summarization

[weasleman]

Hello

Trying to figure out summarization. Now i have my core router in a ring they are running 10.1.10.x 255.255.255.248. Now my networks are running 192.168.x.x

now first branch off my router holds the following networks

Network 1

192.168.98.0 255.255.255.0 Vlan MGMT1

192.168.150.0 255.255.255.0 Vlan 150

192.168.160.0 255.255.255.0 Vlan 160

192.168.170.0 255.255.255.0 Vlan 170

my second

Network2

192.168.99.0 Vlan MGMT2

192.168.100.0 255.255.255.0 Vlan  100

192.168.105.0 255.255.255.0 Vlan 105

192.168.110.0 255.255.255.0 Vlan 110

Router configuration

Network 10.1.10.0 0.0.0.7

network 10.1.10.8 0.0.0.7

Network 10.1.10.16 0.0.0.7

Ect.

Now how would i summarise the IP address in the various branches.

I have broken then down into Binary

                               128    64    32    16    8    4    2    1
                               
192.168.98.0/24       0    1    1    0    0    0    1    0
192.168.150.0/24     1    0    0    1    0    1    1    0
192.168.160.0/24     1    0    1    0    0    0    0    0
192.168.170.0/24     1    0    1    0    1    0    1    0

I am thinking with this configuration you would not be able to summarize the following. Only if the network is contigious?

[deanwebb]

Hello and welcome!

Route summarization is based upon which router interface is used to reach a particular network. Therefore, we need to know which interfaces are associated with which routes.

If, for example, your "Network 1" and "Network 2" were both routed via the same interface on the router, then they would all be able to be summarized with 192.168.0.0/16.

If, however, Network 1 goes with interface Gi0/1 and Network 2 goes with interface Gi0/2, then we can still summarize, but we must follow the rules of subnet masks. As long as the mask used on the route covers all the networks for the route and does not cover a network not in the route, it is OK to use.

So, if Net 1 and Net 2 are reachable via different interfaces, I see 3 networks on Network 1 that could be summarized and 2 networks on Network 2 that could be summarized.

[icecream-guy]

Summarization is moving the the mask bits to the left for a group of networks for advertisement.

192.168.0.0 /24
192.168.3.0 /24

i can move the mask bits to the left to create a summary route

192.168.0.0/22

this would include networks

192.168.0.0 /24
192.168.1.0 /24
192.168.2.0 /24
192.168.3.0 /24

btw i'm not talking about changing the masks on the interfaces, this would make them on the same network

[weasleman]

Hello,

I have a ring of 6 routers R1,R2,R3,R4,R5,R6 network1 is hanging off R1 and Network2 is hanging off R4.

So basically core is running on 10.1.10.x 255.255.255.248 but the access layer is running on the 192.168.x.x



                               128    64    32    16    8    4    2    1
                               
192.168.98.0/24       0    1    1    0    0    0    1    0
192.168.150.0/24     1    0    0    1    0    1    1    0
192.168.160.0/24     1    0    1    0    0    0    0    0
192.168.170.0/24     1    0    1    0    1    0    1    0

i would like to know how we got 192.168.0.0/22 though as from my understanding that you count the zeros from the left till you find mixed bits.

Thanks for the reply i really appreciate the help.

[deanwebb]

The thing to consider is what range the subnets exist in. 10.0.0.0 and 10.0.1.0 are in 10.0.0.0 /23. Making that a /22 would cover 10.0.0.0, 10.0.1.0, 10.0.2.0, and 10.0.3.0.

[weasleman]

I get you working out the bits for the 10.1.100.x

how would that work for the 192.168.x.x i have two networks seperated across routers.

With a mismash of IP address look at the ranges.

Network 1

192.168.98.0 255.255.255.0 Vlan MGMT1

192.168.150.0 255.255.255.0 Vlan 150

192.168.160.0 255.255.255.0 Vlan 160

192.168.170.0 255.255.255.0 Vlan 170

Network 2

192.168.99.0 Vlan MGMT2

192.168.100.0 255.255.255.0 Vlan  100

192.168.105.0 255.255.255.0 Vlan 105

192.168.110.0 255.255.255.0 Vlan 110

Network2

if we summarised would routing not get confused eg.

Network1 holds 192.168.98.x

3 routers between

network2 holds 192.168.99.x

I think i maybe confusing myself here but my brains saying in this scenario it would not be possible to sumerize without causing routing issues.

Thanks again for the help it is appreciated.

[deanwebb]

You're right that you can't sum *all* the routes for each Network. But you can have some of the routes left unsummarized and then summarize the routes that don't conflict with the others.

In Network 1, for example, 192.168.98.0 is not a good candidate for summarization because of 192.168.99.0 in Network 2. But the other three networks in Network 1 are all good candidates to be summed up in 192.168.128.0 /17.

[weasleman]

Thanks for clarifying so in this situation you would summarise the ones you can into one the ones that you couldnt you would just leave. Thanks again for getting back to me i was confusing myself for a minute.

Cheers

[deanwebb]

Thanks for clarifying so in this situation you would summarise the ones you can into one the ones that you couldnt you would just leave. Thanks again for getting back to me i was confusing myself for a minute.

Cheers

Exactly. Summarize what you can, when you can. The rest are left as is.

[icecream-guy]

Thanks for clarifying so in this situation you would summarise the ones you can into one the ones that you couldnt you would just leave. Thanks again for getting back to me i was confusing myself for a minute.

Cheers

Exactly. Summarize what you can, when you can. The rest are left as is.

That is why careful IP planning is most important.   you could always re-ip some of those subnets so that they play nice.

[weasleman]

I agree about planning but i find in the industry now that planning is not really the done thing. I have walked into many a company and had to try to fingure out why something was done a certain way to find no logic in the way things have been deployed.

I hate going round the house when i can walk directly there. Keep things simple.

[deanwebb]

I agree about planning but i find in the industry now that planning is not really the done thing.

Sad, but true... it's why we have facepalm icons...

[weasleman]

I wish i had that but i have this tourettes reflex.... funnily enough it only seems to manifest itself when im with idiots. You know the ones look at me im awesome i saved the day when really it was really someone else (the quiet guy that sits in the corner). Just a shame that in my last few roles we didnt have the quiet guy. They seem to be dying off....But the gob shi$es seem to be promoted to a management level. In the old days shit sank now it seems to rise to the surface. think maybe too much fibre (hot air)

I think someone need to have a book something like "Gob Shi$e for dummies".