From: Lassak, Mike (mikel@xxxxxxxxxx)
Date: Tue Jun 04 2002 - 14:55:30 GMT-3
I believe it has to do with the longest match rule. EIGRP is summarizing
the routes with /24 but OSPF is seeing the loopback on R6 as a host address
therefore using the longest match /32.
-----Original Message-----
From: Nick Lesewski [mailto:nickless9@hotmail.com]
Sent: Tuesday, June 04, 2002 1:09 PM
To: ccielab@groupstudy.com
Subject: routing protocol puzzle
I've been playing with AD and I've got something confusing. I've got six
routers layed out like this:
R2---R3
/ \
R1 R6
\ /
R4---R4
Routers R2 and R3 are only running EIGRP.
Routers R4 and R5 are only running OSPF.
Routers R1 and R6 are running both.
There is no redistribution between the two protocols.
R6 has a loopback interface that is being advertised through a network
statement in each of the two protocols.
I would expect R1 to see the loopback on R6 through both protocols, but then
selected EIGRP, since it has a lower AD. What happens is that OSPF provides
a /32 route that takes precidence over the /24 route provided by EIGRP. It
seems like OSPF is finding the specific address of the loopback interface,
while EIGRP is finding the whole class-C network, so OSPF is taking control.
My question is... why?
Here are my configs...
R1#show run
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname R1
!
no logging console
enable password cisco
!
ip subnet-zero
no ip domain-lookup
!
interface Loopback0
ip address 192.168.1.1 255.255.255.0
no ip directed-broadcast
!
interface Serial1/0
ip address 192.168.14.1 255.255.255.0
no ip directed-broadcast
encapsulation ppp
no ip mroute-cache
no fair-queue
!
interface Serial1/1
ip address 192.168.12.1 255.255.255.0
no ip directed-broadcast
encapsulation ppp
!
router eigrp 21
network 192.168.1.0
network 192.168.12.0
!
router ospf 12
network 192.168.1.0 0.0.0.255 area 0
network 192.168.14.0 0.0.0.255 area 0
!
ip classless
no ip http server
!
alias exec i show ip route
alias exec co config t
!
line con 0
exec-timeout 0 0
password cisco
login
transport input none
line aux 0
exec-timeout 0 0
password cisco
login
line vty 0 4
exec-timeout 0 0
password cisco
login
!
end
R2#show run
!
interface Loopback0
ip address 192.168.2.2 255.255.255.0
!
interface Serial0
ip address 192.168.23.2 255.255.255.0
encapsulation ppp
no ip route-cache
no ip mroute-cache
clockrate 125000
!
interface Serial1
ip address 192.168.12.2 255.255.255.0
encapsulation ppp
no ip route-cache
no ip mroute-cache
clockrate 125000
!
router eigrp 21
network 192.168.2.0
network 192.168.12.0
network 192.168.23.0
auto-summary
no eigrp log-neighbor-changes
R3#sh run
!
interface Loopback0
ip address 192.168.3.3 255.255.255.0
!
interface Serial0
ip address 192.168.23.3 255.255.255.0
encapsulation ppp
no ip route-cache
no ip mroute-cache
!
interface Serial1
ip address 192.168.36.3 255.255.255.0
encapsulation ppp
no ip route-cache
no ip mroute-cache
clockrate 125000
!
router eigrp 21
redistribute connected
network 192.168.23.0
network 192.168.36.0
default-metric 1000 10 1 255 1500
auto-summary
no eigrp log-neighbor-changes
R4#sh run
!
interface Loopback0
ip address 192.168.4.4 255.255.255.0
no ip directed-broadcast
!
interface Serial0
ip address 192.168.14.4 255.255.255.0
no ip directed-broadcast
encapsulation ppp
no ip mroute-cache
clockrate 125000
!
interface Serial1
ip address 192.168.45.4 255.255.255.0
no ip directed-broadcast
encapsulation ppp
!
router ospf 12
network 192.168.4.0 0.0.0.255 area 0
network 192.168.14.0 0.0.0.255 area 0
network 192.168.45.0 0.0.0.255 area 0
R5#sh run
!
interface Loopback0
ip address 192.168.5.5 255.255.255.0
!
interface Serial0
ip address 192.168.56.5 255.255.255.0
encapsulation ppp
clockrate 125000
!
interface Serial1
ip address 192.168.45.5 255.255.255.0
encapsulation ppp
clockrate 19200
!
interface BRI0
ip address 170.12.26.254 255.255.255.252
encapsulation ppp
!
router ospf 12
log-adjacency-changes
redistribute connected metric 100 subnets
network 192.168.45.0 0.0.0.255 area 0
network 192.168.56.0 0.0.0.255 area 0
R6#sh run
!
interface Loopback0
ip address 192.168.6.6 255.255.255.0
!
interface Serial0
ip address 192.168.56.6 255.255.255.0
encapsulation ppp
!
interface Serial1
ip address 192.168.36.6 255.255.255.0
encapsulation ppp
!
interface BRI0
ip address 170.12.26.253 255.255.255.252
encapsulation ppp
!
router eigrp 21
network 192.168.6.0
network 192.168.36.0
auto-summary
no eigrp log-neighbor-changes
!
router ospf 12
log-adjacency-changes
network 192.168.6.0 0.0.0.255 area 0
network 192.168.56.0 0.0.0.255 area 0
!
Any help in understanding what's going on is appreciated...
Thanks...
NIC
This archive was generated by hypermail 2.1.4 : Tue Jul 02 2002 - 08:12:23 GMT-3