From: Gary Bartlett (ciscokid@sympatico.ca)
Date: Fri Sep 12 2003 - 21:32:24 GMT-3
Hey guys,
Thanks for all of your responses, I liked your explanation Raj, it was
helpful.
But I still feel as though my answer for question 2 is correct
ip prefix-list test22 seq 5 permit 172.16.0.0/12 ge 16 le 32
It fits the requirements, I think a better way of looking at the
question is:
Match network 172.16.0.0/16 & it's subnets
Match network 172.17.0.0/16 & it's subnets
Match network 172.18.0.0/16 & it's subnets
...
...
Match network 172.31.0.0/16 & it's subnets
Therefore the 1st 12 bits must be matched, but only if the masks are in
the range of 16 to 32
P.S. Bin if you're reading this, I appreciate your insight, but I don't
think it is correct:
ip as-path access-list 12 permit ^698_
ip as-path access-list 13 permit _405_
your above suggestion would not meet thee requirements, because once it
matched the 1st statement, the second statement would not be considered.
Raj explained it best with the following:
^698_(.+_)*405_
Where it says received from AS698, match any number of AS in between
then match AS405 and then I don't care what else it passes through till
origin. I only care about received AS and pass through AS405.
Thanks,
Gary
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
McClure, Allen
Sent: Friday, September 12, 2003 11:56 AM
To: ccielab@groupstudy.com
Subject: RE: prefix & AS-path questions
PLEASE correct me if I'm wrong here:
ip prefix-list test22 seq 5 permit 172.16.0.0/12 ge 16 le 32 - Will
pass the 172.16.0.0/14 network correct? This will break the
requirement.
I'm inclined to belive that ip prefix-list test seq 5 permit
172.16.0.0/12 le 32 would catch masks /12-/32 and meet the requirement
correct?
Gary, you've already seen this from me, but I wanted to verify with the
group.
Allen G. McClure
CCNP/CCDP/MCSE
Yum! Brands, Inc.
Sr. Network Analyst
allen.mcclure@yum.com
-----Original Message-----
From: raj_tpd@comcast.net [mailto:raj_tpd@comcast.net]
Sent: Thursday, September 11, 2003 11:34 PM
To: Gary Bartlett
Cc: ccielab@groupstudy.com
Subject: Re: prefix & AS-path questions
Here is what I think.
For
1. sets the local pref to 400 for any paths learned directly from AS 698
that
pass through AS 405.
Answer i think: ip as-path access-list 12 permit ^698_(.+_)*405_
when you said ^698_(.+_)*405_(.+_)$ means received from AS698 pass
through any
number of AS then match 0 or more sequence of AS405 and then match again
any
number of AS till origin.
Why do it that way when there is a build in function.
^698_(.+_)*405_
Where it says received from AS698, match any number of AS in between
then match
AS405 and then I don't care what else it passes through till origin. I
only
care about received AS and pass through AS405. Leave the rest on the
program to
figure it out.
For
2. Sets the weight to 10,000 and the local preference to 60 for networks
in the
range 172.16.0.0/16 to 172.31.0.0/16 network, and any of their subnets.
Answer i think: ip prefix-list test22 seq 5 permit 172.16.0.0/12 ge 16
le 32
This is saying match first 12 bits exactly what I have said and then
from bit
16 to 32 I do not care.
I think the rest looks good.
I might be totally off, I that case please do correct me. I will learn a
thing
or two. Just my 2 cents.
Raj
> So it's coming down to the wire for me now, I'll be taking the exam on
> Sept 18th in RTP. There are still a few things I'm not comfortable
> with, so if you could help me with these I'd appreciate it. Thanks,
> Gary
>
> 1. Construct a route map that sets the BGP local preference to 200 for
> any paths learned directly from AS 307, sets the local pref to 400 for
> any paths learned directly from AS 698 that pass through AS 405, and
> denies all other paths.
> 2. Construct a route map that:
> - Sets the origin code to "incomplete" and the local preference to 50
> for the 10.0.0.0/8 network and any of its subnets.
> - Sets the weight to 10,000 and the local preference to 60 for
networks
> in the range 172.16.0.0/16 to 172.31.0.0/16 network, and any of their
> subnets.
> - Sets the local preference to 70 for any 192.168.x.0/24 network or
> subnet.
> - Denies all other prefixes.
>
> MY ANSWERS
> 1)
> route-map ex1 permit 10
> match as-path 11
> set local-preference 200
> route-map ex1 permit 20
> match as-path 12
> set local-preference 400
> ip as-path access-list 11 permit ^307_
> ip as-path access-list 12 permit ^698_(.+_)*405_(.+_)$
> -------------------------
>
> 2)
> route-map ex2 permit 10
> match ip address prefix test21
> set origine incomplete
> set local-preference 50
> route-map ex2 permit 20
> match ip address prefix test22
> set weight 10000
> set local-preference 60
> route-map ex2 permit 30
> match ip address prefix test23
> set local-preference 70
> ip prefix-list test21 seq 5 permit 10.0.0.0/8 le 32
> ip prefix-list test22 seq 5 permit 172.16.0.0/12 ge 16 le 32
> ----------------------
> ip prefix-list test23 seq 5 permit 192.168.0.0/16 le 32
>
> COMMENTS:
> 1) My problem is that they said passed through as 405, but they didn't
> say originated from AS 405, that's why my answer is different...
> 2) I added ge 16 because in the question they said that the 3rd octet
> could be any # in the range of 16 to 31, but the subnet would still be
> /16 to /32... THERE ANSWERS
> 1.
> route-map test1 permit 10
> match as-path 1
> set local preference 200
> route-map test1 permit 20
> match as-path 11
> set local preference 400
>
> ip as-path access-list 1 permit ^307_
> ip as-path access-list 11 permit ^698_(.+_)*405_ -----------------
> 2. route-map test2 permit 10
> match ip address prefix test2a
> set origin incomplete
> set local-preference 50
> route-map test2 permit 20
> match ip address prefix test2b
> set weight 10000
> set local-preference 60
> route-map test2 permit 30
> match ip address prefix test2c
> set local-preference 70
> ip prefix-list test2a seq 5 permit 10.0.0.0/8 le 32
> ip prefix-list test2b seq 5 permit 172.16.0.0/12 le 32
> ----------------
> ip prefix-list test2c seq 5 permit 192.168.0.0/16 le 32
>
>
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