Just a questions on this. This seems simple but doesn't make sense to me. I have seen engineers who have an IP of 192.168.100.1/26 for an SVI address. My question is if you are going to use a /26 why would you use .1 as your SVI IP? Shouldn't you use 192.168.100.65/26? Doesn't this defeat the purpose of using a /26? Isn't 192.168.100.1 on another network? Thanks for any response
0 - 63
64 - 127
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
In no event shall Author be liable for any damages wha2tsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Unclear you confusion. 192.168.100.1/26 is indeed in a different network from 192.168.100.65/26. 192.168.100.1/26 is the first IP in its /26 network, as 192.168.100.65/26 is the first in the next /26 network.
Your question needs clarification. 192.168.100.1/26 is the first address on the 192.168.100.0/26 network and so is a valid address to use. 192.168.100.65/26 is the first address on the 192.168.100.64/26 network. so you can have the following configuration:
interface vlan 10
ip address 192.168.100.1 255.255.255.192
interface vlan 20
ip address 192.168.100.65 255.255.255.192
Would that be the first address because the address is a class C and should be a /24 and since we are moving over the bits to a /26 the 192.168.100.0 would be covered under this?
192.168.100.1 255.255.255.192 is the SVI for VLAN10
Should I start my dhcp at 192.168.100.10 or start at 192.168.100.65. It seems I should start with the .65 since I am using a /26.
192.168.100.65 is in a different network to 192.168.100.1 Since SVI for vlan 10 is 192.168.100.1 your dhcp range would be from 192.168.100.2 - 192.168.100.62
Have a look at the following doc that explains a little about subnets:
The default subnet mask for a Class C address is /24 which will give you 192.168.100.1 through 192.168.100.254 as usable addresses.
If you choose not to use the default mask of /24, you can split that /24 subnet up into four /26 subnets. Exactly four /26 subnets make up a /24 subnet, although that may not be the best way of thinking about it if you are learning :)
If you want to use 192.168.100.0 as your example and you wanted to use a /26 mask, you would end up with the following subnets:
192.168.100.1 - 192.168.100.62 for hosts
192.168.100.63 is broadcast address
192.168.100.65 - 192.168.100.126
192.168.100.127 is broadcast address
192.168.100.129 - 192.168.100.190
192.168.100.191 is broadcast address
192.168.100.193 - 192.168.100.254
192.168.100.255 is broadcast address
If you choose to split the Class C 192.168.100.0/24 network up into four smaller /26 networks, you would get the subnets above. Obviously you would not longer be able to use 192.168.100.0 as a /24.
/24 is just the 'default' subnet mask for Class C addresses but you can make a subnet smaller or bigger by changing the subnet mask. Using a /26 is making it smaller and allowing you to have four smaller subnets instead of one larger /24 subnet.
Hopefully that makes some sense...