Re: Redistribution Problem

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
>>>> >>
>>>> >>
>>>> _______________________________________________________________________
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>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >>
>>>> >
>>>>
>>>>
>>>> --
>>>> 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:
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>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>>
>> --
>> 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

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Received on Fri Aug 27 2010 - 15:58:52 ART