>
> 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
> >
> > The problem is this one.
> > I use /etc/hosts to put a name to each PC connected to A.
> > PC A is normally always started first.
> > If PC B and PC C are started always in the same order, there is no problem.
> > But if I change the starting order, then I cannot connect to them from PC A.
> > Initially, I configured Automatic DHCP on both (PC B and PC C).
> > To avoid the issue, I set the configure Manually, but it does not really
> > solve the issue.
> > It seems that PC A configures the interface connected to PC C in 10.42.0.1
> > if
> > PC C is started before PC B, and in 10.42.1.1 if PC C is started after PC B.
> > In theory, I should not care, but it seems that if PC C is connected first
> > to the interface
> > then it is set in 10.42.0.1, then PC C address has to be something like
> > 10.42.0.204
> > while if the interface has been set in 10.42.1.1, PC C address has to be
> > like 10.42.1.204.
> >
> > How can I solve this issue?
> > On PC A: Do I need to switch from shared to other computers to Manual?
> > If Yes how should I configure ?
> > 10.42.1.0 255.255.255.0 Gateway? DNS ?
> >
> > Thank.
>
>
> Hi Patrick,
>
> Did you ever get this solved?
>
> I personally would have used a hub to connect
> everybody up. Five port layer two switching hubs
> are pretty cheap no-a-days.
>
> https://www.trendnet.com/products/gigabit-switch/5-port-gigabit-desktop-switch-TEG-S51
>
> Or if you want an external firewall, which induces
> the hub, this is a bit more expensive and requires
> a bit of firewall knowledge to operate:
>
> https://www.watchguard.com/wgrd-products/tabletop/firebox-t25
>
> If not, then:
>
> 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
>
> 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
enp0s20f0u11
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 bridge0
10.40.0.0 0.0.0.0 255.255.255.0 U 0 0 0 bridge0
10.42.0.0 0.0.0.0 255.255.255.0 U 0 0 0 enp1s0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0
enp0s20f0u11
192.168.1.1 0.0.0.0 255.255.255.255 UH 0 0 0 bridge0
192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0
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
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
>
> -T
>
> --
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