IP Prefix-List error in the CCNP ROUTE OCG?

poguepogue Senior MemberMember Posts: 213
No one responded to the last question like this I asked.. Hopefully better luck this time.. I looked in the errata for this, but could not find anything.

Table 4-4, page 108 in the OCG says this prefix-list command parameter:

10.128.0.0/9

matches 2 of the following prefixes:

10.0.0.0/8
10.128.0.0/9
10.1.1.0/24
10.1.2.0/24
10.128.10.4/30
10.128.10.8/30

I only see 1 match. I labbed this, and tested both 10.0.0.0/8 and 10.128.0.0/9 with the following:


router eigrp 1
distribute-list prefix russ out

ip prefix-list russ seq 6 deny 10.128.0.0/9
ip prefix-list russ seq 10 permit 0.0.0.0/0 le 32

I changed a single network off Fa0/0 on this router between 10.0.0.1/8 and 10.128.0.1/9. 10.128.0.0 gets blocked in outgoing updates.. 10.0.0.0 does not.

This seems to me to be proper behavior, yet the book says this prefix-list should be hitting two networks.

Help? I KNOW prefix-lists are likely to be covered thoroughly in the exam, so I want to make sure this is an error in the book and not in my understanding.

Thanks,

Russ
Currently working on: CCNA:Security
Up next: CCNA:Voice

Comments

  • EildorEildor Senior Member Member Posts: 444
    pogue wrote: »
    No one responded to the last question like this I asked.. Hopefully better luck this time.. I looked in the errata for this, but could not find anything.

    Table 4-4, page 108 in the OCG says this prefix-list command parameter:

    10.128.0.0/9

    matches 2 of the following prefixes:

    10.0.0.0/8
    10.128.0.0/9
    10.1.1.0/24
    10.1.2.0/24
    10.128.10.4/30
    10.128.10.8/30

    I only see 1 match. I labbed this, and tested both 10.0.0.0/8 and 10.128.0.0/9 with the following:


    router eigrp 1
    distribute-list prefix russ out

    ip prefix-list russ seq 6 deny 10.128.0.0/9
    ip prefix-list russ seq 10 permit 0.0.0.0/0 le 32

    I changed a single network off Fa0/0 on this router between 10.0.0.1/8 and 10.128.0.1/9. 10.128.0.0 gets blocked in outgoing updates.. 10.0.0.0 does not.

    This seems to me to be proper behavior, yet the book says this prefix-list should be hitting two networks.

    Help? I KNOW prefix-lists are likely to be covered thoroughly in the exam, so I want to make sure this is an error in the book and not in my understanding.

    Thanks,

    Russ

    I think you might have misunderstood how the table is read. The 2 under "Routes Matched from previous list of prefixes" is referring to which of the routes were matched from the list on page 107. The 2 is not referring to the number of routes that were matched.

    I hope that makes sense.
  • jwashington1981jwashington1981 Senior Member Member Posts: 137
    I'm actually on the very same chapter. Eildor is correct. It's referring to route 2 from the previous page on page 107 (10.128.0.0/9).
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