From: ricky ong (longwaydown@live.com)
Date: Thu Sep 25 2008 - 06:47:46 ART
Hi all,
I am quite stuck at IWEB VOL2 4.1 LAB 13 Q3.7 when the question asked to prefer routes coming from R1 at R5's perspective. The question disallows ip ospf cost, bandwitch, virtual link, stub area.. then i tried to use distance command.. hoping to set the routes coming from R2 to a higher distance.. i used distance 111 150.1.2.2 0.0.0.0 Q3.7 to test.. but only to find that not only R2, but R1's distance are also set to 111.. see below config and output:
Rack1R5(config-router)#do sh run | s router os|route-|Q3.7router ospf 1 router-id 150.1.5.5 log-adjacency-changes network 139.1.15.5 0.0.0.0 area 1 network 139.1.25.5 0.0.0.0 area 1 network 150.1.5.5 0.0.0.0 area 1 distance 111 150.1.2.2 0.0.0.0 Q3.7ip prefix-list Q3.7 seq 5 permit 139.1.2.0/24ip access-list standard Q3.7 permit 139.1.0.0 0.0.0.255 permit 139.1.6.0 0.0.0.255Rack1R5(config-router)#do cle ip route *Rack1R5(config-router)#do sh ip route os 139.1.0.0/16 is variably subnetted, 14 subnets, 2 masksO IA 139.1.11.0/24 [110/65] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.13.0/24 [110/128] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.2.0/24 [110/65] via 139.1.25.2, 00:00:02, Serial1/0.2O IA 139.1.0.0/24 [111/138] via 139.1.25.2, 00:00:02, Serial1/0.2 <<<<changed [111/138] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<also changedO IA 139.1.6.0/24 [111/148] via 139.1.25.2, 00:00:02, Serial1/0!
.2 <<<<<changed [111/148] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<<also changedO IA 139.1.7.0/24 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.23.0/24 [110/128] via 139.1.25.2, 00:00:02, Serial1/0.2 150.1.0.0/16 is variably subnetted, 8 subnets, 2 masksO IA 150.1.7.7/32 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.6.6/32 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.3.3/32 [110/129] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/129] via 139.1.15.1, 00:00:02, Serial1/0.1O 150.1.2.2/32 [110/65] via 139.1.25.2, 00:00:02, Serial1/0.2O 150.1.1.1/32 [110/65] via 139.1.15.1, 00:00:02, Serial1/0.1
Then I took a look at the solution guide.. it says to use
distance 109 150.1.1.1 0.0.0.0 Q3.7
So i updated the config on R5 as followed:
Rack1R5(config-std-nacl)#do sh run | s router os|route-|Q3.7 router ospf 1 router-id 150.1.5.5 log-adjacency-changes network 139.1.15.5 0.0.0.0 area 1 network 139.1.25.5 0.0.0.0 area 1 network 150.1.5.5 0.0.0.0 area 1 distance 109 150.1.1.1 0.0.0.0 Q3.7ip prefix-list Q3.7 seq 5 permit 139.1.2.0/24ip access-list standard Q3.7 permit 139.1.0.0 0.0.0.255 permit 139.1.6.0 0.0.0.255
But i can't see the routing taking effect on the 2 prefixes match ACL Q3.7..
Rack1R5(config-std-nacl)#do sh ip route os 139.1.0.0/16 is variably subnetted, 14 subnets, 2 masksO IA 139.1.11.0/24 [110/65] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 139.1.13.0/24 [110/128] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 139.1.2.0/24 [110/65] via 139.1.25.2, 00:01:25, Serial1/0.2O IA 139.1.0.0/24 [110/138] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/138] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 139.1.6.0/24 [110/148] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/148] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 139.1.7.0/24 [110/139] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/139] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 139.1.23.0/24 [110/128] via 139.1.25.2, 00:01:25, Serial1/0.2 150.1.0.0/16 is variably subnetted, 8 subnets, 2 masksO IA 150.1.7.7/32 [110/139] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/139] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 150!
