virsh / Failed to start network default

I've been scouring google for the past day trying to figure out why I can't create a default network for my linux guest. One source says the iptables error is harmless, but I still can't create a default network. What's going on here?

the default.xml didn't even exist on my filesystem, so I had to copy it from a forum.

Code:# pwd
/usr/share/libvirt/networking

# virsh net-undefine default
Network default has been undefined

# virsh net-destroy default
error: failed to get network 'default'
error: Network not found: no network with matching name 'default'

# virsh net-list
Name State Autostart Persistent
----------------------------------------

# cat default.xml
<network>
<name>default</name>
<uuid>afd4e923-66cb-45ca-9120-1e46e72899a3</uuid>
<forward mode='nat'>
<nat>
<port start='1024' end='65535'/>
</nat>
</forward>
<bridge name='virbr0' stp='on' delay='0'/>
<ip address='192.168.122.1' netmask='255.255.255.0'>
<dhcp>
<range start='192.168.122.2' end='192.168.122.254'/>
</dhcp>
</ip>
</network>

# virsh net-define default.xml
Network default defined from default.xml

# virsh net-autostart default
Network default marked as autostarted

# virsh net-start default
error: Failed to start network default
error: internal error: Failed to apply firewall rules /sbin/iptables -w --table filter --insert LIBVIRT_INP --in-interface virbr0 --protocol tcp --destination-port 67 --jump ACCEPT: iptables: No chain/target/match by that name.Code:# uname -a
Linux user-pc 5.3.0-45-generic #37-Ubuntu SMP Thu Mar 26 20:41:27 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

# cat /etc/issue
Ubuntu 19.10 \n \l