vlan segregation

[jagdev.dhaliwal]

Hi frds

i have a subnet of 10.24.22.1/24, i want to futher segregat it so that i can get around 30 hosts in a subnet and around 170 hosts in other . Is it possible and if it is, than how ?

can u guys help me

Jagdev

[Jon Marshall]

Hi Jagdev

No it is not possible. You can get the 30 host subnet but you can't get the 170 host subnet because the largest you could support would be a /25 ie.

10.24.22.0 255.255.255.128

which gives hosts

10.24.22.1 -> 10.24.22.126 + broacast of 10.24.22.127.

Jon

[Kevin Dorrell]

Jagdev,

As Jon says, it is not possible to divide the address space asymetrically because you have to split it on a bit boundary. However, if your objective is to split the space into two VLANs, there is a slightly messy trick you could use: split it three ways (one /25 and two /26) and put two subnet (the /25 and a /26) on one VLAN.

In the following example, VLAN 221 handles the address space from 10.24.22.0 to 10.24.22.63, and VLAN 222 handles the address space from 10.24.22.64 to 10.24.22.255.

int vlan 221

ip address 10.24.22.1 255.255.255.192

!

int vlan 222

ip address 10.24.22.65 255.255.255.192

ip address 10.24.22.129 255.255.255.128 secondary

Of course, you have to avoid issuing addresses that conflict with any of the base addresses, gateway addresses, or directed broadcast addresses.

For the hosts in VLAN 222, there are two ways you could configure them:

1. You could give them different gateway addresses depending on which subnet they fall into,

2. You could give them all a /24 mask and tell them to use 10.24.22.65 or 10.24.22.129 as gateway - it doesn't matter which. In this case, if they wanted to talk to any hosts in VLAN 221, they would be relying on proxy-arp responses from the switch.

Kevin Dorrell

Luxembourg