Static Routing With Classless Subnets

sthompson86

Good morning - I am having some trouble here with a troubleshooting lab I was given.


What I am having trouble doing is statically routing classless networks.

In my efforts to try and figure this out I have a created a small test network with 3 routers linked via serial.

Router 1 has the following interfaces configured : S0/0 172.20.1.1 /26

Router 2 has the following interfaces configured : S0/0 172.20.1.2 /26
S0/1 192.168.38.254 /30

Router 3 has the following interfaces configured : S0/0 192.168.38.253 /30

( The routers can ping their directly connected counterpart thats on the same network just not the interface of the other networks)

I added the static routes with the correct address as shown above, and in the below example from Router1.

Router1#configure terminal
Router1(config)#
Router1(config)#ip route 192.168.38.0 255.255.255.252 172.20.1.2

________________________________________

I can configure a static route using /24 all day long with ease, but this is the first time I have done classes, and its not working. I also have only been studying CCENT, and I do not remember classless routing being a hot subject on any of the videos or books I watched and read.

Lastly, I did search the forums and Google before I made this thread, and I find stuff that somewhat concerns what I am trying to do, but I really am not getting anything out of what I am reading towards fixing my problem.

Thanks all in advanced.

okplaya

Can you post the "sh ip route static" from each router?

Are they connected like this...R1 -> R2 -> R3?

Thanks

Edit: Also, turn on "debug ip packet" while you're trying to ping to explore.

networker050184

sthompson86 wrote: »

Router1#configure terminal
Router1(config)#
Router1(config)#ip route 192.168.38.0 255.255.255.252 172.20.1.2

Where is the 192.168.38.0/30 subnet located? You show the routers being connected with 192.168.38.252/30. If you are trying to ping that you will need a route to that network. Also don't forget a route back is needed as well. Routing is two way. Just because Router1 can get to Router3 it doesn't mean Router3 knows how to get back.

sthompson86

okplaya wrote: »

Can you post the "sh ip route static" from each router?

Are they connected like this...R1 -> R2 -> R3?

Thanks

Edit: Also, turn on "debug ip packet" while you're trying to ping to explore.

Yes thats how they are connected. Below is the requested list.

Router1#show ip route static
192.168.38.0/30 is subnetted, 1 subnets
S 192.168.38.0 [1/0] via 172.20.1.2

Router2* I did not configure any static routes, for everything ties into it directly.

Router3#show ip route static
172.20.0.0/26 is subnetted, 1 subnets
S 172.20.1.0 [1/0] via 192.168.38.254

burbankmarc

192.168.38.0/30 is for hosts 192.168.38.1 and 192.168.38.2. 192.168.38.252/30 is for hosts 192.168.38.253 and 192.168.38.254.

sthompson86

I can post my Packet Tracer lab if that will help? right now yall are confusing me lol

networker050184

What are you trying to ping (and from what router) and what router is the destination connected to?

sthompson86

networker050184 wrote: »

What are you trying to ping (and from what router) and what router is the destination connected to?

I have a triangle of 3 routers.

I am trying to ping from router 1 to router 3 and visa versa.

I just do not understand what I am missing when it comes to classless routes. If I do took this same topology of 3 routers, and I made every network a /24 it would work no problem.

Thank you for trying to help me out.

networker050184

I think you have a misunderstanding of subnets.

ip route 192.168.38.0 255.255.255.252 = hosts 192.168.39.1 and 192.168.38.2

Yet, you have 192.168.38.252 255.255.255.252 assigned to your link. You have the wrong range routed.

sthompson86

Thats what I have done.. Makes sense now because I pulled all this from a lab that was broke on purpose.. and I guess that was one of the things I was supposed to "Fix"

Thanks everyone for your help!

sthompson86

Hate to bring this back up, but in my studies this morning I was struck with a Ripv2 setup in a lab.

