Re: Redistribution Problem

Vince,

Let's put it this way; from the local router's point of view is there any
way to make those routes look like 2 suggestions from the "same" routing
protocol?

HTH

Kambiz Agahian

CCIE Instructor/Consultant
M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA

On Sat, Aug 28, 2010 at 12:55 AM, Vince Librandi <vlibrandi_at_internode.on.net
> wrote:

>
>
> I was always under the impression that it was first in would stay in (until
> withdrawn) when it came two routing processes with the same AD. But at least
> this way it gives you a predicatable behaviour you can work with.
>
> If the man with the expensive tie really wanted it 3 ways you could solve
> it would be:
>
> Split the network to be load balanced in half. Then on R5 set the AD for
> one 1/2 down in one AS and the other down in the other. Not true load
> balancing and it wouldn't work with /32.
>
> 2x GRE tunnels. One via R3-R5 and the other via R4-R5 then extend out the
> OSPF domain to R5. Then tweak the metrics to get the network to load balance
> on R5.
>
> MPLS TE. set up 2 paths one via R5 - R3 - R2 - R1 and the other R5 - R4 -
> R1
>
> Are there any others that I have missed (or an easier one)?
>
>
> Question for the group, when you have 2 OSPF routing processes with the
> same prefix is it the lowest process ID that gets chosen? Just wondering if
> this is common across the protocols now.
>
> Vince
>
>
>
>
> On 28/08/2010 8:28 AM, Kambiz Agahian wrote:
>
>> Hemanth,
>>
>> Now the million dollar question is how to enable load balancing in
>> scenarios
>> like this ? :) ... we can think of several ways.
>>
>> PS. Just to make sure everyone's clear on the last point and everybody's
>> on
>> the same page, in this case since we're learning the routes from two
>> different AS's (AS - Autonomous System - just think about
>> it...."autonomous" what does it mean?) both ways of route selection (prior
>> to 12.2 and beyond that) make perfect sense. And the LB option is not such
>> a
>> great idea.
>>
>> In a normal situation however you probably don't want to load balance
>> across
>> two different networks (i.e. different management, routing policies, fees,
>> SLA's etc.).
>>
>> Older versions of IOS (12.2 and again some switches) take the path that
>> they
>> hear about first. On the other hand, more recent versions of IOS choose
>> the
>> path with the lowest AS number.* Just a sort of tie breaker*.
>>
>> But what if your boss the guy with that expensive tie and belt keeps
>> saying
>> "load balancing"?! I always believe when something obvious (even in IOS
>> 15)
>> is not there probably it should not be! but how would you save your team?
>>
>>
>>
>> Kambiz Agahian
>> CCIE Instructor/Consultant
>> M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA
>>
>>
>> On Fri, Aug 27, 2010 at 10:42 AM, Kambiz Agahian<aussiecert_at_gmail.com
>> >wrote:
>>
>> Yeah as the otehr user posted the link and I asked before, you will see
>>> either the route picked based on timestamp OR based on AS numbers. With
>>> the
>>> IOS version you're using (12.4T) the one with the lower AS number takes
>>> precedence. But again, this is still the case with old versions of IOS
>>> and I
>>> believe still some switches.
>>>
>>>
>>> HTH
>>>
>>>
>>> Kambiz Agahian
>>> CCIE Instructor/Consultant
>>> M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA
>>>
>>>
>>> On Fri, Aug 27, 2010 at 9:49 AM, HEMANTH RAJ<hemanthrj_at_gmail.com>
>>> wrote:
>>>
>>> No wat i have done first with AS 100 and then AS 200. It goes thorugh AS
>>>> 100
