Go to the router's admin interface status page and find out what DNS servers it got from your upstream ISP.
Read answer to: "HowTo: Find Out DNS Server IP Address Used By My Router?"
How do I find out my mail server blacklisted?
Free DNS Server
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Red Hat Linux Static Routing Configuration
How do I find out my Linux gateway / router IP address?
Router ARP Cache is Not Releasing Linux / UNIX Server IP address
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Redhat network interface configuration
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