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Cisco Switch DHCP / Update Windows DNS

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7 replies

by lewko98

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Hello,
I have just a general question, and havent had any luck searching for the answer, any information or direction would be greatly appreciated, here are the details:
Right now DHCP on our network is handled by a Catalyst switch 4506, but the problem is it is not updating our DNS, like as in a windows Active Directory Integration Zone. The question is? Is there a way/commands to have the Cisco switch update our Windows DNS server when a DHCP clients lease is up, or is released?

Thanks for your time.

7 replies

by beentherebefore

If you have MS Active Directory running
You would need to have DNS running somewhere in your network.
I would check to see if the correct DNS servers are being offered by the switch.
Check to see if scavenging is turned on to get rid of old address
Try ipconfig /registerdns from a workstation and see if teh record updates properly in DNS

by lewko98

Good point beentherebefore, I dont believe scavenging is setup properly. The Cisco switch is handing out the correct DNS servers and hosts are registering themselves, just not deleting from DNS when they are removed from the network.
Im not sure how a Cisco switch DHCP, Updates DNS, the reason I ask is because only about a quarter of my A records have corresponding PTR records, Im inherting this position, and I figured this was due to DHCP being on a ciso switch and the switch not updatind the Windows DNS server with PTR records.
Basically my question is, if scavenging is setup correctly, will I be missing out on advantages (such as PTR record creations per A record and Dynamically updated DNS, and if/ whatever else) if I leave DHCP on a cisco switch as opposed to moving it to a Windows server?

Thanks.

by cg it

Personal opinion is you shouldn't have revolving door hosts on the network.

hosts are either authorized therefore have a computer account on the domain and they register themselves in DNS or they don't and shouldn't be allowed on the network let alone register themselves in DNS.

by beentherebefore

Log on to the Server.
Go to Admin tools DNS
Right click on your DNS zone and select properties.
Click on the advanced tab, make sure the check mark for enable scavaging for stale records is checked and you have a set number of days.
I use a time of 4 days to keep up with laptops that move around to different subnets. If you have equipment that doesn't change much you can leave the settings at the MS default

by lewko98

CG IT,
I understand what you mean, we have only authorized hosts, but over times, we re-purposed machines and there IP and DNS is left to be cleaned up manually (due to improper scavenging settings like pointed out a bit earlier by beentherebefore).
The question is more based towards a Cisco switch DHCP and a Windows DNS server VS a windows DHCP and DNS server.
If DHCP is left on the Cisco switch will advantages be missed such as PTR records being created for A records, and dynamic updates. Or is this something that can be done from the Cisco switch, or is it worth it, etc?

by cg it

the capabilities of the DHCP server might be different between devices. Consumer level router DHCP doesn't have options that are configurable.

If you don't mind 2 points of administration, there's no need to change where the service is hosted.

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