ISIS重分布度量问题
概述：
将RIP重发布到ISIS，默认情况下一切正常，度量值也会累加，可是后来重发布的时候改变了种子度量值为63（重发布时最大可选数），发布等级为Level-1就发现不正常了。
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拓扑：
配置：
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R1的配置：
R1#show run
Building configuration...
Building configuration...
Current configuration : 744 bytes
!
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface Serial1/0
no ip address
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 192.1.1.1 255.255.255.0
serial restart-delay 0
!
router rip
version 1
network 1.0.0.0
network 192.1.1.0
!
end
!
interface Loopback0
ip address 1.1.1.1 255.255.255.0
!
interface Serial1/0
no ip address
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 192.1.1.1 255.255.255.0
serial restart-delay 0
!
router rip
version 1
network 1.0.0.0
network 192.1.1.0
!
end
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R2的配置：
R2#show run
Building configuration...
Building configuration...
Current configuration : 833 bytes
!
interface Serial1/0
ip address 192.1.1.2 255.255.255.0
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 172.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-1
!
router isis
net 49.0001.0002.0002.0002.00
is-type level-1
redistribute rip level-1
!
router rip
network 172.1.0.0
network 192.1.1.0
!
end
!
interface Serial1/0
ip address 192.1.1.2 255.255.255.0
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 172.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-1
!
router isis
net 49.0001.0002.0002.0002.00
is-type level-1
redistribute rip level-1
!
router rip
network 172.1.0.0
network 192.1.1.0
!
end
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R3的配置：
R3#show run
Building configuration...
Building configuration...
Current configuration : 788 bytes
!
interface Serial1/0
ip address 172.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-1
!
interface Serial2/0
ip address 202.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-2-only
!
router isis
net 49.0001.0003.0003.0003.00
!
end
!
interface Serial1/0
ip address 172.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-1
!
interface Serial2/0
ip address 202.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-2-only
!
router isis
net 49.0001.0003.0003.0003.00
!
end
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R4的配置：
R4#show run
Building configuration...
Building configuration...
Current configuration : 814 bytes
!
interface Serial1/0
ip address 202.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-2-only
!
interface Serial2/0
ip address 10.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-2-only
!
router isis
net 49.0001.0004.0004.0004.00
is-type level-2-only
!
end
!
interface Serial1/0
ip address 202.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-2-only
!
interface Serial2/0
ip address 10.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-2-only
!
router isis
net 49.0001.0004.0004.0004.00
is-type level-2-only
!
end
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R5的配置：
R5#show run
Building configuration...
!
interface Serial1/0
ip address 10.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-2-only
!
interface Serial2/0
no ip address
serial restart-delay 0
!
router isis
net 49.0002.0005.0005.0005.00
is-type level-2-only
!
end
Building configuration...
!
interface Serial1/0
ip address 10.1.1.2 255.255.255.0
ip router isis
serial restart-delay 0
clock rate 64000
isis circuit-type level-2-only
!
interface Serial2/0
no ip address
serial restart-delay 0
!
router isis
net 49.0002.0005.0005.0005.00
is-type level-2-only
!
end
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R1运行rip，R2同时RIP与IS-IS，R2并且被配置成为level-1，R3运行ISIS，配置为level-1-2。R4运行ISIS配置为level-2。R5运行ISIS配置为leve-2。其中R2，R3，R4属于同一个区域0001。R5属于另一个区域0002。所有路由器的接口运行的isis等级也都按如上配置进行优化。并且在R2上面进行将RIP重发布进ISIS，在默认情况下一切正常。
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现象：
下面我们分别来看一下R3，R4，R5关于1.0.0.0的度量值
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R3#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 10, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:18:37 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 10, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 10, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:18:37 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 10, traffic share count is 1
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R4#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 20, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:19:45 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 20, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 20, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:19:45 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 20, traffic share count is 1
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R5#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 30, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:20:13 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 30, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 30, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:20:13 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 30, traffic share count is 1
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关于1.0.0.0的路由条目，R2重发布进ISIS默认度量值为0，收到此条目加上自身默认度量，放进路由表度量显示为10，R4显示20，R5显示30。这种现象表明，在默认情况下度量值确实是累加。 并且，如果将R5设置成为与R2，R3，R4为同一区域时，效果依然存在，那么就说明度量的累加与区域无关。
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现在我在R2上面重发布时将度量值改变为63
R2#show run
Building configuration...
