From: Adam Quiggle (aquiggle@xxxxxxxxx)
Date: Sun Feb 10 2002 - 03:37:03 GMT-3
Hi Gang,
Running through Lab 9 and think I am finally coming to the realization
about VLSM->FLSM on different classfull networks. Previously I had
thought that any route that is injected into a FLSM that the VLSM route
had to be summarized to the classfull network boundary before it would
get advertised into the FLSM. For example:
Simple Scenario:
R1(s1)---IGRP----(S0.2)R2(S0.1)----OSPF DOMAIN
Objective: Redistribute OSPF into IGRP.
OSPF Routes on R2:
R2#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
137.20.0.0/24 is subnetted, 1 subnets
C 137.20.20.0 is directly connected, Ethernet0
172.168.0.0/16 is variably subnetted, 2 subnets, 2 masks
O IA 172.168.10.0/24 [110/65] via 150.100.32.10, 00:11:27, Serial0.1
O IA 172.168.64.0/18 [110/138] via 150.100.32.10, 00:11:27, Serial0.1
150.100.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 150.100.32.0/19 is directly connected, Serial0.1
O 150.100.32.4/32 [110/128] via 150.100.32.10, 00:11:27, Serial0.1
O 150.100.32.10/32 [110/64] via 150.100.32.10, 00:11:28, Serial0.1
150.200.0.0/20 is subnetted, 1 subnets
C 150.200.16.0 is directly connected, Serial0.2
I 150.150.0.0/16 [100/8976] via 150.200.16.1, 00:00:40, Serial0.2
NOTICE: 172.168.0.0/16 is variably subnetted with no summarization
being performed anywhere.
R2 Config:
router ospf 10
router-id 2.2.2.2
log-adjacency-changes
redistribute igrp 10 metric 100 metric-type 1 subnets tag 1
network 137.20.20.0 0.0.0.255 area 2
network 150.100.32.0 0.0.31.255 area 0
!
router igrp 10
redistribute ospf 10
passive-interface Ethernet0
passive-interface Serial0.1
network 150.200.0.0
default-metric 1500 100 255 1 1500
On R1 I see the networks on a classfull boundary without any
summarization at all.
R1#show ip route igrp
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
I 137.20.0.0/16 [100/8576] via 150.200.16.2, 00:01:11, Serial1
I 172.168.0.0/16 [100/8766] via 150.200.16.2, 00:01:11, Serial1
I 150.100.0.0/16 [100/10476] via 150.200.16.2, 00:01:11, Serial1
It never dawned on me that when dealing with different classfull
networks you don't have to worry about getting the subnet mask correct
to get your route injected into a FLSM network.
My question: Is this the correct behavior?
Thanks in advance,
AQ
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