How to treat broadcast ip address as a normal IP

Question

I'm new to networking things. I have a sub-network with 16 IPs (ex: 1.2.3.0 to 1.2.3.15). I'm using lxc for each IP for different purposes, but currently the containers with IP 1.2.3.0 and 1.2.3.15 cannot communicate with other containers in my subnetwork although it can communicate with anything else on the internet. And other containers (from 1.2.3.1 to 1.2.3.14) cannot communicate with 1.2.3.0 and 1.2.3.15 as well. How to solve this problem? The containers use ubuntu 18.04, host also uses ubuntu 18.04.

Here is the lxc config:

lxc.include = /usr/share/lxc/config/common.conf
lxc.mount.entry = /sys/kernel/debug sys/kernel/debug none bind,optional 0 0
lxc.mount.entry = /sys/kernel/security sys/kernel/security none bind,optional 0 0
lxc.mount.entry = /sys/fs/pstore sys/fs/pstore none bind,optional 0 0
lxc.mount.entry = mqueue dev/mqueue mqueue rw,relatime,create=dir,optional 0 0
lxc.arch = linux64
lxc.rootfs.path = dir:/var/lib/lxc/con0/rootfs
lxc.uts.name = con0
lxc.net.0.type = veth
lxc.net.0.link = lxcbr0
lxc.net.0.flags = up
lxc.net.0.ipv4.address = ...
lxc.net.0.ipv4.gateway = ...
lxc.net.0.hwaddr = ...

Implement IPv6 which has an enormous number of addresses per subnet. (And happens to replace broadcast with multicast, doing away with network and broadcast IPs.) — John Mahowald, Jul 04 '20 at 02:25

score 3 · Accepted Answer · answered Jul 03 '20 at 22:48

It sounds like you are using a /28 subnet with a netmask of 255.255.255.240. In that case:

.0 is the network address .15 is the broadcast address

These cannot be used as host IPs because as you have found other hosts on that same subnet will struggle to communicate.

If you need more hosts you need to increase the network size.

The next size up would be /27 with a netmask of 255.255.255.224, that would give you 30 usable host IPs with .0 still being the network address and .31 being the broadcast.

How to treat broadcast ip address as a normal IP

1 Answers1