Comcast / Xfinity DNS Servers (75.75.75.75) & How to Change

What Are Comcast / Xfinity DNS Servers?

Comcast/Xfinity's DNS servers are 75.75.75.75 and 75.75.76.76 (IPv6: 2001:558:feed::1 and 2001:558:feed::2). Your Xfinity gateway hands them to every device automatically, and they turn names like google.com into the IP addresses your devices connect to.

They are private to Comcast's network: from another ISP they don't answer at all. Whether a public resolver is faster depends on where you are (Comcast's resolvers sit inside its own network, which often makes them quick), so measure it from your own connection with DNS Robot's DNS Speed Test before you change anything.

Comcast / Xfinity DNS Server IP Addresses (IPv4)

Here are Comcast's default DNS server addresses, assigned automatically to Xfinity residential Internet customers nationwide.

Comcast's own reverse DNS names them: 75.75.75.75 is cdns01.comcast.net and 75.75.76.76 is cdns02.comcast.net, both registered to Comcast Cable Communications.

They only answer queries from Comcast's network. Set them on a connection from another ISP and every lookup times out, which is why "DNS 75.75.75.75" fails for people who copy it from a forum while on a different provider.

Xfinity IPv6 DNS Servers

Comcast has one of the largest IPv6 deployments of any U.S. ISP, and IPv6 is enabled by default on most Xfinity gateways. Here are the Comcast IPv6 DNS resolver addresses.

The IPv6 pair belongs to the same two servers (cdns01 and cdns02.comcast.net). If you switch to another provider, change both your IPv4 and IPv6 DNS: leaving IPv6 on Comcast while changing only IPv4 sends some lookups to Comcast anyway.

Cloudflare's IPv6 DNS servers are 2606:4700:4700::1111 and 2606:4700:4700::1001; Google's are 2001:4860:4860::8888 and 2001:4860:4860::8844.

Comcast Business DNS Servers

Comcast Business customers use the same 75.75.75.75 / 75.75.76.76 DNS infrastructure by default. Business accounts can also order static IP addresses and run their own resolvers for custom domain and mail configurations.

If you run a business on Comcast, consider a security-focused public resolver such as Quad9 (9.9.9.9) or Cloudflare's malware-blocking 1.1.1.2. These filter known malicious domains at the DNS layer, adding protection without installing anything on each device.

Static-IP plans need their reverse DNS (PTR records) set through Comcast Business support; check them with DNS Robot's Reverse DNS tool.

Why Change Xfinity's Default DNS?

Comcast's DNS works fine for everyday browsing, but there are solid reasons to switch to a public resolver.

One quick sanity check before you start: if you're on a reseller plan, building WiFi, or mobile data, you may not actually be on Comcast's network at all. Check your ISP first — it shows the network and ASN really carrying your traffic, so you change the right settings.

• Speed, sometimes — a public resolver can be faster or slower than Comcast's depending on your area: test both with the DNS Speed Test before you switch
• Better uptime — Public resolvers run large global networks built for redundancy. ISP DNS outages, when they happen, can take a whole region offline
• Privacy — Cloudflare's 1.1.1.1 keeps no source IP address on disk and deletes its logs within 25 hours, and an outside accounting firm audits that. ISP DNS data handling is governed by Comcast's broader privacy policy
• No NXDOMAIN redirection — Some ISPs have historically redirected mistyped/unknown domains to a branded search page. Switching DNS guarantees you get a clean NXDOMAIN instead
• Built-in security — Quad9 (9.9.9.9) blocks known malware and phishing domains; Cloudflare for Families (1.1.1.3) blocks malware and adult content at the DNS level
• Encryption support — Public resolvers support DNS-over-HTTPS and DNS-over-TLS, so your lookups can't be read or modified on the network

Best DNS Servers for Xfinity Users

These are the best public DNS alternatives for Comcast/Xfinity customers, ranked by speed, privacy and features. All are free and work with any Xfinity plan.

For most Xfinity users, Cloudflare (1.1.1.1) is the best overall pick for privacy: it keeps no source IP on disk, deletes its logs within 25 hours, and has that audited. Want malware filtering? Quad9 (9.9.9.9). Want a cleaner, ad-light network? AdGuard DNS. Full address lists and setup steps: our Cloudflare DNS servers guide and Google DNS servers guide.

