I have been following two other threads on same topic but unable to resolve my issue.
On 11-5-2012 my users complained of "internet down" and subsequent investigation pointed at DNS failure. Further observation was that it was intermittant without rhyme or reason. Affecting different target external sites without exception and then starting to work again without intervention.
We have swapped routers, the ISP has swapped their interface device but problem persist.
Network overview is Cbeyond IAD with bundled voice/data services (T-1). 5 Public IP addresses.
Netgear FVS336G2v2 with latest firmware assigned xxx.xxx.xxx.106 IP. Cbeyond Gateway xxx.xxx.xxx.105. LAN side is 10.0.1.0 with router assigned 10.0.1.254. Port forwarding set up for RDC and VNC and 2 IPSEC tunnels derived. The workstations behind router are all XP Pro SP3 with Dell T610 RAID 1/5 Server 2008R2 as Domain Controller and DNS active (10.0.1.10). All workstations are configured to point to 10.0.1.10 for DNS. Forwarders on DNS set to Cbeyond DNS with 64.238.96.12 as primary and 66.180.96.12 as secondary. After reading prior threads I ran nslookup and got response of <512 bytes. I then added L3 DNS (4.2.2.2) and elevated it to first choice and got nslookup results of reply size limit at least 3048.
Still having resolution issues so I made 4.2.2.2 the only forwarder and still have intermittant DNS resolve/load.
I am willing to document anything required to get assistance in resolving this. Please advise what to test, inwhat order and how to get the results to you.
Thanks in advance