From: Private Ryan (pv.ryan@gmail.com)
Date: Wed Sep 21 2005 - 09:21:05 GMT-3
it is a funny result that cisco always makes its stuff the best
=)
2005/9/21, Carlos G Mendioroz <tron@huapi.ba.ar>:
> Sorry,
> was just browsing and could not resist to chime in (without reviewing
> all the thread).
>
> I remember a similar topic, and the answer was... that the router does
> not compare different protocol routes even if AD is the same.
> There is like a default hierarchy where EIGRP is better than OSPF is
> better than RIP... and even if you place the same AD for all, EIGRP will
> win (given routes to same CIDR) no matter what its costs are.
>
>
>
> sundar.palaniappan@verizon.com @ 20/09/2005 21:39 dixit:
> > The question here is not what's the GENERIC process for route selection.
> > Thing that was brought up is when TWO protocols have the same distance, how
> > does a router decide which one to use or does it load balance. Your
> > response doesn't address the subject.
> >
> > See the results for yourself below.
> >
> >
> > R2#show run
> > Building configuration...
> >
> > (output edited to retain context)
> > !
> > interface Loopback0
> > ip address 2.2.2.2 255.255.255.255
> > !
> > interface Loopback1
> > ip address 11.11.11.11 255.255.255.255
> > !
> > interface Ethernet0
> > ip address 10.110.110.2 255.255.255.0
> > !
> > router eigrp 100
> > network 2.0.0.0
> > network 10.0.0.0
> > no auto-summary
> > !
> > router ospf 1
> > log-adjacency-changes
> > network 2.2.2.2 0.0.0.0 area 1
> > network 10.0.0.0 0.255.255.255 area 0
> > network 11.0.0.0 0.255.255.255 area 1
> >
> >
> >
> > R3#show run
> > Building configuration...
> > !
> > interface Ethernet0
> > ip address 10.110.110.3 255.255.255.0
> > !
> > router eigrp 100
> > network 10.0.0.0
> > no auto-summary
> > !
> > router ospf 1
> > log-adjacency-changes
> > network 10.0.0.0 0.255.255.255 area 0
> > distance 90 11.11.11.11 0.0.0.0 1
> > !
> > access-list 1 permit any
> >
> >
> >
> > R3#show ip eigrp nei
> > IP-EIGRP neighbors for process 100
> > H Address Interface Hold Uptime SRTT RTO Q Seq
> > Type
> > (sec) (ms) Cnt Num
> > 0 10.110.110.2 Et0 10 01:34:39 959 5000 0 9
> > R3#show ip ospf nei
> >
> > Neighbor ID Pri State Dead Time Address Interface
> > 11.11.11.11 1 FULL/DR 00:00:37 10.110.110.2 Ethernet0
> > R3#show ip route
> > Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP
> > i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS
> > level-2
> > ia - IS-IS inter area, * - candidate default, U - per-user static
> > route
> > o - ODR, P - periodic downloaded static route
> >
> > Gateway of last resort is not set
> >
> > 2.0.0.0/32 is subnetted, 1 subnets
> > D 2.2.2.2 [90/409600] via 10.110.110.2, 00:00:01, Ethernet0
> > 10.0.0.0/24 is subnetted, 1 subnets
> > C 10.110.110.0 is directly connected, Ethernet0
> > 11.0.0.0/32 is subnetted, 1 subnets
> > O IA 11.11.11.11 [90/11] via 10.110.110.2, 00:00:01, Ethernet0
> >
> > HTH,
> > Sundar Palaniappan
> > CCIE #14532
> >
> >
> >
> >
> >
> > "mani poopal"
> > <mani_ccie@yahoo. To: Sundar X. Palaniappan/EMPL/PA/Verizon@VZNotes,
> > com> "Dan Espino" <drespino@gmail.com>
> > Sent by: cc: ccielab@groupstudy.com, nobody@groupstudy.com,
> > nobody@groupstudy rosybird@gmail.com
> > .com Subject: Re: Administrative distance tie
> >
> >
> > 09/20/2005 07:10
> > PM
> > Please respond to
> > "mani poopal"
> >
> >
> >
> >
> >
> >
> > Guys,
> >
> > Simple rule in Cisco, if a route is learned by more than one routing
> > protocols or same routing protocols, selection in the routing table is
> > based on:
> > 1. Longest prefix
> > 2. Lowest AD(administrative distance)
> > 3. If same AD(same routing protocols), Lowest Metric(for rip hop count,
> > ospf cost etc)
> > 4. If Metric also same, then all routing protocols support equal cost path
> > load balancing
> > 5. When metrics are different and if you want to do load balancing, it is
> > called unequal cost path load balancing, only cisco's protocol(igrp and
> > eigrp) support this feature by variance command.
> >
> > hope this helps for beginers
> >
> >
> > Mani
> >
> > sundar.palaniappan@verizon.com wrote:
> > Comparing metric of two different protocols would be like comparing apples
> > and oranges.
> >
> > I believe, the protocol that owns the native administrative distance wins.
> > Let's say, a router learns NET X via RIP & OSPF and you lower the distance
> > to 110 for the RIP route, router will install the OSPF route in the routing
> > table and not the RIP route.
> >
> > I don't have any documented explanation for the behavior. But, it makes
> > sense the IOS prefers the native admin distance over the modified one when
> > both are same.
> >
> > HTH,
> > Sundar Palaniappan
> > CCIE #14532
> >
> >
> >
> > "Dan Espino"
> > om> cc:
> > Sent by: Subject: Re: Administrative distance tie
> > nobody@groupstudy
> > .com
> >
> >
> > 09/20/2005 05:10
> > PM
> > Please respond to
> > "Dan Espino"
> >
> >
> >
> >
> >
> >
> > OK, rip had a hop count to 3 and ospf has a cost of 10.
> > Now who wins
> >
> >
> > On 9/20/05, rosy bird wrote:
> >
> >>i guess...here is where metric comes into picture...
> >>
> >>On 9/21/05, Dan Espino wrote:
> >>
> >>>If 2 protocols have the same AD (because one was adjusted), and the
> >
> > same
> >
> >>>prefix length, how does the router determine which to choose?
> >>>
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>
> --
> Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
>
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