Dividing the subnet

[MAHESH.K]

Hi,

  We have been given /29 subnet by the isp. Can it be divided into still smaller subnets?

Mahesh

[Karsten Iwen]

As always: It depends ...

1. This is the subnet between the ISP-device and your router/firewall: No, you can't.
2. This is an additional subnet that the ISP routes to your router/firewall: Yes, you can divide it in two /30 networks and use them for example on different internal interfaces.

[MAHESH.K]

Hi,

    This is the only subnet given by isp. one more thing, can i use this public ip block given by ISP to both WAN interface and two different internal networks?

[Karsten Iwen]

When this network is configured on the WAN-side of your router/firewall. You can only use it there. But addresses of that /29 can be used with NAT to point to any internal system. That could be in different internal networks.

[Karsten Iwen]

And to add to 2):

You would reduce you valuable public address-space from five usable addresses to two addresses. If your plan is to separate servers, you could also put them all into one subnet and do the separation on the switch-level with port-ACLs, private VLANs or private VLAN Edge.