[j-nsp] AS_PATH regular expression question.

[Vladimir S. Blazhkun]

> On 10/7/05, Vladimir S. Blazhkun <v.blazhkun at pcs-net.net> wrote:
>>
>> True or False: The regular expression of: 64512 .+ matches an AS path of
>> 64521 64567 65000?
>
> .+ = one or more instance of "." (any AS).

Sure, i know.

>> Theory ( JNCIS study guide by Joseph M. Soricelli ) says: false.
>>
>
> Can you be more specific (page number).

Page 68, question number 9. See answer and you will be surprised:

...The second AS in the path may be repeated further, but a new AS
number is not allowed...

>> Practice ( my Juniper M5 based network ) says: true.
>>
>> test at lab> show route aspath-regex "64512 .+" terse
>> Restart Complete
>> + = Active Route, - = Last Active, * = Both
>>
>> A Destination        P Prf   Metric 1   Metric 2  Next hop        AS path
>>    3.0.0.0/8          B 170        100        210 >10.186.0.125   64512 702 703 80 I
>>    6.5.0.0/19         B 170        100        210 >10.186.0.125   64512 702 702 702 702 I
>>
>> As you see it matches AS_PATH "64512 702 703 80", and not only "64512 702 702 702 702".
>>
>> What is the right answer you think?

-- 
Vladimir S. Blazhkun,
Lead IP NCC Specialist, JNCIA #773, OOO "PCS-Moscow",
Work phone: +7 095 7847617.