I recently had to change from fios to comcast and now I can’t seem to ping any of my computers from within my own network. Any suggestions on where to look to fix this?
What exactly is your setup. Is it something like this?
comcast cable modem -----> router and/or switch -------> your computer
Pudge
mycomputer:
comcast modem/wireless router → my computer
the computer I am trying to reach:
comcast modem/wirelessrouter → switch → computer2
Perhaps after you switched over a cable was inserted into the wrong port?
already checked all the wires to make sure they are all correct
If you changed the router/gateway, it is possible that the DHCP is delivering another RFC1918 address space.
Can you confirm if both computers are getting IP from the DHCP, or are they using static IPs that was set before you swapped the router/gateway?
yes both computers ares getting addressed from DHCP. Here are the relevant address from ip address
mycomputer:
10.0.0.71/24 brd 10.0.0.255 ```
computer2:
10.0.0.188/24 brd 10.0.0.255
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Be careful what you post 
They are in the same subnet.
This ping should be going through the switch and not even reaching the router/gateway.
The packet would flow from computer1 > wireless router > switch > computer 2
It would work even without a gateway set…
always good advice, I didn’t think there was anything unsafe there, is there something I should be aware of?
He is right @galvez_65, ipv6 information, erase it..
that’s what I thought as well, which is why this is driving me nuts.
Do you have ufw installed? Maybe its blocking ICMP
I have firewalld installed, temporarily stopping it does nothing
Ok, is that wireless router running in AP mode?
Is internet working, just ping between computers that it isn’t?
|| erased the previous info that could lead to confusion ||
ok I took the comcast router out of the equation and now the only DHCP addresses are coming from my mesh pods. Yes the internet is working, I just can’t ping any of the other computers.
If you took “my computer” and hooked it into the switch, and still couldn’t ping the other computers? If so.
The comcast xfi cable modem uses 10.0.0.1 for the LAN side IP. “My computer” might have it’s gateway IP and DNS servers IPs set to 10.0.0.1.
But then when you connect “My Computer” to the switch, check some of the other computers and see what their gateway IP and DNS servers IPs are set to. Perhaps 192.168.0.1 ?
Plus, if your setup is like this
|-------------| ___________
| 10 N -----| ----O wifi O---| my computer|
| .0 A | ------------
| .0 T -----| ------| |--------|
| .1 | |--------| Switch |------ other computer
| cable modem | | |------ other computer
--------------- ----------
As far as I know, It won’t work as you want it to. In order for “My Computer” which comes into
the WiFi receiver and then goes through the NAT hardware firewall, it would then need to go back through the NAT hardware firewall to get to the switch. NAT will not allow that. This is a security issue so that someone sitting in a van in front of your house cannot get into the WiFi section of the cable modem then go right into your switch.
You just proved that a weird person in a van can’t pull up in front of your dwelling, hack into your WiFi then get into your LAN server. He can however still go on the internet to a certain no-go site and have the Feds show up at your home asking questions about who at this IP was at this no-go site
Pudge
EDIT:
I know that
is not a fool proof statement. There are people out there that can hack back into your LAN in this circumstance, but it eliminates most hackers and only the best hackers or a three letter organization can accomplish this.
Same subnet - but -but - but - check your network config for user isolation.
In Denmark public institutions like libraries, hostpitals etc. often provides free internet access - regulated by SSI and the network isolates all users to make it more difficult to use the networks as attack vectors.
Network isolation can be done in a number of ways such as segmentation, segregation, VLAN or firewalling.
Since you are only encountering the issue after switching provider - and most likely router - it is reasonable to assume it is a router setting since a router will route any traffic it receives within the defined subnet.
I still can’t seem to resolve any computer name on my network. After @anon49550872 comment on making sure they were all on the same DHCP I changed my config to be as follows:
Comcast modem --> deco mesh wifi router --| ---wifi -- > my computer
| --- switch ---> backup server
pinging IP address instead of the hostname is working?