue any IP addresses at end of lease, but luckily I had 2 and the second one was taking the load whilst I rebooted the first one then both restored serving addresses.

 

We did have "failover" set up on another DC but turned it off as there was errors

 

- - - Updated - - -

 

Can you post a running config of switch??

 

Will do when back in tomorrow

[Mark182]

Issue resolved!!

 

We unplugged all the fibres so only server room and surrounding rooms were connected. Then we plugged each fibre in one by one until the issue came back. Went to that hub room and unplugged all switches and plugged them in one by one until the issue came back. Logged onto the switch and “native vlan mismatch” found the port and traced it back and BAM! A loopback in a classroom…we have STP enabled so not really sure how it did not shutdown the port. It was in the smaller school attached to ours! Do’h!