組播——優選RPF(反向路徑轉發)路由原則驗證


驗證理論

 

 RPF路由選舉規則:

 

 

優選RPF路由原則:

  1. 掩碼最長匹配
  2. 路由最優優先級(Pre值)
  3. 組播靜態路由>MBGP路由>單播路由

 

實驗拓撲

 

 

 

 

 

 

初始配置

配置接口地址以及AR123之間的OSPF

 

初始結果

 

 

 

 

實驗步驟

第一步,配置組播

在全局下開啟組播,在所有接口下配置pim dm

以AR1為例

multicast routing-enable
#
interface Serial1/0/0
link-protocol ppp
ip address 155.1.13.1 255.255.255.0
pim dm
ospf enable 1 area 0.0.0.0
#
interface GigabitEthernet0/0/0
ip address 155.1.12.1 255.255.255.0
pim dm
ospf enable 1 area 0.0.0.0
#
interface GigabitEthernet0/0/1
ip address 10.1.1.254 255.255.255.0
pim dm

 

第二步:

驗證最長掩碼匹配

首先設置組播靜態路由出接口為S1/0/0

[AR3]ip rpf-route-static 10.1.1.0 24 Serial 1/0/0
Info: Succeeded in modifying route.

[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: Serial1/0/0, RPF neighbor: 155.1.13.1
Referenced route/mask: 10.1.1.0/24
Referenced route type: mstatic
Route selection rule: preference-preferred
Load splitting rule: disable

然后增加設置組播靜態路由掩碼增加到25,下一跳到AR2

[AR3]ip rpf-route-static 10.1.1.0 25 155.1.23.2
[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: GigabitEthernet0/0/1, RPF neighbor: 155.1.23.2
Referenced route/mask: 10.1.1.0/25
Referenced route type: mstatic
Route selection rule: preference-preferred
Load splitting rule: disable

此時再查看RPF,下一跳就變更到了AR2上,可見掩碼越長越優先

 

第三步:

驗證路由優先級,優先級越小越優先

首先刪除前面的兩條靜態,然后將10.1.1.0宣告進OSPF,同時在AR2,4之間建立BGP,將10.1.11.0放入BGP中進行傳遞

AR1:

interface GigabitEthernet0/0/1
ip address 10.1.1.254 255.255.255.0
pim dm
ospf enable 1 area 0.0.0.0

bgp 100
peer 150.1.3.3 as-number 100
peer 150.1.3.3 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
undo peer 150.1.3.3 enable
#
ipv4-family multicast
undo synchronization
peer 150.1.3.3 enable

 

AR3:

bgp 100
timer connect-retry 5
peer 150.1.1.1 as-number 100
peer 150.1.1.1 connect-interface LoopBack0
#
ipv4-family unicast
undo synchronization
undo peer 150.1.1.1 enable
#
ipv4-family multicast
undo synchronization
peer 150.1.1.1 enable
#

此時可以看到AR3優選從OSPF學到的,因為OSPF的優先級10比BGP的255更優先

[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: GigabitEthernet0/0/1, RPF neighbor: 155.1.23.2
Referenced route/mask: 10.1.1.0/24
Referenced route type: unicast
Route selection rule: preference-preferred
Load splitting rule: disable

此時注意,通過和BGP比較OSPF的優先級更小,更優先,但是從AR1,2均可通過OSPF學習到10.1.1.0,AR4卻選擇下一跳為AR2,由此可見,相同協議下,度量值越小越優先

[AR3]dis multicast routing-table
Multicast routing table of VPN-Instance: public net
Total 1 entry

00001. (10.1.1.1, 239.1.1.1)
Uptime: 00:00:14
Upstream Interface: GigabitEthernet0/0/1

 

 

第四步:

驗證:組播靜態路由>MBGP路由>單播路由

增加組播靜態路由,在掩碼相同的情況下,將靜態路由,OSPF的優先級都更改為255

[AR3-ospf-1]preference 255

[AR3]ip rpf-route-static  10.1.1.0 24 155.1.13.1 preference 255

此時優選靜態的路由

[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: Serial1/0/0, RPF neighbor: 155.1.13.1
Referenced route/mask: 10.1.1.0/24
Referenced route type: mstatic
Route selection rule: preference-preferred
Load splitting rule: disable

刪除靜態路由之后,此時優選MBGP:

[AR3]UNDO ip rpf-route-static 10.1.1.0 24
[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: GigabitEthernet0/0/1, RPF neighbor: 155.1.23.2
Referenced route/mask: 10.1.1.0/24
Referenced route type: mbgp
Route selection rule: preference-preferred
Load splitting rule: disable

可見,組播靜態路由>MBGP>IGP

 

第五步

驗證通過IGP選舉,開銷相同時選擇下一跳較大IP的鄰居

首先,刪除MBGP

[AR1-bgp-af-multicast]undo network 10.1.1.0 24

然后設置AR3的接口開銷為2

[AR3]dis ip routing-table 10.1.1.0
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Table : Public
Summary Count : 2
Destination/Mask  Proto Pre Cost Flags NextHop Interface

10.1.1.0/24    OSPF 255 3 D 155.1.23.2 GigabitEthernet0/0/1
         OSPF 255 3 D 155.1.13.1 Serial1/0/0

此時負載均衡,但是AR3還是選擇了AR2,因此負載均衡時選擇下一跳較大IP的鄰居

[AR3]dis multicast rpf-info 10.1.1.0
VPN-Instance: public net
RPF information about source: 10.1.1.0
RPF interface: GigabitEthernet0/0/1, RPF neighbor: 155.1.23.2
Referenced route/mask: 10.1.1.0/24
Referenced route type: unicast
Route selection rule: preference-preferred
Load splitting rule: disable
[AR3]

 

第六步,在AR3的0/0/0口上開啟IGMP

[AR3-GigabitEthernet0/0/0]igmp en 

 

 

 

總結

RPF檢測規則:

1.掩碼越長越優先

2.優先級越小越優先(組播靜態優先級默認為1)

3.組播靜態>MBGP>IGP

4.相同IGP開銷越小越優先

5.相同IGP開銷相同,則下一跳IP地址越大越優先


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