From: sundar.palaniappan@verizon.com
Date: Tue Sep 20 2005 - 21:39:01 GMT-3
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?
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
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