From: Hobbs (deadheadblues@gmail.com)
Date: Wed Feb 11 2009 - 22:01:56 ARST
I think I figured it out. This only works for directly connected
neighbors. When I use the distance command for 2.2.2.2, nothing
happens. It's still weird that it would affect LSAs that are not
generated by the router though...I guess it applies the distance to
all routes learned by that router.
Another example:
192.168.61.0 is between R1 and R6.
R4 learns this route through R5 right now and has a distance of 100:
R4#sho ip route 192.168.61.0
Routing entry for 192.168.61.0/24
Known via "ospf 1", distance 100, metric 3, type inter area
Last update from 192.168.45.5 on Serial1/0, 00:03:26 ago
Routing Descriptor Blocks:
* 192.168.45.5, from 5.5.5.5, 00:03:26 ago, via Serial1/0
Route metric is 3, traffic share count is 1
By manipulating cost I can have R4 choose the path through R3:
R5(config)#int s1/0
R5(config-if)#ip ospf cost 10
Now the LSA that is actually used to build the route entry is from R2,
and the distance command is not applied anymore (even though R2 ends
up using R5 as transit/load balancing))
R4#sho ip route 192.168.61.0
Routing entry for 192.168.61.0/24
Known via "ospf 1", distance 110, metric 4, type inter area
Last update from 192.168.34.3 on Serial1/1, 00:01:10 ago
Routing Descriptor Blocks:
* 192.168.45.5, from 5.5.5.5, 00:01:11 ago, via Serial1/0
Route metric is 4, traffic share count is 1
192.168.34.3, from 2.2.2.2, 00:01:11 ago, via Serial1/1
Route metric is 4, traffic share count is 1
Kind of interesting, it looks like OSPF uses one LSA to install the
route, but if multiple paths exists, i will install both paths.
However the distance command works on the LSA that was
installed...maybe not the correct way to explain it, still a little
fuzzy...
On Wed, Feb 11, 2009 at 4:51 PM, Hobbs <deadheadblues@gmail.com> wrote:
> Here you go:
>
> R4#sho ip route 1.1.1.1
> Routing entry for 1.1.1.1/32
> Known via "ospf 1", distance 100, metric 4, type inter area
> Last update from 192.168.45.5 on Serial1/0, 00:00:08 ago
> Routing Descriptor Blocks:
> 192.168.45.5, from 5.5.5.5, 00:00:08 ago, via Serial1/0
> Route metric is 4, traffic share count is 1
> * 192.168.34.3, from 2.2.2.2, 00:00:08 ago, via Serial1/1
> Route metric is 4, traffic share count is 1
>
> Here is a drawing of my topology
> http://imagebin.ca/view/st0dcn6.html
>
> thanks,
>
> On Wed, Feb 11, 2009 at 4:38 PM, Brian McGahan
> <bmcgahan@internetworkexpert.com> wrote:
>> Post the output of "show ip route 1.1.1.1".
>>
>> Brian McGahan, CCIE #8593 (R&S/SP/Security)
>> bmcgahan@internetworkexpert.com
>>
>> Internetwork Expert, Inc.
>> http://www.InternetworkExpert.com
>> Toll Free: 877-224-8987 x 705
>> Outside US: 775-826-4344 x 705
>>
>>
>>
>> Hobbs wrote:
>>
>> I have R4 as an internal router to Area 1.
>> R2 and R5 are border routers generating a type-3 LSA for route 1.1.1.1
>> into area 1.
>> Instead of using cost, I would like to use distance (if possible) to
>> alter path selection.
>>
>> R4 has two routes to 1.1.1.1
>> :
>>
>> R4#sho ip route | sec 1.1.1.1
>> O IA 1.1.1.1 [110/4] via 192.168.45.5, 00:01:10, Serial1/0
>> [110/4] via 192.168.34.3, 00:01:10, Serial1/1
>> R4#
>>
>> Here we see both type-3 LSAs, one each generated by R2 and R5:
>>
>> R4#sho ip osp database
>>
>> Summary Net Link States (Area 1)
>>
>> Link ID ADV Router Age Seq# Checksum
>> 1.1.1.1 2.2.2.2 207 0x80000001 0x0033FB
>> 1.1.1.1 5.5.5.5 170 0x80000002 0x00E040
>>
>>
>> R4(config)#router ospf 1
>> R4(config-router)#distance 100 5.5.5.5 0.0.0.0
>>
>> Both routes get changed:
>>
>> R4#sho ip route | sec 1.1.1.1
>> O IA 1.1.1.1 [100/4] via 192.168.45.5, 00:00:03, Serial1/0
>> [100/4] via 192.168.34.3, 00:00:03, Serial1/1
>>
>>
>> Why does the command alter both routes AD if I specified wildcard mask
>> of 0.0.0.0 ?
>>
>> I know that the ACL portion of the command works, to alter distance of
>> specific routes, but it appears the router-id/mask has no impact in
>> choosing between different ABR's.
>>
>> thank you,
>>
>>
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