From: Baety Wayne A1C 18 CS/SCBX (Wayne.Baety@xxxxxxxxxxxxx)
Date: Sun Feb 10 2002 - 21:16:31 GMT-3
Not necessarily always a classful networking boundary, but to the prefix
size that a FLSM routing domain uses.
[OSPF] Summarization point to /27's [IGRP]
/
(VLSM nets,/25's,/28's etc...) A---B---C (FLSM /27 prefixes)
WAYNE BAETY, MCSE, A1C, USAF
Network Systems Trainer
> -----Original Message-----
> From: Adam Quiggle [mailto:aquiggle@nc.rr.com]
> Sent: Sunday, February 10, 2002 3:37 PM
> To: ccielab@groupstudy.com
> Subject: Bootcamp Lab 9, VLSM->FLSM
>
> 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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