Re: Redistribution Problem

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???
> >>>
> >>
> >>
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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 - 09:47:20 ART