Visitor
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3 Messages
DNS server question
Hi there,
I have a question regarding Comcast DNS server addresses: When looking in the Xfinity Network section of my rented XB8-Techicolor the IPV4 DNS primary server 1 is 75.75.75.75 and the IPV4 DNS secondary server is 75.75.76.76. The IPV6 DNS primary server is 2001:558:feed::1 and the secondary IPV6 address is 2001:558:feed::2 .
Out of curiosity I did a 'what's my DNS server test' and it gave a different result. It showed my IPV4 DNS servers were 76.96.24.1, 76.96.24.3, 76.96.24.21, and 76.96.24.7 . It showed my IPV6 DNS addresses were 2001:558:fee0:8320:76:96:24:3 , and 2001:558:fee0:8320:76:96:24:1 . All of the addresses shows as located in Ashburn, USA.
Why would there be a difference like this? Thanks in advance!
BruceW
Gold Problem Solver
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26.8K Messages
29 days ago
The addresses in your first paragraph are Anycast addresses (see https://en.wikipedia.org/wiki/Anycast). Anycast is basically a method for steering requests to to the "closest" server. The addresses of the actual DNS servers are the ones in your second paragraph. It looks odd, but it's normal for Anycast routing.
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XfinityJeff
Official Employee
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249 Messages
27 days ago
Good morning @user_3b9548, I hope you are having a good weekend. Many routers have a built-in DNS server (sometimes named dnsmasq) that caches DNS requests. When your devices query the DNS server listed for them, they are actually querying your router's IP address, which then forwards the request to the primary/secondary DNS servers that your router is configured to use.
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EG
Expert
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113.9K Messages
27 days ago
@XfinityJeff
While that is true for most models, a router that is doing DNS relay / forwarding of the DNS IP addresses are typically the private / non-routable IP address of the gateway (192.168.xxx or 10.0.0.x). The poster's DNS IP addresses that are being shown being shown are public / routable IP addresses that belong to Comcast.
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