From: Gustavo Novais (gustavo.novais@novabase.pt)
Date: Sun Dec 18 2005 - 14:05:36 GMT-3
Hi
No problem at all, I think that if on the lab I'll ask the proctor (I
think that for this one I'll know how to ask it).
My source is, as all my latest posts, IEWB version 3.0. This time it is
lab 15 question 4.8.
If you take it to the letter, you aren't changing the metric, but the
route-type, and just for sake of discussion, my preferred routes E1 have
metric 84 and my "not preferred" have metric 20 (default).
So, the metric does not play any role here... just the fact that OSPF
prefers E1 to E2.
I keep posting these problems here only because the solutions guide for
the labs I'm doing are yet to come out. And I need to have some kind of
feedback if my solutions are anywhere near the right one. Lab day is
getting near...
But sometimes the Brian's word could be useful in interpreting stuff.
Thanks you
Gustavo Novais
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Sean C.
Sent: domingo, 18 de Dezembro de 2005 19:39
To: Cisco certification
Subject: Re: set metric on route-map applied to OSPF distribute-list
route-map XXXX in
Hi Gustavo,
Interesting scenario - and solution. Good head scratcher!
I know you had basically solved the question and closed the post but
your
one comment made me curious - "but there's always the doubt of "is
setting
route-type considered changing metric"". My first instinct made me
think
'No, they're different', but I wanted to validate.
Searching the RFC 2328, I found this:
"OSPF supports two types of external metrics. Type 1 external metrics
are
expressed in the same units as OSPF interface cost (i.e., in terms of
the
link state metric). Type 2 external metrics are an order of magnitude
larger; any Type 2 metric is considered greater than the cost of any
path
internal to the AS."
This doesn't help at all! Arrghh! The way I read the statements, it
almost
does seem like it considers route-type to be synonymous as metric. I
did a
search on "route type" but nada there also. And..., I couldn't find
anything definitive in Doyle either.
I'd love to hear the opinion of Howard Berkowitz or one of the other
esteemed elders on this one. But, you're right, no matter what the
correct
answer is deemed to be, the question has to be read through the prism of
the
person that wrote the question (assuming this came from a 3rd-party
workbook - I couldn't find if you cite the source).
Again, interesting question and I was hoping to run with some CISSP
stuff
today but you got me thinking! Sorry for not finding an answer.
Sean
----- Original Message -----
From: "Gustavo Novais" <gustavo.novais@novabase.pt>
To: "Schulz, Dave" <DSchulz@dpsciences.com>; <nobody@groupstudy.com>;
"Josef
A " <josefnet@gmail.com>
Cc: "Cisco certification " <ccielab@groupstudy.com>
Sent: Sunday, December 18, 2005 7:28 AM
Subject: RE: set metric on route-map applied to OSPF distribute-list
route-map XXXX in
Hello Dave,
Thank you for your reply.
I'm aware of the distance command and of its possibilities. What I had
in
mind
was setting a distance or metric based on a TAG previously given to a
route.
For what I could see, distribute-list only allows you to permit or deny
a
route into route table, according to whatever attribute you specify on a
route-map. Distance only allows you to do that if you match the source
and
the
access-list.
I solved things a bit differently... on the preferred source
redistribution
points I redistributed tagged routes as E1 and all else as E2... It did
what
expected, but there's always the doubt of "is setting route-type
considered
changing metric?"
BTW, on the example you gave the source is matched by a wildcard mask
0.0.0.0,
not a 255.255.255.255. If you try entering that you'll be setting the
distance
for all sources the send you the route specified on the ACL.
Thank everybody for your inputs
Gustavo Novais
From: Schulz, Dave [mailto:DSchulz@dpsciences.com]
Sent: sabado, 17 de Dezembro de 2005 23:50
To: Gustavo Novais; nobody@groupstudy.com; Josef A
Cc: Cisco certification
Subject: RE: set metric on route-map applied to OSPF distribute-list
route-map
XXXX in
The Doyle tcp/ip book shows a number of examples that may help here
where
you
change the administrative distance on route or group of routes based on
where
it is coming from. For example.....
interface Ethernet0
ip address 10.1.1.1 255.255.255.0
!
!
router ospf 1
log-adjacency-changes
network 10.1.1.0 0.0.0.255 area 0
distance 100 2.2.2.2 255.255.255.255 2
!
access-list 2 permit 120.1.2.2
The distance is set a specific route (access-list 2) from a specific
source
(in ospf, this is the router-id of the remote router).
Hope this helps to think through your solution.
Dave
-----Original Message-----
From: nobody@groupstudy.com
To: Josef A
Cc: Cisco certification
Sent: 12/17/2005 2:56 PM
Subject: RE: set metric on route-map applied to OSPF distribute-list
route-map XXXX in
I just wanted to make a nice and versatile solution... not change costs
and
match specific routes... but...
If it is necessary...
Gustavo Novais
________________________________
From: Josef A [mailto:josefnet@gmail.com]
Sent: sabado, 17 de Dezembro de 2005 19:53
To: Gustavo Novais
Cc: Cisco certification
Subject: Re: set metric on route-map applied to OSPF distribute-list
route-map
XXXX in
Hello,
Try matching on the input interface instead of the next-hop.
Remember also that the router still computes the routes from the LSAs
which
are not filtered, and cost is an LSA attribute.
So this might(?) not be possible using a distribute-list.
Just a thought.
Thanks
Josef.
On 12/17/05, Gustavo Novais <gustavo.novais@novabase.pt> wrote:
Hello
I'm trying to make OSPF decide between two paths without changing any
interface values.
The same routes are coming from both paths(two different interfaces),
but only the ones tagged with 10 are to be decided upon one interface or
the other. When one path is not available, the other path should kick
in.
To do this I'm trying to build a route-map like this.
router ospf 1
router-id 150.1.5.5
distribute-list route-map AS10-PREFER in
route-map AS10-PREFER permit 10
match ip next-hop R4
match tag 10
set metric 20
!
route-map AS10-PREFER permit 20
match ip next-hop R3
match tag 10
set metric 30
!
route-map AS10-PREFER permit 30
This, theoretically would allow me to enter on the RIB the routes with
smaller metric.
The problem is that OSPF keeps ignoring my set statements and keeps the
routes always with metric 20, thus allowing load sharing to the tagged
paths.
The target routes are E2, but shouldn't the route-map act upon their
metric nonetheless?
Or because I'm using the route-map on a distribute-list the set commands
are not valid?
TIA
Gustavo Novais
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