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DNS responses are blocked as DoS attacks

  • palych
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01 May 2013 10:29 #76015 by palych
H Everyone

I am experiencing an issue on a Vigor 2850n router, where at some stage it stops passing DNS responses into the network which stops resolving websites on all internal devices and SBS2008 server. Skype and all applications which do not rely on dns are fine.

Mail Alert from Router shows the following:

2013/04/30 17:02:48 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:36215][UDP][HLen=20, TLen=387]
2013/04/30 17:02:50 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.220.220:53->xxx.xxx.xxx.xxx:55677][UDP][HLen=20, TLen=80]
2013/04/30 17:02:51 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:36215][UDP][HLen=20, TLen=387]
2013/04/30 17:02:53 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:59538][UDP][HLen=20, TLen=192]
2013/04/30 17:02:55 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:37253][UDP][HLen=20, TLen=136]
2013/04/30 17:02:57 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:51125][UDP][HLen=20, TLen=114]
2013/04/30 17:02:59 -- [DOS][Block][udp_RP_flood, timeout=10][208.67.222.222:53->xxx.xxx.xxx.xxx:64777][UDP][HLen=20, TLen=186]

where xxx.xxx.xxx.xxx is our public IP

obviously i can stop this by stopping DOS protection, which i dont really want to do, so would you recommend something to tackle this issue please

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07 May 2013 14:27 #76077 by sicon
Log it with Draytek support.
You could also allow port 53 though the firewall, that should override the DOS defense

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12 May 2013 22:27 #76168 by palych
Thank you

I have increased threshold and it stopped appearing

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