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17.7 Legacy Series / [SOLVED] Cannot ping ISPs DNS servers since upgrade from 17.1.11 to 17.7

« on: August 05, 2017, 11:14:40 pm »

Hi,

since the upgrade from 17.1.11 to 17.7 I cannot resolve external hostnames anymore.

My network:
Internet <--> ISP box (in routing mode, DHCP server enabled) <--> OPNsense box (retrieves DNS server IPs per DHCP from the ISP box) <--> Clients

After some troubleshooting I found out that the OPNsense box is unable to ping my ISPs DNS servers.

There are two weird entries in the routing table of my OPNsense box:

Code: [Select]

Destination        Gateway            Flags     Netif Expire
195.34.133.21      00:0d:b9:XX:XX:XX  UHS        igb1
212.186.211.21     00:0d:b9:XX:XX:XX  UHS        igb1The IPs are the two DNS servers from my ISP, and the gateway is the MAC address of the igb1 interface of my OPNsense box.
Shouldn't the gateway point to the IP/MAC of the ISP Box?

There are also two weird ARP entries:

Code: [Select]

? (195.34.133.21) at (incomplete) on igb1 expired [ethernet]
? (212.186.211.21) at (incomplete) on igb1 expired [ethernet]The ISPs DNS server is obviously not in my local network, why does the OPNsense box have an ARP entry for it?

When I delete the two routes for the ISPs DNS servers manually, I can ping the DNS servers from the OPNsense box again and everything works. But this route gets recreated on each boot.
Has anybody a tip what's the issue here?


Thanks,
Andreas