This configures an untagged connection, which is not the same as vlan
1. Also, there's no need to set that broadcast address manually, it's
inferred from the netmask.
auto eth1.2
iface eth1.2 inet static
address 192.168.100.254
netmask 255.255.255.0
vlan-raw-device eth1
I want vlan 1 to be the default hence I decared it as eth1 not eth1.1
That is most likely wrong. You set a "default interface" by configuring
the default gateway with the lowest metric. Other than that, there's no
"default" between network interfaces.