supernetting

tell me if I'm right, say you got one ip address your suppose to super net. You are suppose to give out addresses from largest network to smallest network(router to router generally) correct? lets keep it simple and use typical class C 192.168.0.0 1st network 64 computers range .2-62(63 bc of course) router/default gateway f0/0 is .1 subnet mask is a /26 2nd network is 32 computers range .66 - .94(95 bc) r/d f0/0 is .65 mask is /27 3rd network is 16 computers range 96 - 110(111 bc) r/d f0/0 is .95 mask is /28 4th network is 8 computers range 122 - 126 (127 bc) r/d f0/0 is 121 mask is /29 ok lets say this is frame relay(haven't studied that yet but kinda know what it is kinda, let me know if that screws things up) and all the routers are connected to one central router so thats 4 /30 networks so the 1st is .29 -.30 second is 33-34 third is 31-32 then 35-36 between the central routers and the routers connected to the above network. So basecly I'm asking do I have this right? and is there a "best practice" so which of the /30s connect to which router or doesn't it matter?

Find more posts tagged with

Save $250 on 2025 certification boot camps from Infosec!

Book now with code EOY2025

Button

Comments

georgemc

jjbrog wrote: »

tell me if I'm right, say you got one ip address your suppose to super net. You are suppose to give out addresses from largest network to smallest network(router to router generally) correct? lets keep it simple and use typical class C 192.168.0.0 1st network 64 computers range .2-62(63 bc of course) router/default gateway f0/0 is .1 subnet mask is a /26 2nd network is 32 computers range .66 - .94(95 bc) r/d f0/0 is .65 mask is /27 3rd network is 16 computers range 96 - 110(111 bc) r/d f0/0 is .95 mask is /28 4th network is 8 computers range 122 - 126 (127 bc) r/d f0/0 is 121 mask is /29 ok lets say this is frame relay(haven't studied that yet but kinda know what it is kinda, let me know if that screws things up) and all the routers are connected to one central router so thats 4 /30 networks so the 1st is .29 -.30 second is 33-34 third is 31-32 then 35-36 between the central routers and the routers connected to the above network. So basecly I'm asking do I have this right? and is there a "best practice" so which of the /30s connect to which router or doesn't it matter?

Uuhhh....

That has nothing to do with supernetting. What you're doing there is called variable length subnet masking (VLSM). I tend to put the larger subnets(/25), /26) at the low end of the range and the smaller subnets (/29, /30) at the high end of the range.

Supernetting is where you take multiple contiguous Class Cs, etc. and combine them together to have a single summarized/aggregated network/route that you can advertise.

I.E. I can summarize the class C network 192.168.0.0, 192.168.1.0, 192.168.2.0, and 192.168.3.0 /24 into a summarized route/network of 192.168.0.0 /22.

M4verick

jjbrog wrote:

tell me if I'm right, say you got one ip address your suppose to super net. You are suppose to give out addresses from largest network to smallest network(router to router generally) correct? lets keep it simple and use typical class C 192.168.0.0

1st network 64 computers range .2-62(63 bc of course) router/default gateway f0/0 is .1 subnet mask is a /26
2nd network is 32 computers range .66 - .94(95 bc) r/d f0/0 is .65 mask is /27
3rd network is 16 computers range 96 - 110(111 bc) r/d f0/0 is .95 mask is /28
4th network is 8 computers range 122 - 126 (127 bc) r/d f0/0 is 121 mask is /29

ok lets say this is frame relay(haven't studied that yet but kinda know what it is kinda, let me know if that screws things up) and all the routers are connected to one central router
so thats 4 /30 networks so the 1st is .29 -.30 second is 33-34 third is 31-32 then 35-36 between the central routers and the routers connected to the above network.

So basecly I'm asking do I have this right? and is there a "best practice" so which of the /30s connect to which router or doesn't it matter?

Hey buddy. That's a mess to read.

Mebbe just try to lay it out so it's easier on the eyes in the future. I did it for you to try and make it easier for others to read your question. Also, yeah, georgemc already said it, but this is VLSM.

Either way, to attempt at answering your question. I'm fixing your 4th network because is looks like you inadvertantly solved for 120 instead of 112 and skipped that little range, so that should have been 112 - 119.
I'm going to retype a portion of what you did for clarification (ignoring your rule for using the first IP as the default gateway.)

For everyone else new to subnetting, remember that the first IP is unuseable as it is the network ID, and the last one is unuseable as it's reserved for broadcast.
Class C - 192.168.0.0/24
1) 192.168.0.0/26 = 192.168.0.0 - 192.168.0.63
2) 192.168.0.64/27 = 192.168.0.64 - 192.168.0.95
3) 192.168.0.96/28 = 192.168.0.96 - 192.168.0.111
4) 192.168.0.112/29 = 192.168.0.112 - 192.168.0.119

Ok, now, fixing your /30 networks -
A) 192.168.0.120/30 = 192.168.0.120 - 192.168.0.123

192.168.0.124/30 = 192.168.0.124 - 192.168.0.127
C) 192.168.0.128/30 = 192.168.0.128 - 192.168.0.131
D) 192.168.0.132/30 = 192.168.0.132 - 192.168.0.135

Ok, general rule is that while it's not technically required, it is much easier to start off with the largest range and work your way down.

As far as best practices for implementing /30 networks, if I'm using serial connections I'll use the lower IP address for the DCE side that sets the clock rate. Just easier to remember in my mind. But it does also depend on your implementation of frame relay. That is a series of Point-to-point connections. You can get away with point-to-multipoint connection and just use one /29 range.

So, instead of using your four /30 networks, use one /29 and it'd look like this -
192.168.0.120/29 = 192.168.0.120 - 192.168.0.127

That gives you 6 useable IP addresses, so you could potentially add two more networks with that setup. Also, notice I saved more IP's by going that route.

jjbrog

oh yeah sorry got mixed up, i know about router summerization , but yeah so what I wrote will work for the most part?

jjbrog

Oh and thanks to you Maverick, I was kinda and still am half awake when I posted and totally made a mess. but yeah at first, wile using packet tracer I was startng with the small networks and working my way up, didn't work at all, and just had overlapping errors, and starting fromthe largest and working my way down. good plan for dce though, I think i'll try to do that myself from now on. I am in the cisco networking academy at my school and we got a subnetting lab next week which will probably be vlsm and doing basecly that

M4verick

jjbrog wrote: »

Oh and thanks to you Maverick, I was kinda and still am half awake when I posted and totally made a mess. but yeah at first, wile using packet tracer I was startng with the small networks and working my way up, didn't work at all, and just had overlapping errors, and starting fromthe largest and working my way down. good plan for dce though, I think i'll try to do that myself from now on. I am in the cisco networking academy at my school and we got a subnetting lab next week which will probably be vlsm and doing basecly that

Hey, no prob/worries. Good luck with your studies man.