From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Fri Dec 23 2005 - 21:55:01 GMT-3
Remember that all inter-area traffic must transit area 0 (an ABR). It doesn't matter what the cost is to reach R3's loopback which is in area 2 across the Ethernet segment that is area 3.
To reach a route in area 2 the traffic must use the area 0 path over the path across area 3. If you want to "transit" area 3 to reach area 2 look into using a virtual-link across the Ethernet or a tunnel.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
________________________________________
From: Zukque [mailto:zukque@gmail.com]
Sent: Friday, December 23, 2005 3:06 PM
To: Brian Dennis
Cc: Cisco certification
Subject: Re: IP OSPF COST for IA's
Thanks for your help, this is a very simple topology..sorry not good drawing also :)
R2 is the Hub
R3 and R4 are the spokes
R4 is also conected to R2 via Ethernet
Lo0 3.3.3.3/32
!
R3 -S0-------------------------------
---------------------------------------S0-R2 -Lo0 2.2.2.2/32
R4-S0--------------------------------- |
Eth-----------------------------------Eth
R3 Lo0 belongs to area 2
R2, R3, R4 S0s are in area 0
R4 Eth to R2 Ethe si in area 3
R2 is redistributing this Lo0 in OSPF using the default type
------------------------------------------------
R2
interface Ethernet0
ip address 183.1.42.2 255.255.255.0
!
interface Serial0
ip address 183.1.0.2 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
no frame-relay inverse-arp
frame-relay map ip 183.1.0.3 203 broadcast
frame-relay map ip 183.1.0.4 204 broadcast
!
router ospf 1
log-adjacency-changes
redistribute connected subnets route-map Lo0
network 183.1.0.0 0.0.0.255 area 0
network 183.1.42.2 0.0.0.0 area 3
!
-----------------------------------------------
R3:
!
interface Loopback0
ip address 3.3.3.3 255.255.255.255
interface Serial0
ip address 183.1.0.3 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
frame-relay map ip 183.1.0.2 302 broadcast
frame-relay map ip 183.1.0.4 302
no frame-relay inverse-arp
router ospf 1
log-adjacency-changes
network 3.3.3.3 0.0.0.0 area 23
network 183.1.0.0 0.0.0.255 area 0
------------------------------------------
R4:
interface Loopback0
ip address 4.4.4.4 255.255.255.255
ip ospf network point-to-point
!
interface Ethernet0
ip address 183.1.42.4 255.255.255.0
ip ospf priority 0
interface Serial0
ip address 183.1.0.4 255.255.255.0
encapsulation frame-relay
ip ospf network point-to-multipoint
ip ospf cost 1000
ip ospf priority 0
frame-relay map ip 183.1.0.2 402 broadcast
frame-relay map ip 183.1.0.3 402
no frame-relay inverse-arp
On 12/23/05, Brian Dennis <bdennis@internetworkexpert.com> wrote:
Can you post your configurations and a little information about the topology?
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
________________________________________
From: Zukque [mailto: zukque@gmail.com]
Sent: Friday, December 23, 2005 1:37 PM
To: Brian Dennis
Cc: Cisco certification
Subject: Re: IP OSPF COST for IA's
Brain, but why to get to route 3.3.3.3 the router is choosing S0, E0 has a better cost
On 12/23/05, Brian Dennis < bdennis@internetworkexpert.com> wrote:
You have four OSPF routes in your routing table:
2.0.0.0/24 is subnetted, 1 subnets
O E2 2.2.2.0 [110/20] via 183.1.0.2, 00:24:45, Serial0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/129] via 183.1.0.2, 00:24:45, Serial0
O 183.1.0.2/32 [110/64] via 183.1.0.2, 00:31:22, Serial0
O 183.1.0.3/32 [110/128] via 183.1.0.2, 00:31:24, Serial0
You adjusted the OSPF cost on the interface to 1000:
2.0.0.0/24 is subnetted, 1 subnets
O E2 2.2.2.0 [110/20] via 183.1.42.2, 00:01:24, Ethernet0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/1065] via 183.1.0.2, 00:01:24, Serial0
4.0.0.0/32 is subnetted, 1 subnets
O 183.1.0.2/32 [110/1000] via 183.1.0.2, 00:01:24, Serial0
O 183.1.0.3/32 [110/1064] via 183.1.0.2, 00:01:25, Serial0
All of the intra and inter area routes cost have changed. The only
route that did not change is the E2 route which as you know should not
change.
As per RFC 2328:
Cost
The link state cost of the path to the destination. For all
paths except type 2 external paths this describes the entire
path's cost. For Type 2 external paths, this field describes
the cost of the portion of the path internal to the AS. This
cost is calculated as the sum of the costs of the path's
constituent links.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Zukque
Sent: Friday, December 23, 2005 11:50 AM
To: Cisco certification
Subject: IP OSPF COST for IA's
Dears
Why IA OSPF route's are not affected with the ip ospf cost command?
Is there a preference for Intra / Inter / External Route? Please can you
show me where I can find this in 2328
Thanks!
