Dualhomed, sort of solved.

[Sidney_Kotic]

Basically, at this time, it looks to have almost completely came down to the
fight to get both Wicked and Network Manager happy along with different ways
yast works between 15.1 and 15.3.

I had to switch to Wicked to change ANYTHING in yast. Unfortunately after
exiting yast the network wouldn't work. Everything looked good (ip a, ip route,
netstat -nr, ifconfig, route -n) but the network was pretty much useless.
Go back to yast, switch to Network Manager (Note...making a change to something
and then switching back to Network Manager then exit...and the changes
disappear...make changes, exit, go back in switch to Network Manager, then exit
and the changes stay...loved this). At that point the WiFi (192.168.1.* on
wlan0) would generally work, but not eth0 (10.10.13.*). Fight with it a bit and
I've managed to get eth0 working. Then there was the netmask...yast kept trying
to assign a netmask of /32 for the 10.10.13.* network, changed it to /24 and
things seemed to settle down. Got me.

So, currently I have 3 computers running WiFi (ssh/rsync back and forth, plus
normal stuff to the internet) on wlan0 and cat-5 on eth0. Using the eth0
Computer A (the 15.1 machine) can ssh/rsync to computer B (a 15.3 machine), but
not Computer C (also a 15.3 machine). Computer B can ssh/rsync to Computer A
but not Computer C. Computer C can ssh/rsync to both Computer A and Computer B.
This tells me, and please tell me if I'm wrong, it's a firewall issue on
Computer C. Although I haven't spotted anything yet. I guess it's time to
fireoff wireshark, see who said what, and try to figure out where the firewall
logs are kept.

As a FYI the metrics are 100 for eth0 and 600 for wlan0.
bill@kraken:~> route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.1.1 0.0.0.0 UG 600 0 0 wlan0
10.10.13.0 0.0.0.0 255.255.255.0 U 100 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 600 0 0 wlan0

[William Unruh]

What machine is kraken?

> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 0.0.0.0 192.168.1.1 0.0.0.0 UG 600 0 0 wlan0
> 10.10.13.0 0.0.0.0 255.255.255.0 U 100 0 0 eth0
> 192.168.1.0 0.0.0.0 255.255.255.0 U 600 0 0 wlan0

The metrics do not matter. The paths to everything are unique.
Anything to tne net 198.168.1.x go onto wlan0 local network (Your
computer will ask for arp to find the ehternet addresses for any ip
address in that range.
Anything to 10.10.13.x goes onto eth0 local net
Anything else gets sent to 192.168.1.1 via wlan0
No idea why you think it is a firewall issue, but why not switch off the
firewall on C and see if things work.

Since you have not told us what the IP addresses are for A B and C, we
really cannot say anything.