Don't guess which is fastest for you — the closest resolver depends on your city and Comcast region. Run DNS Robot's free DNS Speed Test to benchmark Cloudflare, Google and Quad9 from your own connection and pick the real winner.

How to Change DNS on an Xfinity Gateway

This is where Xfinity differs from most ISPs: Xfinity gateways (XB6, XB7, XB8 and newer) don't let you change the DNS servers they hand to your devices. Below are the three ways that work, from quickest to most thorough.

Method 1: Check the Admin Tool (10.0.0.1)

First, confirm what your gateway allows. A few older or customer-owned modems do expose a DNS field.

• Step 1 — In the Xfinity app, turn on Admin Tool access: WiFi tab → View WiFi equipment → Advanced settings → Admin Tool online access → Allow Admin Tool access → Save (XB6, XB7, XB8 and XB10). First-time setup asks you to create a new admin password
• Step 2 — Go to 10.0.0.1 from a device on your Xfinity network and sign in as admin with that password (if you turned access on before February 2026, the default password on the gateway's sticker may still work)
• Step 3 — Look under Gateway → Connection → Local IP Network (labels vary by model) for a DNS field
• Step 4 — If there's none, or it's greyed out, use Method 2 (per device) or Method 3 (Bridge Mode)

Method 2: Set DNS Per Device

Because the gateway often locks DNS, the most reliable approach is to set DNS on each device. It takes a minute per device and overrides what the gateway hands out; confirm it worked with the DNS Leak Test. Jump to the Windows, Mac or mobile steps below.

Method 3: Bridge Mode + Your Own Router

For full, network-wide control, put the Xfinity gateway into Bridge Mode and connect your own router (TP-Link, ASUS, Netgear, eero). Your router then handles DHCP and DNS, so you can set any resolver once for every device.

• Step 1 — In the Admin Tool (10.0.0.1), go to Gateway → At a Glance and click Enable next to Bridge Mode. The gateway may restart
• Step 2 — Connect your own router to an Ethernet port on the gateway and set it up
• Step 3 — In your router, set the DNS servers to your choice (for example 1.1.1.1 and 1.0.0.1)
• Step 4 — Reboot and confirm with the verification steps below

Change DNS on Windows (Xfinity Connection)

Setting DNS on Windows overrides the gateway's DNS for that PC. Here's how on Windows 11 and 10.

Changing DNS on Windows needs administrator rights: run PowerShell as Administrator for the commands below.

• Step 1 — Open Settings → Network & internet → Wi-Fi → Manage known networks → your network (for a cable: Ethernet → your network)
• Step 2 — Click Edit next to DNS server assignment
• Step 3 — Switch from Automatic (DHCP) to Manual, then turn on IPv4
• Step 4 — Preferred DNS = 1.1.1.1, Alternate DNS = 1.0.0.1 (Cloudflare)
• Step 5 — (Optional) Turn on IPv6 and add 2606:4700:4700::1111 / 2606:4700:4700::1001, then Save

# PowerShell: set DNS on the active adapter
$adapter = Get-NetAdapter | Where-Object {$_.Status -eq 'Up'} | Select-Object -First 1
Set-DnsClientServerAddress -InterfaceIndex $adapter.ifIndex -ServerAddresses '1.1.1.1','1.0.0.1','2606:4700:4700::1111','2606:4700:4700::1001'

# Flush the resolver cache and verify
Clear-DnsClientCache
Get-DnsClientServerAddress -InterfaceIndex $adapter.ifIndex

Change DNS on Mac (Xfinity Connection)

macOS lets you override DNS per network service in a few clicks.

