On 6/16/25 12:25 PM, Patrick Dupre via users wrote:
On 6/14/25 11:28 AM, Patrick Dupre via users wrote:
Hello,
I tried to fix a small issue that I have.
PC A is connected to internet through a USB port.
This PC A has 2 RJ45 cards, connected to 2 PC: B and C.
Both interface are in shared to other computers
I do not know if this will help you or not, but
to get ports to forward, I run this inside my
iptables firewall:
# Check and force Masquerading
MasqStatus=`cat /proc/sys/net/ipv4/ip_forward`
if [ "$MasqStatus" = "0" ]; then
echo 1 > /proc/sys/net/ipv4/ip_forward
logger -p user.notice -t firewall "Warning: IP FORWARDing forced."
fi
On PC A
cat /proc/sys/net/ipv4/ip_forward
1
On PC B and PC , it is 0
That's correct. You should not have to touch any of that yourself.
Network manager will handle it all if the interfaces are configured
correctly.
Just try the (as root)
# echo 1 > /proc/sys/net/ipv4/ip_forward
by itself
Also, would you open a terminal and post the following
for both working and not working?
netstat -rn
It will show who is up and who is down, plus who is
acting as a gateway. It will let us all know
what exactly is going on.
# netstat -rn
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 bridge0
192.168.1.1 0.0.0.0 255.255.255.255 UH 0 0 0 bridge0
These shouldn't be there, so there's something wrong with the bridge config.
It seems tha because of the bridge enp2s0 does not show up
bridge0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.40.0.1 netmask 255.255.255.0 broadcast 10.40.0.255
inet6 fe80::c7db:7630:ffac:a47c prefixlen 64 scopeid 0x20<link>
ether 88:d7:f6:c5:a3:9d txqueuelen 1000 (Ethernet)
RX packets 8976 bytes 674062 (658.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 29742 bytes 1328396 (1.2 MiB)
TX errors 0 dropped 37 overruns 0 carrier 0 collisions 0
enp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether 88:d7:f6:c5:a3:9d txqueuelen 1000 (Ethernet)
RX packets 9079 bytes 809699 (790.7 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 49404 bytes 2353481 (2.2 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 10.42.0.1 netmask 255.255.255.0 broadcast 10.42.0.255
inet6 fe80::4983:5a2d:430d:2dd9 prefixlen 64 scopeid 0x20<link>
ether 50:91:e3:c9:58:ab txqueuelen 1000 (Ethernet)
RX packets 29828 bytes 3436837 (3.2 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 48392 bytes 45933193 (43.8 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
enp1s0 should not have an IP address.
It also seems that 10.40.0.0 has been created when I configured the bridge between enp1s0 and enp2s0
Right now I have
PC B as 10.42.0.82 (configured manually) and it works fine (DNS OK and it can be reached from PB A)
and
PC C as 10.40.0.204 (configured manually) and it works fine (DNS OK and it can be reached from PB A)
but PC B can reach PC A and verse and versa
The bridge is probably not set properly
You still have enp1s0 configured somewhere. You need to remove that.
PC B should be on 10.40.0.x as well.
--
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