Saturday, October 24, 2015

/32 subnets on Ethernet via DHCP




Is it possible to assign to an ethernet host via DHCP a subnet mask of only the host itself, e.g. 192.168.1.123/32? Do common operating systems support this kind of configuration?



I'd like for the hosts to send all of their traffic to the router (and not directly to some other host on the same segment), but still for them to be able to communicate (so no "client isolation"); effectively creating a point-to-point link, but without any client-side configuration.




Update: My intention is to configure a home router running dd-wrt so that all the traffic has to pass through the IP stack on the router, so it can be filtered by some ipfilter rules. I'd hoped for a general solution, some standard way to implement point-to-point Ethernet connections that still can be automatically configured by DHCP for all commons operating systems.



Based on the responses so far, this doesn't seem to be that easy; I'll read some more about VLANs and then reconsider my plans.


Answer



First of all, in order to create point-to-point link, you need at least 4 addresses, so you'll have to use a /30 mask. For example: 192.168.1.0/30




  • Network address: 192.168.1.0/30

  • 1st point address: 192.168.1.1/30


  • 2nd point address: 192.168.1.2/30

  • Broadcast address: 192.168.1.3/30



You'll have to place each host on a different /30 subnet and implement inter-subnet routing on your gateway.



Edit:
You don't write much about your infrastructure or the scalability you want to achieve with this configuration. I suppose your router supports the use of subinterfaces.



Also, no additional client-side configuration will be required if you use a DHCP server in order to distribute the addressing scheme.



No comments:

Post a Comment

linux - How to SSH to ec2 instance in VPC private subnet via NAT server

I have created a VPC in aws with a public subnet and a private subnet. The private subnet does not have direct access to external network. S...