• Step 1 — Open System Settings → Network → select your active connection (Wi-Fi or Ethernet)
• Step 2 — Click Details → choose DNS from the sidebar
• Step 3 — Click + and add 1.1.1.1 and 1.0.0.1
• Step 4 — Remove any existing Comcast DNS entries (75.75.75.75) with −
• Step 5 — Click OK

# Terminal: set DNS for the Wi-Fi service
networksetup -setdnsservers Wi-Fi 1.1.1.1 1.0.0.1

# Flush the DNS cache
sudo dscacheutil -flushcache && sudo killall -HUP mDNSResponder

# Verify and test resolution
networksetup -getdnsservers Wi-Fi
dig @1.1.1.1 google.com +short

Change DNS on iPhone & Android (Xfinity Wi-Fi)

If the gateway locks DNS, override it on your phone instead.

iPhone / iPad

• Step 1 — Settings → Wi-Fi → tap the (i) next to your Xfinity network
• Step 2 — Scroll to Configure DNS → switch from Automatic to Manual
• Step 3 — Delete existing entries, then Add Server → 1.1.1.1 and 1.0.0.1
• Step 4 — Tap Save

Android (Private DNS)

Android 9+ has a global Private DNS feature that applies encrypted DNS everywhere — including Xfinity Wi-Fi and mobile data.

• Step 1 — Settings → Network & Internet → Private DNS
• Step 2 — Select Private DNS provider hostname
• Step 3 — Enter one.one.one.one (Cloudflare) or dns.google (Google)
• Step 4 — Tap Save

How to Verify Your DNS Changed

After changing DNS, confirm your device is actually using the new servers.

# Windows — show the resolver in use
nslookup google.com
# The "Server:" line should show 1.1.1.1, not 75.75.75.75.
# After a router change (Bridge Mode) it may show your router's IP: the DNS Leak Test shows the real resolver

# Mac/Linux — compare response times
dig google.com @1.1.1.1 | grep "Query time"     # Cloudflare
dig google.com @75.75.75.75 | grep "Query time" # Comcast: compare the two Query time lines

For a visual, side-by-side comparison from your own browser, run DNS Robot's DNS Speed Test — it ranks the major resolvers by real latency so you can confirm the one you picked is actually faster than Comcast's.

If nslookup still shows 75.75.75.75, flush your DNS cache and restart your browser. A router-level change reaches each device when it renews its connection: turn Wi-Fi off and on to speed that up.

Common Xfinity DNS Issues & Fixes

Comcast DNS occasionally has slowdowns and outages. Here are the most common problems and how to solve them.

Comcast DNS Server Not Responding

Your browser shows "DNS server not responding" or DNS_PROBE_FINISHED_NXDOMAIN while the gateway shows a solid connection. First find out whether Comcast's DNS is the problem: ask Comcast's server and a public one for the same name.

# Ask Comcast's resolver, then Cloudflare's, for the same name
nslookup example.com 75.75.75.75
nslookup example.com 1.1.1.1

# Comcast fails, Cloudflare answers  → Comcast's DNS is the problem: switch DNS
# Both fail                          → your connection is down: restart the gateway

Then fix it in this order:

• Switch DNS — set Cloudflare (1.1.1.1) or Google (8.8.8.8) on your device to bypass Comcast's resolvers
• Restart the gateway — unplug it for 30 seconds, plug it back in, and wait 2–3 minutes
• Flush the DNS cache — ipconfig /flushdns on Windows or sudo dscacheutil -flushcache on Mac (all systems)
• Check for an outage — the Xfinity app's status, or Downdetector Xfinity. For more, see how to fix DNS server not responding

Slow DNS Lookups on Xfinity

If sites pause before loading but then download quickly, slow DNS is a likely cause: a single page can trigger dozens of lookups, and each one waits for the resolver.

Measure before you switch: DNS Robot's DNS Speed Test times Cloudflare, Google, Quad9 and others from your own connection, and the Ping tool compares raw latency. Pick the fastest one for your area.

xFi Gateway Won't Let Me Change DNS

This is the most common Xfinity complaint: there's no DNS field at 10.0.0.1, or it's greyed out. Xfinity gateways don't let you change the DNS they hand out.

Your options:

• Set DNS per device — Override on each computer, phone, console and TV (see the steps above). The fastest path for most people
• Use Bridge Mode + your own router — Full network-wide control over DNS and every other setting
• Android Private DNS — Forces encrypted DNS at the OS level regardless of the gateway
• Browser DoH — Chrome, Edge and Firefox can use DNS-over-HTTPS, bypassing the gateway's DNS for web traffic only