Hi All,
This task requires that "Cat2 will always prefer OSPF routes from R5"
"without using the 'bandwidth' or 'ip ospf cost' commands."
____
| |
R5 R6
|___|
|
CAT2
The DSG uses the distance command to reduce R5 sourced routes to AD109.
But as I understand, the 'distance' command cannot be used to select routes
within the same routing protocol as OSPF makes the SPF decision THEN moves
the route/s to the RIB. AD is then compared with other routing protocols or
checked for infinite value 255.
My testing shows that while the admin distance can be modified, both routes
still remain in the RIB as equal paths. The AD of the router that sourced
the route will be used for both equal path routes.
Additionally, depending on who originated the last route update, the route
source could be either R5 or R6.
Below thread shows a similar issue but the question remains, given
the constraints of the task and without actually filtering R6 routes or
giving them a 255 admin distance, is it possible to prefer the routes from
R5?
Thanks
James
*Roger RPF* rpf at bluemail.ch
<ccie_rs%40onlinestudylist.com?Subject=Re%3A%20%5BOSL%20%7C%20CCIE_RS%5D%20Viol%202%20Section13%20Task%206.3%20OSPF%20distance&In-Reply-To=%3C001a01c9733e%24a9586940%24fc093bc0%24%40ch%3E>
*Sat Jan 10 11:15:27 EST 2009*
Hi Jared,
Thanks, I got it.
But the task says: "Cat2 will always prefer OSPF routes from R5"
I know I am very bad in reading between the lines, furthermore I'm not
native english, but how do I have to understand that? To me, this task means
that for all OSPF routes he learns from R5 and R6, he will prefer R5.
That's why I was confused...
regards
Roger
-----Ursprüngliche Nachricht-----
Von: Jared Scrivener [mailto:jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>]
Gesendet: Samstag, 10. Januar 2009 17:07
An: 'Roger RPF'; ccie_rs at onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
Betreff: RE: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
Roger,
What you've described is EXACTLY how it should work. Quoting you:
"To me, this means from what I have seen, that the command
distance 109 <router-id>
changes only the admin distance of the "local routes" of that particular
router with that router-id, not ALL routes we are getting from it."
This is the correct functionality. Remember that OSPF is a link-state
protocol so each router advertises certain networks in its Type-1 (or
Type-2) LSA's. What the distance command is doing is changing the distance
for R5's Type 1 and Type 2 LSA's here.
That is the expected behaviour.
Cheers,
Jared Scrivener CCIE3 #16983 (R&S, Security, SP), CISSP
Technical Instructor - IPexpert, Inc.
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
Mailto: jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
-----Original Message-----
From: Roger RPF [mailto:rpf at bluemail.ch
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>]
Sent: Saturday, 10 January 2009 5:51 AM
To: jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>; ccie_rs at
onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
Subject: AW: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
Hi Jared,
Well, I tried it, cleared also the OSPF process but it dit not really help.
Well, to be more specific, it made it worse than when I used the router-id,
at least, the "local R5" routes got the better distance:
O 136.10.5.5/32 [109/2] via 136.10.56.5, 1d03h, Vlan56
O 136.10.25.0/30 [109/65] via 136.10.56.5, 1d03h, Vlan56
O 136.10.100.5/32 [109/1] via 136.10.56.5, 1d03h, Vlan56
but when I change the distance using the interface address, no route gets
the better distance.
To me, this means from what I have seen, that the command
distance 109 <router-id>
changes only the admin distance of the "local routes" of that particular
router with that router-id, not ALL routes we are getting from it.
But I think that is not how it SHOULD work, isn't it? Any ideas??
regards
Roger
-----Ursprüngliche Nachricht-----
Von: Jared Scrivener [mailto:jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>]
Gesendet: Samstag, 10. Januar 2009 02:59
An: 'Roger RPF'; ccie_rs at onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
Betreff: RE: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
Would you mind humouring me and trying:
distance 109 136.10.56.5 0.0.0.0 2
The OSPF distance command is meant to match based on router-id of the
advertising router for the network. Yours *appears* to have matched by the
network address instead.
Let me know how that goes.
Cheers,
Jared Scrivener CCIE3 #16983 (R&S, Security, SP), CISSP
Technical Instructor - IPexpert, Inc.
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
Mailto: jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
-----Original Message-----
From: Roger RPF [mailto:rpf at bluemail.ch
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>]
Sent: Friday, 9 January 2009 2:19 AM
To: jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>; ccie_rs at
onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
Subject: AW: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
I cleared the OSPF process, but still the same issue...
Any other ideas?
-----Ursprüngliche Nachricht-----
Von: Jared Scrivener [mailto:jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>]
Gesendet: Freitag, 9. Januar 2009 00:18
An: 'Roger RPF'; ccie_rs at onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
Betreff: RE: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
Did you set the router-id for OSPF on R5 to 136.10.5.5? The OSPF distance
command should apply to the neighbor's router-id.
Presuming that is correct, do a "clear ip ospf *" and see if that helps.
Cheers,
Jared Scrivener CCIE3 #16983 (R&S, Security, SP), CISSP
Technical Instructor - IPexpert, Inc.
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
Mailto: jscrivener at ipexpert.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
-----Original Message-----
From: ccie_rs-bounces at onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>
[mailto:ccie_rs-bounces at onlinestudylist.com
<http://onlinestudylist.com/mailman/listinfo/ccie_rs>] On Behalf Of
Roger RPF
Sent: Thursday, 8 January 2009 4:21 PM
To: ccie_rs at onlinestudylist.com
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Subject: [OSL | CCIE_RS] Viol 2 Section13 Task 6.3 OSPF distance
Hi group,
I have a question regarding this task. One of them tells us that "Cat2 will
always prefer OSPF routes from R5"
the PG shows the solution
router ospf 1
distance 109 136.10.5.5 0.0.0.0 2
access-list 2
permit any
But with this I will not see all OSPF routes preferred to R5. If I check my
routing table (see partial output below), I only set this distance to the
loopback of R5 (136.10.5.5) itself but for example for the routes to
loopback of R4 (136.10.4.4) or R2 (136.10.2.2) or even the external RIP
network from R2 (136.10.1.0), I still see both path over R5 and R6 and no
one will be preferred through R5.
O 136.10.5.5/32 [109/2] via 136.10.56.5, 00:00:20, Vlan56
O 136.10.4.4/32 [110/130] via 136.10.56.6, 00:00:20, Vlan56
[110/130] via 136.10.56.5, 00:00:20, Vlan56
O 136.10.2.2/32 [110/66] via 136.10.56.6, 00:00:20, Vlan56
[110/66] via 136.10.56.5, 00:00:20, Vlan56
O E2 136.10.1.0/24 [110/20] via 136.10.56.6, 00:00:20, Vlan56
[110/20] via 136.10.56.5, 00:00:21, Vlan56
Do I understand something wrong??
regards
Roger
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