>>>> And then created another interface with another in AS 50 ,then
>>>> afterwards
>>>> it is goin via AS 50
>>>> tats the confusing point!!!
>>>>
>>>>
>>>> On Fri, Aug 27, 2010 at 10:17 PM, Kambiz Agahian<aussiecert_at_gmail.com
>>>> >wrote:
>>>>
>>>> The one with a lower number or the one to be seen first?
>>>>>
>>>>> Kambiz Agahian
>>>>> CCIE Instructor/Consultant
>>>>> M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA
>>>>>
>>>>> On Fri, Aug 27, 2010 at 9:43 AM, HEMANTH RAJ<hemanthrj_at_gmail.com
>>>>> >wrote:
>>>>>
>>>>> yes Vince u r right it chooses the one with a lower Autonomous system
>>>>>> .Experts pls guide me for this question.
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Fri, Aug 27, 2010 at 11:35 AM, Vince Librandi<
>>>>>> vlibrandi_at_internode.on.net
>>>>>>
>>>>>>> wrote:
>>>>>>> Woops forgot to add the answer to your question.
>>>>>>>
>>>>>>> The router will only choose use the routes for a prefix from one
>>>>>>>
>>>>>> routing
>>>>>>
>>>>>>> protocol because that way it can guarantee at least for that AS it
>>>>>>> has
>>>>>>>
>>>>>> a
>>>>>>
>>>>>>> loop free path for the prefix (of course redistribution can negate
>>>>>>>
>>>>>> that).
>>>>>>
>>>>>>> But if the router where to install one route from one AS and another
>>>>>>>
>>>>>> from a
>>>>>>
>>>>>>> second AS it wouldn't be able to be sure that the path doesn't loop
>>>>>>> somewhere as the two AS's don't share routing information.
>>>>>>>
>>>>>>> So it looks like the router chooses the lowest AS number when the
>>>>>>>
>>>>>> prefix
>>>>>>
>>>>>>> length and AD are the same for a prefix.
>>>>>>>
>>>>>>>
>>>>>>> On 27/08/2010 3:05 PM, Vince Librandi wrote:
>>>>>>>
>>>>>>> Hi Hemanth,
>>>>>>>>
>>>>>>>> I just lab'ed up your set up and got the same affect. Looks like
>>>>>>>> when
>>>>>>>>
>>>>>>> you
>>>>>>
>>>>>>> have two EIGRP process and the metric is the same and the AD on the
>>>>>>>>
>>>>>>> route is
>>>>>>
>>>>>>> the same the router chooses the process with the lowest AS number.
>>>>>>>>
>>>>>>> Just to
>>>>>>
>>>>>>> prove it I configured another EIGRP process (AS 50) on the R5-R4 link
>>>>>>>>
>>>>>>> and
>>>>>>
>>>>>>> the router choose that path instead.
>>>>>>>>
>>>>>>>> R5(config-router)#do sh ip ei top
>>>>>>>> IP-EIGRP Topology Table for AS(100)/ID(10.1.45.5)
>>>>>>>>
>>>>>>>> Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
>>>>>>>> r - reply Status, s - sia Status
>>>>>>>>
>>>>>>>> P 1.1.1.1/32, 0 successors, FD is Inaccessible
>>>>>>>> via 10.1.35.3 (3097600/2585600), Serial0/1
>>>>>>>>
>>>>>>>> IP-EIGRP Topology Table for AS(200)/ID(1.1.1.2)
>>>>>>>>
>>>>>>>> Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
>>>>>>>> r - reply Status, s - sia Status
>>>>>>>>
>>>>>>>> P 1.1.1.1/32, 0 successors, FD is Inaccessible
>>>>>>>> via 10.1.45.4 (3097600/2585600), Serial0/0
>>>>>>>>
>>>>>>>> IP-EIGRP Topology Table for AS(50)/ID(10.1.45.5)
>>>>>>>>
>>>>>>>> Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
>>>>>>>> r - reply Status, s - sia Status
>>>>>>>>
>>>>>>>> P 1.1.1.1/32, 1 successors, FD is 3097600
>>>>>>>> via 10.1.45.4 (3097600/2585600), Serial0/0
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> but if both links are in the same AS then I get the load balancing
>>>>>>>>
>>>>>>>> R5(config-router)#do sh ip ei top
>>>>>>>> IP-EIGRP Topology Table for AS(100)/ID(10.1.45.5)
>>>>>>>>
>>>>>>>> Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
>>>>>>>> r - reply Status, s - sia Status
>>>>>>>>
>>>>>>>> P 1.1.1.1/32, 2 successors, FD is 3097600
>>>>>>>> via 10.1.35.3 (3097600/2585600), Serial0/1
