思科和H3C关于ISIS重分布路由时关于度量值错误的经验案例
一、 组网:
二、 问题描述:
R1运行OSPF,R2同时OSPF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49,R5属于另一个区域59,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OSPF重发布进ISIS,在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。
三、 过程分析:
R1的配置:
#
ospf 1
area 0.0.0.0
network 1.1.1.1 0.0.0.0
network 10.1.1.0 0.0.0.3
#
R2的配置:
#
isis 1
is-level level-1
network-entity 49.2222.2222.2222.00
import-route ospf 1 cost 63 level-1
#
interface Serial0/2/0
link-protocol ppp
ip address 10.1.1.2 255.255.255.252
#
interface Serial0/2/1
link-protocol ppp
ip address 20.1.1.1 255.255.255.252
isis enable 1
#
ospf 1
area 0.0.0.0
network 10.1.1.0 0.0.0.3
#
R3的配置:
#
isis 1
network-entity 49.3333.3333.3333.00
#
interface Serial0/2/0
link-protocol ppp
ip address 20.1.1.2 255.255.255.252
isis enable 1
#
interface Serial0/2/1
link-protocol ppp
ip address 30.1.1.1 255.255.255.252
isis enable 1
#
R4的配置:
#
isis 1
is-level level-2
network-entity 49.4444.4444.4444.00
#
interface Serial0/2/0
link-protocol ppp
ip address 30.1.1.2 255.255.255.252
isis enable 1
#
interface Serial0/2/1
link-protocol ppp
ip address 40.1.1.1 255.255.255.252
isis enable 1
#
R5的配置:
#
isis 1
is-level level-2
network-entity 59.5555.5555.5555.00
#
interface Serial0/2/0
link-protocol ppp
ip address 40.1.1.2 255.255.255.252
isis enable 1
#
信息显示:
r3上显示的dis ip route
[3]dis ip routing-table
Routing Tables: Public
Destinations : 11 Routes : 11
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.1/32 ISIS 15 137 20.1.1.1 S0/2/0
3.3.3.3/32 Direct 0 0 127.0.0.1 InLoop0
20.1.1.0/30 Direct 0 0 20.1.1.2 S0/2/0
20.1.1.1/32 Direct 0 0 20.1.1.1 S0/2/0
20.1.1.2/32 Direct 0 0 127.0.0.1 InLoop0
30.1.1.0/30 Direct 0 0 30.1.1.1 S0/2/1
30.1.1.1/32 Direct 0 0 127.0.0.1 InLoop0
30.1.1.2/32 Direct 0 0 30.1.1.2 S0/2/1
40.1.1.0/30 ISIS 15 20 30.1.1.2 S0/2/1
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
[3]dis isis route
Route information for ISIS(1)
-----------------------------
ISIS(1) IPv4 Level-1 Forwarding Table
-------------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
--------------------------------------------------------------------------------
20.1.1.0/30 10 NULL S0/2/0 Direct D/L/-
30.1.1.0/30 10 NULL S0/2/1 Direct D/L/-
1.1.1.1/32 10 63 S0/2/0 20.1.1.1 R/L/-
Flags: D-Direct, R-Added to RM, L-Advertised in LSPs, U-Up/Down Bit Set
ISIS(1) IPv4 Level-2 Forwarding Table
-------------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
--------------------------------------------------------------------------------
20.1.1.0/30 10 NULL S0/2/0 Direct D/L/-
30.1.1.0/30 10 NULL S0/2/1 Direct D/L/-
40.1.1.0/30 20 NULL S0/2/1 30.1.1.2 R/-/-
Flags: D-Direct, R-Added to RM, L-Advertised in LSPs, U-Up/Down Bit Set
r4上的信息显示
[4]dis ip routing-table
Routing Tables: Public
Destinations : 11 Routes : 11
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.1/32 ISIS 15 83 30.1.1.1 S0/2/0
4.4.4.4/32 Direct 0 0 127.0.0.1 InLoop0
20.1.1.0/30 ISIS 15 20 30.1.1.1 S0/2/0
30.1.1.0/30 Direct 0 0 30.1.1.2 S0/2/0
30.1.1.1/32 Direct 0 0 30.1.1.1 S0/2/0
30.1.1.2/32 Direct 0 0 127.0.0.1 InLoop0
40.1.1.0/30 Direct 0 0 40.1.1.1 S0/2/1
40.1.1.1/32 Direct 0 0 127.0.0.1 InLoop0
40.1.1.2/32 Direct 0 0 40.1.1.2 S0/2/1
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
[4]dis isis rou
[4]dis isis route
Route information for ISIS(1)
-----------------------------
ISIS(1) IPv4 Level-2 Forwarding Table
-------------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
--------------------------------------------------------------------------------
20.1.1.0/30 20 NULL S0/2/0 30.1.1.1 R/-/-
30.1.1.0/30 10 NULL S0/2/0 Direct D/L/-
40.1.1.0/30 10 NULL S0/2/1 Direct D/L/-
1.1.1.1/32 10 9 S0/2/0 30.1.1.1 R/-/-
Flags: D-Direct, R-Added to RM, L-Advertised in LSPs, U-Up/Down Bit Set
r5上的显示:
[5]dis ip routing-table
Routing Tables: Public
Destinations : 9 Routes : 9
Destination/Mask Proto Pre Cost NextHop Interface
1.1.1.1/32 ISIS 15 93 40.1.1.1 S0/2/0
5.5.5.5/32 Direct 0 0 127.0.0.1 InLoop0
20.1.1.0/30 ISIS 15 30 40.1.1.1 S0/2/0
30.1.1.0/30 ISIS 15 20 40.1.1.1 S0/2/0
40.1.1.0/30 Direct 0 0 40.1.1.2 S0/2/0
40.1.1.1/32 Direct 0 0 40.1.1.1 S0/2/0
40.1.1.2/32 Direct 0 0 127.0.0.1 InLoop0
127.0.0.0/8 Direct 0 0 127.0.0.1 InLoop0
127.0.0.1/32 Direct 0 0 127.0.0.1 InLoop0
[5]dis isis rou
Route information for ISIS(1)
-----------------------------
ISIS(1) IPv4 Level-2 Forwarding Table
-------------------------------------
IPV4 Destination IntCost ExtCost ExitInterface NextHop Flags
--------------------------------------------------------------------------------
20.1.1.0/30 30 NULL S0/2/0 40.1.1.1 R/-/-
30.1.1.0/30 20 NULL S0/2/0 40.1.1.1 R/-/-
40.1.1.0/30 10 NULL S0/2/0 Direct D/L/-
1.1.1.1/32 20 9 S0/2/0 40.1.1.1 R/-/-
Flags: D-Direct, R-Added to RM, L-Advertised in LSPs, U-Up/Down Bit Set
效果表现为,R3收到并加上默认度量,在路由表显示为137,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147的,但是在R4路由表中显示的却也是83,更奇怪的是在R5上面的显示,R5上面显示为93,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。
四、 解决方法:
因为ISIS度量值有两种narrow 与wide,默认情况的度量值会出现选路不精确的问题,默认情况下是narrow。
思科也有同样的问题,不过在重分布时,思科默认是用的internal的方式,所以通过LSP发布路由时路径开销会在配置的cost值的基础上加上0,而H3C默认为external方式,通过LSP发布路由时路径开销会在配置的cost值的基础上加上64.
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