Need some experienced feedback.

Recently I noticed some "quirks" with the quality of my network. Netflix signal would degrade or stop all together, frequent disconnects from streaming and gaming services on my PC. Called Comcast and they said NOTHING to worry about. I remained doubtful.

My networking knowledge is very limited but IM trying to learn more. so I mapped my network and then removed all wireless devices from it. Phones tablets etc The only thing left connected is my Ethernet connected PC. but when I run a "arp -a" from the commandline it shows 2 different internet addresses both with the same physical address. Both are dynamic. One of these is my PC, the other internet address shows FALLS Church Virginia. I have reset my modem, changed the name & password of my home network, changed the name of my ethernet connection and yet this internet address remains. Is there any reason for this? Comcast said they only saw my ip address as the one connected to the internet. it was my understanding that if there is only one device connected to the network there should only be 1 dynamic ip address showing up.

Why is this other dynamic address there? What could it reference? my modem? my router? Any help or just a point in the right direction would be much appreciated. THANKS. This is what I am seeing....

$ arp -a
.
Interface: 192.168.0.116 --- 0x8
Internet Address ..... Physical Address........Type

20.20.20.1 ...............00-1c-c0-6e-07-cb ...... dynamic
192.168.0.119 ..........00-1c-c0-6e-07-cb .......dynamic
192.168.1.255 ..........ff--ff-ff-ff-ff-ff...................static
.
.
My pc is the second dynamic address, why is that first one showing up if it is not a device that connected to my network ? 20.20.20.1 is a multicast address and isn't routable. It will usually be spoofed by routers but depending on how you connect them to the network a PC may determine that it should do so.========================
The IP address 20.20.20.1 was found in Falls Church, Virginia, United States. It is allocated to Computer Sciences Corporation. Additional IP location information, as well as network TOOLS are available below.
IP address:   20.20.20.1
ISP:    Computer Sciences Corporation
City:    Falls Church
Region:    Virginia
Country:    United States (US) flag
Postal code:    22042
Area code:    703
Metro code:    511
latitude:    38.864
longitude:    -77.1922
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20.20.20.1 Location Map

20.20.20.1
lat: 38.864
lon: -77.1922

Notes:
Computers connected to a network are assigned a unique number known as Internet Protocol (IP) Address.
IP (version 4) addresses consist of four numbers in the range 0-255 separated by periods (i.e. 127.0.0.1).
A computer may have either a permanent (static) IP address, or one that is dynamically assigned/leased to it.

Most IP addresses can be mapped to host/domain names (i.e. www.speedguide.net).
Resolution between domain names and IP addresses is handled by Domain Name Servers (DNS).
======================
The above is from:
https://www.speedguide.net/ip/20.20.20.1
I think this is not accurate.