That is: (take a look at 3.3.3.3)
R#show ip ospf neighbor
Neighbor ID Pri State Dead Time Address
Interface
183.1.0.2 1 FULL/ - 00:01:51 183.1.0.2
Serial0
183.1.0.2 1 FULL/BDR 00:00:33 183.1.42.2
Ethernet0
R#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, 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
2.0.0.0/24 is subnetted, 1 subnets
O E2 2.2.2.0 [110/20] via 183.1.0.2, 00:24:45, Serial0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/129] via 183.1.0.2, 00:24:45, Serial0
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
183.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
C 183.1.42.0/24 is directly connected, Ethernet0
O 183.1.0.2/32 [110/64] via 183.1.0.2, 00:31:22, Serial0
O 183.1.0.3/32 [110/128] via 183.1.0.2, 00:31:24, Serial0
C 183.1.0.0/24 is directly connected, Serial0
R#
R(config)#interface s0
R(config-if)#ip ospf cost 1000
R(config-if)#^Z
R#clear ip route *
3d16h: RT: add 183.1.42.0/24 via 0.0.0.0, connected metric [0/0]
3d16h: RT: add 4.4.4.4/32 via 0.0.0.0, connected metric [0/0]
3d16h: RT: add 183.1.0.0/24 via 0.0.0.0, connected metric [0/0]
3d16h: RT: network 183.1.0.0 is now variably masked
3d16h: RT: add 183.1.0.2/32 via 183.1.0.2, ospf metric [110/1000]
3d16h: RT: add 183.1.0.3/32 via 183.1.0.2, ospf metric [110/1064]
3d16h: RT: add 3.3.3.3/32 via 183.1.0.2, ospf metric [110/1065]
3d16h: RT: add 2.2.2.0/24 via 183.1.42.2, ospf metric [110/20]
R#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, 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
2.0.0.0/24 is subnetted, 1 subnets
O E2 2.2.2.0 [110/20] via 183.1.42.2, 00:01:24, Ethernet0
3.0.0.0/32 is subnetted, 1 subnets
O IA 3.3.3.3 [110/1065] via 183.1.0.2, 00:01:24, Serial0
4.0.0.0/32 is subnetted, 1 subnets
C 4.4.4.4 is directly connected, Loopback0
183.1.0.0/16 is variably subnetted, 4 subnets, 2 masks
C 183.1.42.0/24 is directly connected, Ethernet0
O 183.1.0.2/32 [110/1000] via 183.1.0.2, 00:01:24, Serial0
O 183.1.0.3/32 [110/1064] via 183.1.0.2, 00:01:25, Serial0
C 183.1.0.0/24 is directly connected, Serial0
R#show ip ospf database
OSPF Router with ID (183.1.0.4) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link
count
183.1.0.2 183.1.0.2 427 0x80000010 0x4A1C 3
183.1.0.3 183.1.0.3 1444 0x80000007 0xDD56 2
183.1.0.4 183.1.0.4 232 0x80000013 0xEE87 2
Summary Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
3.3.3.3 183.1.0.3 1701 0x80000002 0x77FB
183.1.42.0 183.1.0.2 427 0x8000000B 0xBD69
183.1.42.0 183.1.0.4 1480 0x80000009 0x4014
Summary ASB Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
183.1.0.2 183.1.0.4 1944 0x80000004 0xF788
183.1.0.4 183.1.0.2 179 0x80000004 0x65ED
Router Link States (Area 3)
Link ID ADV Router Age Seq# Checksum Link
count
183.1.0.2 183.1.0.2 51 0x8000000A 0x66CA 2
183.1.0.4 183.1.0.4 53 0x8000000B 0xB8C9 2
Net Link States (Area 3)
Link ID ADV Router Age Seq# Checksum
183.1.42.2 183.1.0.2 51 0x80000001 0x1D06
183.1.42.4 183.1.0.4 959 0x80000005 0xEC2E
Summary Net Link States (Area 3)
Link ID ADV Router Age Seq# Checksum
3.3.3.3 183.1.0.2 1691 0x80000002 0xFF34
3.3.3.3 183.1.0.4 228 0x80000004 0x2321
183.1.0.2 183.1.0.2 1194 0x80000004 0x853F
183.1.0.2 183.1.0.4 228 0x80000004 0xAD29
183.1.0.3 183.1.0.2 1194 0x80000004 0xFD85
183.1.0.3 183.1.0.4 228 0x80000004 0x2570
183.1.0.4 183.1.0.2 429 0x80000002 0xF78C
183.1.0.4 183.1.0.4 1482 0x80000002 0x6959
Summary ASB Link States (Area 3)
Link ID ADV Router Age Seq# Checksum
183.1.0.2 183.1.0.4 228 0x80000004 0x9F36
183.1.0.4 183.1.0.2 429 0x80000002 0xE999
Type-5 AS External Link States
Link ID ADV Router Age Seq# Checksum Tag
2.2.2.0 183.1.0.2 429 0x80000004 0x10CC 0
4.4.4.4 183.1.0.4 214 0x80000004 0x933D 0
Thanks !!!!
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