Building configuration...
Current configuration : 843 bytes
!
interface Serial1/0
ip address 192.1.1.2 255.255.255.0
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 172.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-1
!
router isis
net 49.0001.0002.0002.0002.00
is-type level-1
redistribute rip metric 63 level-1
!
router rip
network 172.1.0.0
network 192.1.1.0
!
interface Serial1/0
ip address 192.1.1.2 255.255.255.0
serial restart-delay 0
clock rate 64000
!
interface Serial2/0
ip address 172.1.1.1 255.255.255.0
ip router isis
serial restart-delay 0
isis circuit-type level-1
!
router isis
net 49.0001.0002.0002.0002.00
is-type level-1
redistribute rip metric 63 level-1
!
router rip
network 172.1.0.0
network 192.1.1.0
!
end
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现在我们再来看看R3，R4，R5关于1.0.0.0的度量值有何变化
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R3#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 73, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:02:19 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 73, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 73, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:02:19 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 73, traffic share count is 1
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R4#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 73, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:02:45 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 73, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 73, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:02:45 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 73, traffic share count is 1
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R5#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 83, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:03:01 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 83, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 83, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:03:01 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 83, traffic share count is 1
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效果表现为，R3收到并加上默认度量，在路由表显示为73，R3看上去比较正常，现在看看R4，默认情况下他也是累加的，推测应该是83的。但是在R4路由表中显示的却也是73。奇怪，更奇怪的是在R5上面的显示，R5上面显示为83，表现出了累加。。不管R5是否与R2，R3，R4在不在同一区域，其效果依然一样。
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现在我在重发布时将种子度量配置为20，看看R3，R4，R5关于1.0.0.0的度量又会是什么样
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R3#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 30, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:00:10 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 30, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 30, type level-1
Redistributing via isis
Last update from 172.1.1.1 on Serial1/0, 00:00:10 ago
Routing Descriptor Blocks:
* 172.1.1.1, from 172.1.1.1, via Serial1/0
Route metric is 30, traffic share count is 1
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R4#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 40, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:00:29 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 40, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 40, type level-2
Redistributing via isis
Last update from 202.1.1.1 on Serial1/0, 00:00:29 ago
Routing Descriptor Blocks:
* 202.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 40, traffic share count is 1
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R5#show ip route 1.0.0.0
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 50, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:00:58 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 50, traffic share count is 1
Routing entry for 1.0.0.0/8
Known via "isis", distance 115, metric 50, type level-2
Redistributing via isis
Last update from 10.1.1.1 on Serial1/0, 00:00:58 ago
Routing Descriptor Blocks:
* 10.1.1.1, from 202.1.1.1, via Serial1/0
Route metric is 50, traffic share count is 1
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R3表现为30，R4表现为40，R5表现50。进行了累加。并且在不断的调整种子度量时发现在度量值在累加过程中有一个限度那就是73。在73这里总要停留一下，并且与区域无关。
例如，我现在重发布时种子度量为62，那么在R3表现为72，R4上表现为73，R5上面表现为83
找了一下资料，发现ISIS度量值有两种narrow 与wide，资料上说默认情况的度量值会出现选路不精确的问题。所以定义了另一种度量值。默认情况下是narrow。
问题解决
在所有运行ISIS的路由器的路由进程模式下输入命令Router(config-router)#metric-style wide以上全部问题解决，所有度量值表现为累加，并且没有73这个界限。