From: Leigh Harrison (ccileigh@gmail.com)
Date: Thu Nov 17 2005 - 07:01:00 GMT-3
Hey there fellas,
I understand where you're coming from (and I'm going to have to guess a
bit here - but it's an educated one)
If a metric in RIP hits 16 then it's classed as rubbish.
An offset list will add to the current metric (offsetting it from the
current vaule)
Your offset list (I'm guessing here) is adding enough to make the value
of the route 16, therefore making it rubbish. Your router needs to know
which routes to add the offset to (we'll call it 16 - just to make sure
it's rubbish). Your access-list in this instance is not dropping or
permitting active traffic, but it rather being used to select traffic
for use in the offset list.
So your acl is selecting the traffic that you want your offset list to
add 16 (or any other value to make it rubbish) and make the route(s)
unusable.
You want to only have odd routes. So you need to make the even routes
look rubbish. That's why they are selected by the acl, and filddled
with in the offset list, making the even routes rubbish and not
touching the odd routes so they will pop into the table just fine.
LH
John Matus wrote:
>ok,
>this has always gotten me and i still don't understand why
>lets say that you want to deny all routes (in rip) coming in w/ an even
>second octet. when i look @ IE's solution guide, they show an offset list
>with an ACL attached that is:
>
>access-list 1 permit 0.0.0.0 255.254.255.255 ( the stipulation
>is that the acl can only be 1 line), so this is supposed to say, i'm
>assuming "permit odd routes"
>
>but.....
>from my understanding, if you have a 0 in the octet you are trying to
>filter, then the octet is going to be even, and with a mask of 254, you are
>going to be matching the 1's column, so it would seem to me that:
>permit 0.0.0.0 255.254.255.255 would actually PERMIT all even routes
>rather than denying them (my solution to the problem was "permit 0.1.0.0
>255.254.255.255" which i believed would permit all odd routes...........but
>it seems that i am mistaken somehow........
>
>what am i not getting??
>
>
>Regards,
>
>John D. Matus
>Technical Support / PAS
>Fujitsu Consulting
>626-568-7716
>John.Matus@tokiom.com
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