配置ISIS多区域和汇总路由
一、拓扑图：
二、配置和说明：
1、配置各路由器的
IP确保直连链路的能通。指定接口运行的
Level ，以及路由的运行的
Level。图中除了
R5路由运行了
L1其它的都是默认的
L1-2.下面以
R1来为例：
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在路由接口指定发送isis报文类型,标识号我用cisco：
R1(config)#int lo 0
R1(config-if)#ip router isis cisco (
注意是在接口下启用，所以用ip route)
R1(config-if)#isis circuit-type level-1(
特定线路为L1类型，这样发到R2接口S1/0为L1，但是我们却要把S1/0接口指定为L2，所以我们看一下R2收到的路由会全为L2类型)
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R2#show ip route
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, 8 subnets, 2 masks
i L2 172.16.128.0/24 [115/40] via 172.16.255.6, Serial1/1
i L2 172.16.129.0/24 [115/40] via 172.16.255.6, Serial1/1
C 172.16.255.0/30 is directly connected, Serial1/0
C 172.16.255.4/30 is directly connected, Serial1/1
i L2 172.16.255.8/30 [115/20] via 172.16.255.6, Serial1/1
i L2 172.16.255.12/30 [115/30] via 172.16.255.6, Serial1/1
i L2 172.16.1.0/24 [115/20] via 172.16.255.1, Serial1/0
i L2 172.16.2.0/24 [115/20] via 172.16.255.1, Serial1/0
R2#
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但是查看R1的链路数据库会有L1因为Loopback接口为L1，而路由表显示的是直连的，链路数据拓扑会显示L1和L2。）
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R1#show isis database
Area cisco:
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R1.00-00 * 0x0000000E 0x2CFF 1165 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R1.00-00 * 0x00000010 0x3AFC 877 0/0/0
R2.00-00 0x00000007 0x194D 1095 0/0/0
R3.00-00 0x00000008 0xD183 335 0/0/0
R4.00-00 0x0000000D 0xB1FE 599 0/0/0
Area cisco1:
R1#
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R2也将会有
L1和
L2两张表，因为
S1/1接口是
L1-2类型，会有
L1的报文过来：
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R2#sh isis database
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R2.00-00 * 0x00000007 0xF068 415 1/0/0
R3.00-00 0x00000009 0xD77D 1182 1/0/0
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R1.00-00 0x00000010 0x3AFC 846 0/0/0
R2.00-00 * 0x00000007 0x194D 1068 0/0/0
R3.00-00 0x00000008 0xD183 308 0/0/0
R4.00-00 0x0000000D 0xB1FE 572 0/0/0
R2#
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2、下面再来看一下
R5的路由，发现有一条默认路由，其原因是：
R5的路由类型为
L1，它处于
Area 49.0003.而
R4是
L1-2类型，因此其会接到
R4路由器发送的
L1类型的默认路由。这有点像
ospf 中的完全末节区域。这样做的好处就是减少了路由表的大小。同时也增强了
isis 的稳定性。
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R5#show ip route
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 172.16.255.13 to network 0.0.0.0
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
C 172.16.128.0/24 is directly connected, Loopback0
C 172.16.129.0/24 is directly connected, Loopback1
C 172.16.255.12/30 is directly connected, Serial1/0
i*L1 0.0.0.0/0 [115/10] via 172.16.255.13, Serial1/0
R5#
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3、
R5只会有
L1类型的，因为它路由的本身就是
L1，它自己学到的也是
R4发送的
L1类型的默认路由：
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R5#show isis database
IS-IS Level-1 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
R4.00-00 0x0000000D 0xD764 400 1/0/0
R5.00-00 * 0x0000000C 0x55D1 983 0/0/0
R5#
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4、为了能够更有效的减小路由表的大小，还可以配置
IS-IS的汇总。首先查看
R4的路由表，
R4有全网的路由，呵呵。有点像
ospf 中的
ABR。
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R4#show ip route
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, 8 subnets, 2 masks
i L1 172.16.128.0/24 [115/20] via 172.16.255.14, Serial1/1
i L1 172.16.129.0/24 [115/20] via 172.16.255.14, Serial1/1
i L2 172.16.255.0/30 [115/30] via 172.16.255.9, Serial1/0
i L2 172.16.255.4/30 [115/20] via 172.16.255.9, Serial1/0
C 172.16.255.8/30 is directly connected, Serial1/0
C 172.16.255.12/30 is directly connected, Serial1/1
i L2 172.16.1.0/24 [115/40] via 172.16.255.9, Serial1/0
i L2 172.16.2.0/24 [115/40] via 172.16.255.9, Serial1/0
R4#
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5．我要把
R1的两条
loopback 地址汇总一条，让
R4 路由表中
L2类型的：
172.16.1.0/24 和
172.16.2.0/24合并为一条：
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R1(config)#router isis cisco
R1(config-router)#summary-address 172.16.0.0 255.255.252.0
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再次查看一下
R4的路由表
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R4#show ip route
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, 7 subnets, 3 masks
i L1 172.16.128.0/24 [115/20] via 172.16.255.14, Serial1/1
i L1 172.16.129.0/24 [115/20] via 172.16.255.14, Serial1/1
i L2 172.16.255.0/30 [115/30] via 172.16.255.9, Serial1/0
i L2 172.16.255.4/30 [115/20] via 172.16.255.9, Serial1/0
C 172.16.255.8/30 is directly connected, Serial1/0
C 172.16.255.12/30 is directly connected, Serial1/1
i L2 172.16.0.0/22 [115/40] via 172.16.255.9, Serial1/0
R4#
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合并为
172.16.0.0/22 一条路由了。这样我们可以利用汇总路由来精简路由表，有效地提高路由器的稳定性。