jamesmay Posted April 9, 2014 Posted April 9, 2014 Wondering if anyone can help... I have recently upgrade our DC to some new 2012R2 VMs on hyper v and have migrated the roles and services across. Our clients are now getting all the right details from the DHCP server (Router for their VLAN, DNS servers etc) but aren't able to connect to the DNS servers thus not get logon servers or access the internet. The VLANs are configured with an IP and also with a helper ip address to get to the dhcp. They can ping external IP address, but not the DNS server. If you put in google's public fns, you can access the internet. Any one have any thoughts?
synaesthesia Posted April 9, 2014 Posted April 9, 2014 am I right in assuming the DNS servers are not the DHCP servers then?
synaesthesia Posted April 9, 2014 Posted April 9, 2014 Ok - start simple, have you checked firewall? Even in place upgrade re-enabled the firewall when we moved up to 2012 R2.
jamesmay Posted April 9, 2014 Author Posted April 9, 2014 nothing that simple I'm afraid Firewall off on the DCs and the hyper hosts
synaesthesia Posted April 9, 2014 Posted April 9, 2014 what networking gear are you using, so we can get an idea of the vlan and routing setup?
jamesmay Posted April 9, 2014 Author Posted April 9, 2014 Force10 Core switch (3 Switches stacked) VLAN Config looks like this : interface Vlan 10 name Retouch_VLAN_10 ip address 10.101.10.1/24 tagged GigabitEthernet 1/0,2 tagged GigabitEthernet 2/1 untagged GigabitEthernet 2/37-43 ip directed-broadcast ip helper-address 10.101.60.11 no shutdown It all worked ok before we moved over!
synaesthesia Posted April 9, 2014 Posted April 9, 2014 Seems odd, one can only assume that it's software level. The network drivers in the upgraded OS haven't managed to detect and set VLAN accordingly have they?
jamesmay Posted April 9, 2014 Author Posted April 9, 2014 they were actually new VMs, I meant that I had upgraded the domain
ADMaster Posted April 9, 2014 Posted April 9, 2014 I’m not familiar with that gear, but can the two vlans route between each other. Your dhcp server is in a different subnet, but you do not provide that subnet / vlans configuration. Some switches you have to tag what vlans are allowed on the trunk port. If you go to vlan 60 or set yourself a static IP in the 10.101.60.0/24 range can you access dns then? With this being a new server install verify that the IP subnet is correct. When you enter an IP in the 10.x range it defaults it 255.0.0.0 or /8 you need 255.255.255.0 or /24 with the config you referenced above. Can other vlans access the dns server? If no other vlans can use dns see if the service is running or if there is any errors in event log. Also this is probably not the case with the no logon servers, but… Can your clients access the dns server but the dns server is not configured for forward the request? So effectively they do not have DNS. Nslookup is your friend, Cheers
DMcCoy Posted April 9, 2014 Posted April 9, 2014 Route issue, either the server or clients are not using the relevant switch IP for their gateway. DHCP requests are forwarded via the helper mechanism, the rest of the traffic is not.
jamesmay Posted April 10, 2014 Author Posted April 10, 2014 Ok so after doing suggested things: I have put wireshark on the DNS server. I can see the packet come in with the request from the IP address of the device and then go out. When the device is on the same subnet (VLAN60), all is good. If I put device onto VLAN70 DNS receives and makes reply but not reaching the device. When DNS is set to 8.8.8.8 then connects to site. Send a ping to the DNS, can see it come in and leave the server, but never reaches device. What is odd is that some devices on the 10.101.60.X/24 network can be pinged/ give me a route, but servers cannot... In my head this would be that a route does not exist from the 10.101.60.0/24 network to the others. This is what is configured on the switch: Gateway of last resort is 10.101.2.2 to network 0.0.0.0 Destination Gateway Dist/Metric Last Change ----------- ------- ----------- ----------- *S 0.0.0.0/0 via 10.101.2.2, Vl 2 1/0 00:00:05 C 10.101.2.0/24 Direct, Vl 2 0/0 2d19h C 10.101.10.0/24 Direct, Vl 10 0/0 8w6d C 10.101.20.0/24 Direct, Vl 20 0/0 8w6d C 10.101.25.0/24 Direct, Vl 25 0/0 8w6d C 10.101.30.0/24 Direct, Vl 30 0/0 8w6d C 10.101.40.0/24 Direct, Vl 40 0/0 8w6d C 10.101.41.0/24 Direct, Vl 41 0/0 8w6d C 10.101.50.0/24 Direct, Vl 50 0/0 8w6d C 10.101.60.0/24 Direct, Vl 60 0/0 8w6d C 10.101.70.0/24 Direct, Vl 70 0/0 8w6d
Duke5A Posted April 16, 2014 Posted April 16, 2014 You don't have multiple network adapters in the DNS server do you?
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now