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WSA & DNS

I have 3 internal dns with different priority but every time that the dns with priority 0 fail  or is not available , the navigation turns very slowly.

I think that the WSA is not able to knows that the DNS fail , and it keeps sending requests to the first DNS.

Any idea to solve this issue?

1 REPLY
Cisco Employee

WSA & DNS

Hi Oscar,

It seems there has already been enhancement request filed on this issue.

CSCzv11808    [Feature Request]: Failover for DNS servers

Symptom:

Latency in web requests when primary DNS server is down

Conditions:

WSA is configured for primary and secondary DNS servers. Primary DNS server is unresponsive and secondary DNS server is responding to web requests

Workaround:

Remove the primary(down) DNS server from the WSA configuration.

Customer wants the DNS servers to fail over to the second DNS server if the primary one is down like what we do for the AD servers.  Currently when we have 2 DNS servers configured with priority 0 and priority 1, we try the primary DNS server every time, wait for 5 sec and then switch to the secondary server. If the primary DNS server is down, we still try the same server for each and every connection and slowdown the entire Internet traffic by 5 sec unless we manually remove the primary DNS server.  Customer is requesting like a caching/intelligent algorithm where if we see the primary DNS server is non-responsive for like 5 min, then totally ignore this server and start talking to the secondary server right from start.  Note: From the CS perspective, I would say close to 50% of the slowness issue reported by customers belongs to this issue.

~BR
Jatin Katyal

**Do rate helpful posts**

~BR Jatin Katyal **Do rate helpful posts**
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