Loopback on same network unreachable

[Michael_Goodlif]

Hi, I am trying to connect another switch to my network to segregate customer vlan's.

I am announcing my networks as /24's and want to create smaller subnets of these on another switch within my network. So for example create a loopback vlan with a /29 for a single client server connection.

I am testing this in my lab where I have a single network of 192.168.1.1/24. I have created a vlan "InputLB" which is set as loopback and has ipforwarding on. This vlan has 1 port which is active and is connected to the main 192.168.1.1/24 network. This InputLB vlan is assigned the IP address 192.168.1.33/29.

When I try to ping the 192.168.1.33 from any devie on my network, it will not ping. What am I doing wrong? Will this configuration be possible?

Thanks for any help.

[Michael_Goodlif]

For example I have 4 /24 subnets announced:

x.x.160.0/24
x.x.161.0/24
x.x.162.0/24
x.x.163.0/24

I want to take the 163 subnet and split it into multiple vlan's over different ports. For example take port 12 of my newly attached switch, make it a loopback interface and give it the network x.x.163.16/29

Do I need to change my announcements every time I want to create a new subnet? Or instead split them all up now and change the announcements so they match.

I have just tried removing the network of the 163.0/24 network on my router and creating it as 163.8/29 instead, however now the gateway of this new /29 is unreachable (x.x.163.9)

[Michael_Goodlif]

Thanks I see what you mean. I have my /24's announced over bgp at the moment. Does this mean that I must have the /24 vlan's defined on my switch which correspond to these /24 networks I am announcing?

What I want to do is have one of my /24 networks split into multiple /29, /28 networks for clients, but still be able to announce it as a single /24

Thanks.

[dflouret]

Michael,

Your configuration is invalid. You can summarize the advertisement of several subnets with a smaller mask (larger subnet), but the separate subnets must not overlap.

Using a /29 mask you can have 32 non overlaping subnets:

• 192.168.1.0/29
• 192.168.1.8/29
• 192.168.1.16/29
• 192.168.1.24/29
• .......
• 192.168.1.224/29
• 192.168.1.232/29
• 192.168.1.240/29
• 192.168.1.248/29

In your configuration subnets 192.168.1.0/24 and 192.168.1.32/29 overlap, which makes it impossible to determine if a computer using IP address 192.168.1.35 resides in the 192.168.1.0/24 subnet or in the 192.168.1.32/29 subnet.

What are you trying to accomplish with that?

Daniel

[Ronald_Dvorak]

I'm not sure whether I unterstand your setup so....
Your main network is 192.168.1.0/24 and now you've configured 192.168.1.33/29 on the switch,
If that is the case then this is not correct - you can't use different masks for the same range = 192.168.1.33 is included in the 192.168.1.0/24 range.
Might be helpful if you post a network diagram and the configuration.