I had to setup RipV2 for network 209.165.201.128 255.255.255.240

So i did what I thought was right and did

(config-Router)# Network 209.165.201.128

The network range .128 - .143

My routers interface using this network had an address of .142

________

Nonetheless when I reviewed the answers Show Run ( which I included the Rip portion of in the attached picture) it showed that I should have put the network as

209.165.201.0

Now .0 in my opinion has a range .0 - .15 No where near .142

The notes in the Show Run config stated " Remember that the Network command needs classfull network numbers, even though RIPv2 is a classless routing protocol."

Going back to my original post in this thread the above statement goes against everything I was told in this thread, for what the statement is telling is against everything I did to fix my original issue when I was trying classless RIP routing vs Classfull.


In my final preparations for the CCENT things like this that are completely different from what I have learned really throw me for a loop.

Thanks in advanced.

networker050184

RIP will change any network statement to the classful for automatically. The mask on the interface still determines what is advertised along with your auto summary config.

This is why passive interfaces and filtering are important in RIP.

sthompson86

networker050184 wrote: »

RIP will change any network statement to the classful for automatically. The mask on the interface still determines what is advertised along with your auto summary config.

This is why passive interfaces and filtering are important in RIP.

So was I right for putting the network as .128 instead of .0 ?

okplaya

sthompson86 wrote: »

So was I right for putting the network as .128 instead of .0 ?

For exam purposes you were wrong, but in real world the router will let you input it that way and change it (as networker stated). For example, if you put network 10.10.10.128, it will accept the command and change it to the classful network 10.0.0.0 in the config. That is the behavior of the protocol on a real router. On the exams, inputting it the "wrong" way could cost you as it may not work. That's why it is important to double check if you encounter such. The configuration doesn't lie.

As for the exam, don't sweat it man. You sound like you're more than prepared, and you'll do fine.

sthompson86

okplaya wrote: »

For exam purposes you were wrong, but in real world the router will let you input it that way and change it (as networker stated). For example, if you put network 10.10.10.128, it will accept the command and change it to the classful network 10.0.0.0 in the config. That is the behavior of the protocol on a real router. On the exams, inputting it the "wrong" way could cost you as it may not work. That's why it is important to double check if you encounter such. The configuration doesn't lie.

As for the exam, don't sweat it man. You sound like you're more than prepared, and you'll do fine.

Thank you, So on exams I need to stick with classfull even though that doesnt work in the real world well atleast on PT hince why I made this thread originally.

okplaya

If configuring RIP, I'd make it a habit to configure the classful network. If you want to see what I am talking about, in PT, configure RIP on a router and use 'network 10.10.10.128' command. Then go and do a "sh run" and see the network statement in the config.

HTH

sthompson86

okplaya wrote: »

If configuring RIP, I'd make it a habit to configure the classful network. If you want to see what I am talking about, in PT, configure RIP on a router and use 'network 10.10.10.128' command. Then go and do a "sh run" and see the network statement in the config.

HTH

You are saying that 10.10.10.128 will show up as 10.0.0.0 . But, I guess it will still route classess if I use RIPV2?

Really sorry for the back to back questions, but this really has me confused.

CodeBlox

In the running-config, RIP(v2) network statements are done at the classful boundary. RIPv2 however does allow subnet information to be sent. So, if you entered the network statement: "network 10.12.32.128" it would show up as "network 10.0.0.0" in both RIP and RIPv2. RIPv2 would however send subnet mask information and the classless route would be advertised.

sthompson86

I believe what I did that has me all confused was get static route entries confused with RIPV1/2 entries.

For when I setup a static route I always use the full on network address no 0's unless its the 0 subnet.

I am just so far into my CCENT studies that any differentiation in something that I think is correct realllly screws me up. If that makes any since.. lol

CodeBlox

You'll want to learn the basics correctly. In the routing table, static routes are denoted "S" while RIP(v2) routes are denoted "R"

Do a "show ip route" and see what I mean. In the routing table, the static route doesn't auto summarize like RIPv2 does by default.

sthompson86

CodeBlox wrote: »

In the routing table, the static route doesn't auto summarize like RIPv2 does by default.

Thats what had me confused. - Thanks all for helping me get this cleared up.