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Re: 問題ID:6025
ﾌｫｰﾗﾑ
最強WEB問題集CCNP ROUTE
投稿ﾕｰｻﾞ(投稿日)
(2013/5/27)
本文
【上位:RB-RC(〜RF)-RA:下位】とならないように構成を作ろうというのがこの設問で問われている内容ですね｡

RC〜RFがRA,RB両方に接続可能な状態になっているため､どちらかから受けた情報をもう一方に転送しないためには､｢ｸｴﾘ(あるﾙｰﾄについての情報提供要求)｣をｽﾎﾟｰｸ側から要求されないようにする必要があるので､stubとするわけです｡


設問のﾄﾎﾟﾛｼﾞに似た環境を作ってRBの情報を見てみました｡
(わざとｽﾎﾟｰｸ側がﾙｰﾃｨﾝｸﾞﾃｰﾌﾞﾙに乗るようにしてます)
[code]
RB#sh ip ro
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.200.0/24 is directly connected, Vlan1
D 172.16.0.0/16 is a summary, 00:05:39, Null0
D 172.16.100.0/24 [90/30720] via 172.16.200.14, 00:05:35, Vlan1
[90/30720] via 172.16.200.13, 00:05:35, Vlan1
[90/30720] via 172.16.200.12, 00:05:35, Vlan1
[90/30720] via 172.16.200.11, 00:05:35, Vlan1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.2.1.0/24 is directly connected, FastEthernet0/0
D 10.0.0.0/8 is a summary, 00:05:36, Null0
D 192.168.2.0/24 [90/158720] via 172.16.200.14, 00:05:36, Vlan1
[90/158720] via 172.16.200.13, 00:05:36, Vlan1
[90/158720] via 172.16.200.12, 00:05:36, Vlan1
[90/158720] via 172.16.200.11, 00:05:36, Vlan1
[/code]
もう一つ､ﾄﾎﾟﾛｼﾞﾃｰﾌﾞﾙも
[code]
RB#sh ip eigrp topology

IP-EIGRP Topology Table for AS(1)/ID(172.16.200.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.1.0/24, 1 successors, FD is 281600
via Connected, FastEthernet0/0
P 10.0.0.0/8, 1 successors, FD is 281600
via Summary (281600/0), Null0
P 192.168.2.0/24, 4 successors, FD is 158720
via 172.16.200.11 (158720/156160), Vlan1
via 172.16.200.12 (158720/156160), Vlan1
via 172.16.200.13 (158720/156160), Vlan1
via 172.16.200.14 (158720/156160), Vlan1
via 10.2.1.2 (409600/128256), FastEthernet0/0
P 172.16.200.0/24, 1 successors, FD is 28160
via Connected, Vlan1
P 172.16.0.0/16, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 172.16.100.0/24, 4 successors, FD is 30720
via 172.16.200.11 (30720/28160), Vlan1
via 172.16.200.12 (30720/28160), Vlan1
via 172.16.200.13 (30720/28160), Vlan1
via 172.16.200.14 (30720/28160), Vlan1
[/code]
上記ｻﾝﾌﾟﾙ構成では192.168.2.0/24へのFDが､10.2.1.2(RA)経由よりRC〜RF経由のほうが少ないのでまさに設問通りの状況になってしまっています｡

上記RC〜RFが192.168.2.0/24についての情報を通知しなくなればよいので､回答の通り
[code]eigrp stub[/code]
を設定した後だと
[code]
RB#sh ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(172.16.200.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status

P 10.2.1.0/24, 1 successors, FD is 281600
via Connected, FastEthernet0/0
P 10.0.0.0/8, 1 successors, FD is 281600
via Summary (281600/0), Null0
P 192.168.2.0/24, 1 successors, FD is 158720
via 10.2.1.2 (409600/128256), FastEthernet0/0
P 172.16.200.0/24, 1 successors, FD is 28160
via Connected, Vlan1
P 172.16.0.0/16, 1 successors, FD is 28160
via Summary (28160/0), Null0
P 172.16.100.0/24, 4 successors, FD is 30720
via 172.16.200.11 (30720/28160), Vlan1
via 172.16.200.12 (30720/28160), Vlan1
via 172.16.200.13 (30720/28160), Vlan1
via 172.16.200.14 (30720/28160), Vlan1
[/code]
通知が消えます｡
なのでﾙｰﾃｨﾝｸﾞﾃｰﾌﾞﾙ上も
[code]
RB#sh ip ro
Codes: C - connected, S - static, 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
i - IS-IS, su - IS-IS summary, 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

172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.200.0/24 is directly connected, Vlan1
D 172.16.0.0/16 is a summary, 00:07:40, Null0
D 172.16.100.0/24 [90/30720] via 172.16.200.14, 00:00:09, Vlan1
[90/30720] via 172.16.200.13, 00:00:09, Vlan1
[90/30720] via 172.16.200.12, 00:00:09, Vlan1
[90/30720] via 172.16.200.11, 00:00:09, Vlan1
10.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
C 10.2.1.0/24 is directly connected, FastEthernet0/0
D 10.0.0.0/8 is a summary, 00:07:37, Null0
D 192.168.2.0/24 [90/409600] via 10.2.1.2, 00:00:14, FastEthernet0/0
[/code]
となります｡

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