qemu-amd64: can't connect to the internet

qemu-amd64:~$ wget http://dl-cdn.alpinelinux.org/alpine/edge/main/x86_64/APKINDEX.tar.gz
Connecting to dl-cdn.alpinelinux.org (151.101.112.249:80)
wget: can't connect to remote host (151.101.112.249): Network unreachable

Running ip route add default via 172.16.42.2 (or route add default gw 172.16.42.2) fixes the problem:

qemu-amd64:~$ wget http://dl-cdn.alpinelinux.org/alpine/edge/main/x86_64/APKINDEX.tar.gz
Connecting to dl-cdn.alpinelinux.org (151.101.112.249:80)
APKINDEX.tar.gz      100% |*****************************************************************************|  761k  0:00:00 ETA