.1.6.6/32 [110/139] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/139] via 139.1.15.1, 00:01:25, Serial1/0.1O IA 150.1.3.3/32 [110/129] via 139.1.25.2, 00:01:25, Serial1/0.2 [110/129] via 139.1.15.1, 00:01:25, Serial1/0.1O 150.1.2.2/32 [110/65] via 139.1.25.2, 00:01:25, Serial1/0.2O 150.1.1.1/32 [110/65] via 139.1.15.1, 00:01:25, Serial1/0.1
Noticing that both 139.1.0.0 and 139.1.6.0 is having 2 equal cost path, and path to R1 happens to be listing behind the path towards R2.. I added in 139.1.11.0 in ACL Q3.7 test... then i found that 139.1.11.0's distance is being modified as expected:
Rack1R5(config-std-nacl)#do sh run | s router os|route-|Q3.7router ospf 1 router-id 150.1.5.5 log-adjacency-changes network 139.1.15.5 0.0.0.0 area 1 network 139.1.25.5 0.0.0.0 area 1 network 150.1.5.5 0.0.0.0 area 1 distance 109 150.1.1.1 0.0.0.0 Q3.7ip prefix-list Q3.7 seq 5 permit 139.1.2.0/24ip access-list standard Q3.7 permit 139.1.0.0 0.0.0.255 permit 139.1.6.0 0.0.0.255 permit 139.1.11.0 0.0.0.255Rack1R5(config-std-nacl)#do cle ip route *Rack1R5(config-std-nacl)#do sh ip route os 139.1.0.0/16 is variably subnetted, 14 subnets, 2 masksO IA 139.1.11.0/24 [109/65] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<<<<<<modifiedO IA 139.1.13.0/24 [110/128] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.2.0/24 [110/65] via 139.1.25.2, 00:00:02, Serial1/0.2O IA 139.1.0.0/24 [110/138] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/138] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<<<<<< not modiif!
iedO IA 139.1.6.0/24 [110/148] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/148] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.7.0/24 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.23.0/24 [110/128] via 139.1.25.2, 00:00:02, Serial1/0.2 150.1.0.0/16 is variably subnetted, 8 subnets, 2 masksO IA 150.1.7.7/32 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.6.6/32 [110/139] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.3.3/32 [110/129] via 139.1.25.2, 00:00:02, Serial1/0.2 [110/129] via 139.1.15.1, 00:00:02, Serial1/0.1O 150.1.2.2/32 [110/65] via 139.1.25.2, 00:00:02, Serial1/0.2O 150.1.1.1/32 [110/65] via 139.1.15.1, 00:00:02, Serial1/0.1
Then later i shut down the Serial1/0.2 link, i found all 3 networks (139.1.11.0, 139.1.0.0, 139.1.6.0) are being modified as expected..
Rack1R5(config-std-nacl)#int ser 1/0.2Rack1R5(config-subif)#shRack1R5(config-subif)#*Mar 1 07:55:53.278: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.2.2 on Serial1/0.2 from FULL to DOWN, Neighbor Down: Interface down or detached
Rack1R5(config-subif)#do cle ip route *Rack1R5(config-subif)#do sh ip route os 139.1.0.0/16 is variably subnetted, 14 subnets, 2 masksO IA 139.1.11.0/24 [109/65] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<modifiedO IA 139.1.13.0/24 [110/128] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.2.0/24 [110/193] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.0.0/24 [109/138] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<<modifiedO IA 139.1.6.0/24 [109/148] via 139.1.15.1, 00:00:02, Serial1/0.1 <<<<<modifiedO IA 139.1.7.0/24 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.25.0/24 [110/256] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 139.1.23.0/24 [110/192] via 139.1.15.1, 00:00:02, Serial1/0.1 150.1.0.0/16 is variably subnetted, 8 subnets, 2 masksO IA 150.1.7.7/32 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.6.6/32 [110/139] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.3.3/32!
[110/129] via 139.1.15.1, 00:00:02, Serial1/0.1O IA 150.1.2.2/32 [110/193] via 139.1.15.1, 00:00:02, Serial1/0.1O 150.1.1.1/32 [110/65] via 139.1.15.1, 00:00:02, Serial1/0.1
Sorry about the long winded illustration.. can anyone offer an explanation on this? Seems like there is a relationship between the order of the equal cost routes being listed in the routing table and the distance command?
(eventually i have to use area range on R2 to kill the specific routes so that R1 is preferred over R2.. that is the closest solution i can get given the question's requirement. The solution provided by the SG does not work in my case)
Cheers
Ricky
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