>>>>>>>> via 10.1.45.4 (3097600/2585600), Serial0/0
>>>>>>>>
>>>>>>>> Looks like this is the way the routing table chooses between routes
>>>>>>>>
>>>>>>> handed
>>>>>>
>>>>>>> to it from different processes.
>>>>>>>>
>>>>>>>> Must see if OSPF does the same thing.
>>>>>>>>
>>>>>>>> Regards
>>>>>>>>
>>>>>>>> Vince
>>>>>>>>
>>>>>>>>
>>>>>>>> On 27/08/2010 1:21 PM, HEMANTH RAJ wrote:
>>>>>>>>
>>>>>>>> s0/1 s0/0
>>>>>>>>> R2-------------------R3\s 0/2
>>>>>>>>> | | \
>>>>>>>>> |s0/0 s0/3 | \
>>>>>>>>> | | \ R1-loo 0
>>>>>>>>> 1.1.1.1/24
>>>>>>>>> | | \ s 0/0 R1-loo 1
>>>>>>>>> 11.11.11.11/24
>>>>>>>>> | | \
>>>>>>>>> | | / R5 R2-loo o
>>>>>>>>>
>>>>>>>> 2.2.2.2
>>>>>>
>>>>>>> /24
>>>>>>>>> | | / R2-loo 1
>>>>>>>>> 22.22.22.22/24
>>>>>>>>> | | / s 0/1
>>>>>>>>> | | /
>>>>>>>>> | s0/0 | /
>>>>>>>>> | s0/3 | /s0/2
>>>>>>>>> R1-------------------R4
>>>>>>>>> s0/1 s0/0
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I'm running ospf area 0 on R1,R2,R3 s 0/0,R4 s0/0
>>>>>>>>>
>>>>>>>>> R3 s0/3 ospf area 20
>>>>>>>>> R4 s0/3 ospf area 20
>>>>>>>>>
>>>>>>>>> R3 s0/2 eigrp AS 100
>>>>>>>>> R5 s0/0 eigrp AS 100
>>>>>>>>>
>>>>>>>>> R4 s0/2 eigrp AS 200
>>>>>>>>> R5 s0/1 eigrp AS 200
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> I have done mutual redistribution on R3 between OSPF and EIGRP 100
>>>>>>>>>
>>>>>>>>> I have done mutual redistribution on R4 between OSPF and EIGRP 200
>>>>>>>>>
>>>>>>>>> Every route can ping every other route
>>>>>>>>>
>>>>>>>>> But when i check on R5 routing table I'm learning R1's loopback0
>>>>>>>>> via
>>>>>>>>>
>>>>>>>> R3
>>>>>>
>>>>>>> But as per the logic it should load balance between R3 and R4 but it
>>>>>>>>>
>>>>>>>> is
>>>>>>
>>>>>>> choosing only R3
>>>>>>>>> and when i check on R5 topology table it shows the route via R4 is
>>>>>>>>> inaccessible
>>>>>>>>>
>>>>>>>>> I have reidstributed from opsf to eigrp with same metric on both R3
>>>>>>>>>
>>>>>>>> and
>>>>>>
>>>>>>> R4
>>>>>>>>>
>>>>>>>>> R3
>>>>>>>>> router eigrp 100
>>>>>>>>> redis ospf 1 met 1 1 1 1 1
>>>>>>>>>
>>>>>>>>> R4
>>>>>>>>> router eigrp 200
>>>>>>>>> redis ospf 1 met 1 1 1 1 1
>>>>>>>>>
>>>>>>>>> But still R5 is choosing path via R3 and not loadbalancing between
>>>>>>>>>
>>>>>>>> R3 and
>>>>>>
>>>>>>> R4
>>>>>>>>>
>>>>>>>>> Can anyone help me out of this issue???
>>>>>>>>>
>>>>>>>>>
>>>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>>>
>>>>>>>>
>>>>>>>> _______________________________________________________________________
>>>>>>
>>>>>>> Subscription information may be found at:
>>>>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>> --
>>>>>> Problems arise Bcoz we talk,prblms r not solve bcoz we dont talk So
>>>>>> gud
>>>>>> r
>>>>>> bad talk to ur affectionate one's freely
>>>>>>
>>>>>> Urs Friendly,
>>>>>> HP HEMANTH RAJ
>>>>>>
>>>>>>
>>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>>
>>>>>>
>>>>>> _______________________________________________________________________
>>>>>> Subscription information may be found at:
>>>>>> http://www.groupstudy.com/list/CCIELab.html
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>> --
>>>> Problems arise Bcoz we talk,prblms r not solve bcoz we dont talk So gud
>>>> r
>>>> bad talk to ur affectionate one's freely
>>>>
>>>> Urs Friendly,
>>>> HP HEMANTH RAJ
>>>>
>>>
>> Blogs and organic groups at http://www.ccie.net
>>
>> _______________________________________________________________________
>> Subscription information may be found at:
>> http://www.groupstudy.com/list/CCIELab.html

Blogs and organic groups at http://www.ccie.net
Received on Sat Aug 28 2010 - 08:24:42 ART