Can I have more than one subnet on the same Network?

[monahan]

Im trying to squeeze 1100 nodes out the same two class C IP's

I need three LAN's on the same network
LAN 1
LAN 2
LAN 3

LAN's 1 and 2 have to be isolated
LAN 3 can talk to 1 or 2

I figure if I supernet the two with with class B subnet 255.255.254.0 and aggregate then for 510 nodes for LAN 1, then I can supernet the same two with another netmask of 255.255.252.0

Can this be done?

 

[dbcrossfire]

I'm not sure if your going to be able to get 510 nodes out of a class c ip addy, although I'm probably wrong. if you can, it's going to take a long time to figure out the table of ip address.

on a network that big, wouldn't it just be more efficient to take two routers and set up each one with one of your class c ip addys and then set the routers up for dhcp?

 

[L3Guy]

monahan;

If I understand you correctly: NO, it can't be done that way.

You are going to have to get enough addresses or fire up NAT.

Supernets with different subnets are not seen as unique, and one ore the other will get chosen.

Feel free tp PM me, or email me.

Regards;

Doug

 

[monahan]

L3guy,

I was afraid of that.

I couldn't figure out how more than one subnet could be on the same network, and I guess that's the reason why.
It can't be done. Only one is going to be accepted by the local router.
Maybe if I had two remote networks.

But then I would have to double up on all the equipement for the DMZ, firewall and stuff.

 

[L3Guy]

monahan;

To clarify, its not that supernetting will not work. You can combine 4 class C nets into a supernet.
Its that every address still has to be unique.

Example.
192.168.4.0 /24
192.168.5.0 /24
192.168.6.0 /24
192.168.7.0 /24
can be combined into:
192.168.4.0 /22 or 255.255.255.252

But if you also created a
192.168.6.0 /23 or 255.255.255.254
a router would assume you were addressing a part of 192.168.4.0, rather than a different block.
If a router had a route to both, it would always pick the more specific route, and the (non-unique) hosts in the other block would be unreachable.

Hope this helps;

Doug

 

[monahan]

Doug,

Again, thanks that does help.
I'm taking a network plus course and I've been struggling with this since I first heard about subnetting.

What you last posted re-enforced what I understood.
To meet the needs of the network I'm supposed to design, I could just do exactly what you posted - supernet 4 IP's together for 1022 nodes and run NAT or supernet 5 IP's and skip NAT and let everyone have their own IP constant IP address.

But I was trying to save on class c IP addresses.

Is there a way I could use more than one router to talk to the same firewall?
I was thinking on using a setup like the one presented here:
http://www.ssimail.com/Zoneguard.htm

 

[monahan]

Wait a minute,

I think I finally get it.

No matter how many netmasks I use, ALL the routers are going to think the packets are destined for the same network.

I guess I was trying to 'subnet' a supernet.

Apparantly, that can't be done

Oh well,

I'll just have to go with NAT then.

Thanks

 

[monahan]

By the way,

I emailed you my network design.

 

[Damaged]

<< 192.168.4.0 /22 or 255.255.255.252 >>


'cept that netmask is incorrect. It should be 255.255.252.0 255.255.255.252 is a /30. Same goes for the /23. That's actually 255.255.254.0

 

[L3Guy]

Damaged;

LOL.

I hate it when I do that in public!

Thanks for the catch.

Doug

 

[Damaged]

np. I knew what you meant though. And at least you had the proper equivalent, just in the wrong octect.

 

[JackBurton]

Dude, why do you HAVE to use class C IPs?