CCNP route Struggles

MrXpert

I think i'm really stuggling with the CCNP route especially some of the stuff a lot of folk find easy. It all seems such a step up from CCNA.

I was wondering though if someone could help me with this problem on prefix lists

for example if the prefix 192.168.48.0/22 is denied then what block of addresses are denied as a result?

And stepping it up a little what would be denied if 192.168.48.0/22 le 24 were used instead? and why?

My subnetting skills are very good and I can subnet in my head within 10-15 seconds but for some reason i am struggling with prefixes.

Thanks

lordy

for example if the prefix 192.168.48.0/22 is denied then what block of addresses are denied as a result?

192.168.48.0 through 192.168.51.255.

I usually do this by counting from /24. /23 are two /24, /22 are four /24, /21 are eight /24 and so on. I never do any binary translation.

MrXpert

lordy wrote: »

192.168.48.0 through 192.168.51.255.

I usually do this by counting from /24. /23 are two /24, /22 are four /24, /21 are eight /24 and so on. I never do any binary translation.

i see I think I kinda....get it.

so for example permit 10.0.0.1/17 le 24 would mean 10.0.0.1 to 10.0.127.255? but the subnet mask must be /24 or higher?


and 172.16.0.0/23 ge 18 would be 172.16.0.1 to 172.16.1.255 but must have a /18 or higher. Anything less than a /18 even if it matched the range would still be denied?

okplaya

Which study materials are you using? I started out with the recommended FLG text but I could not get past chapter 2 to save my life. I decided to buy CCNP ROUTE Simplified (kindle version) and Chris Bryant ebooks/videos and I'm currently halfway through BGP. I'm sure I'll have to review, but it's progress nonetheless. If you are finding that you're having a tough time comprehending the concepts then I'd suggest investing in different study material. In my case it made a world of difference and have kept me motivated.

prtech

MrXpert wrote: »

i see I think I kinda....get it.

so for example permit 10.0.0.1/17 le 24 would mean 10.0.0.1 to 10.0.127.255? but the subnet mask must be /24 or higher?

No, le means less than or equal to so the subnet mask must be less than or equal to /24.

and 172.16.0.0/23 ge 18 would be 172.16.0.1 to 172.16.1.255 but must have a /18 or higher. Anything less than a /18 even if it matched the range would still be denied?

Exactly.

MrXpert

prtech wrote: »

No, le means less than or equal to so the subnet mask must be less than or equal to /24.
Exactly.

cheers! glad you spotted that. I have this habit of getting things arse about face.

MrXpert

okplaya wrote: »

Which study materials are you using? I started out with the recommended FLG text but I could not get past chapter 2 to save my life. I decided to buy CCNP ROUTE Simplified (kindle version) and Chris Bryant ebooks/videos and I'm currently halfway through BGP. I'm sure I'll have to review, but it's progress nonetheless. If you are finding that you're having a tough time comprehending the concepts then I'd suggest investing in different study material. In my case it made a world of difference and have kept me motivated.

I have the Chris Bryant videos and ebook and have watched CBT nuggets. I don't blame the material. Material seems good so far. I haven't used the FLG or OCG mainly because it looks kinda sleep inducing and i managed to pass my previous exams staying away from it, It's really down to me not understanding it. At least now i have a better idea of how it works so its best i just do some practice with it.

mattau

hang in there, route is a massive battle for sure. When I was first learning prefix lists I found it easier to treat the 2 parts as seperate. eg.
write your initial prefix down that is in your criteria to be matched
10.0.0.0/8 - then imagining that whole range of ip addresses to be available
you can then get more specific inside that whole range with the exact subnet masks but using ge le etc.

I think INE had a in depth PDF on alot of prefix list stuff with a few scenerios

Nate--IRL--

I found interpreting and writing down a few examples of Prefix lists in plain English will quickly cement the concept in your head.

This is especially important when you get to Distribute lists and re-distribution. Interpreting the syntax there is tricky to say the least.

Nate