Hi, I am not to sure myself here. I will ask one of my colleagues here as well to see if he has any light that he can shed here.
Regards Andrew -----Original Message----- From: Diffy De Villiers [mailto:[EMAIL PROTECTED]] Sent: 14 January 2002 13:01 PM To: [EMAIL PROTECTED] Subject: URGENT - PLEASE HELP - OSPF summary route cost. [7:31832] Hi Everybody This is the third time that I am posting this message to this studygroup, I had no reply to the previous two postings. Hopefully someone will be able to assist me this time. I have a problem understanding how costs are calculated for OSPF summary routes. To understand my problem refer to the following example: This is the internetwork diagram (with 4 routers A,B,C & D): netw 1 netw 2 netw 3 netw 4 [ A ]--------[ B ]--------[ C ]---------[ D ]---------| cost 1 cost 4 cost 64 cost 16 ---------------------------------- Here are my router configurations: ---------------------------------- hostname RouterA ! interface Serial0 description connected to RouterB via network 1 ip address 192.168.1.2 255.255.255.0 ip ospf cost 1 no fair-queue ! router ospf 10 network 192.168.1.0 0.0.0.255 area 1 -------------------------------------- hostname RouterB ! interface Ethernet0 description connected to RouterC via network 2 ip address 192.168.2.1 255.255.255.0 ip ospf cost 4 ! interface Serial0 description connected to RouterA via network 1 ip address 192.168.1.1 255.255.255.0 ip ospf cost 1 ! router ospf 10 network 192.168.1.0 0.0.0.255 area 1 network 192.168.2.0 0.0.0.255 area 0 -------------------------------------- hostname RouterC ! interface Ethernet0 description connected to RouterB via network 2 ip address 192.168.2.2 255.255.255.0 ip ospf cost 4 ! interface Serial0 description connected to RouterD via network 3 ip address 192.168.3.1 255.255.255.0 ip ospf cost 64 ! router ospf 10 network 192.168.2.0 0.0.0.255 area 0 network 192.168.3.0 0.0.0.255 area 2 -------------------------------------- hostname RouterD ! interface Ethernet0 description network 4 ip address 192.168.4.1 255.255.255.0 ip ospf cost 16 ! interface Serial0 description connected to RouterC via network 3 ip address 192.168.3.2 255.255.255.0 ip ospf cost 64 no fair-queue ! router ospf 10 network 192.168.3.0 0.0.0.255 area 2 network 192.168.4.0 0.0.0.255 area 2 -------------------------------------- If we do a "show ip route" at routerA we get the following output: RouterA>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, * - candidate default U - per-user static route, o - ODR Gateway of last resort is not set C 192.168.1.0/24 is directly connected, Serial0 O IA 192.168.2.0/24 [110/5] via 192.168.1.1, 00:23:26, Serial0 O IA 192.168.3.0/24 [110/133] via 192.168.1.1, 00:18:51, Serial0 O IA 192.168.4.0/24 [110/85] via 192.168.1.1, 00:18:56, Serial0 Now for my problem: Looking at the diagram above, the metric from Router A to network 4 is 85. This is perfectly understandable (sumtotal of all the costs: 85 = 1+4+64+16). BUT NOW: The metric from RouterA to network 3 is 133!!! This is higher than the metric to network 4 even though we access network 4 via network 3. Logically I would have thought the cost to network 3 has to be 69 (64+4+1), not 133. Where does the cost-difference of 64 come from? The only rational explanation I have for this is that the ABR for area 2 added it, but why??? And why only add this cost factor for network 3 (and not for network 4)??? Please assist me if you know the answers since I cannot figure out a reasonable explanation. Thank you for your support. Abraham de Villiers Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=31834&t=31832 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
