实验：配置路由反射器
1. 实验目的
- 熟悉路由反射器的应用场景
- 掌握路由反射器的配置方法
2. 实验拓扑
实验拓扑如图所示：
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3. 实验步骤
（1） 配置IP地址
R1的配置
<Huawei>system-view
Enter system view, return user view with Ctrl+Z.
[Huawei]undo info-center enable
[Huawei]sysname R1
[R1]interface g0/0/0
[R1-GigabitEthernet0/0/0]ip address 12.1.1.1 24
[R1-GigabitEthernet0/0/0]quit
[R1]interface LoopBack 0
[R1-LoopBack0]ip address 1.1.1.1 32
[R1-LoopBack0]quit
R2的配置
<Huawei>system-view
Enter system view, return user view with Ctrl+Z.
[Huawei]undo info-center enable
[Huawei]sysname R2
[R2]interface g0/0/1
[R2-GigabitEthernet0/0/1]ip address 12.1.1.2 24
[R2-GigabitEthernet0/0/1]quit
[R2]interface g0/0/0
[R2-GigabitEthernet0/0/0]ip address 23.1.1.2 24
[R2-GigabitEthernet0/0/0]quit
[R2]interface LoopBack 0
[R2-LoopBack0]ip address 2.2.2.2 32
[R2-LoopBack0]quit
R3的配置
<Huawei>system-view
Enter system view, return user view with Ctrl+Z.
[Huawei]undo info-center enable
Info: Information center is disabled.
[Huawei]sysname R3
[R3]interface g0/0/1
[R3-GigabitEthernet0/0/1]ip address 23.1.1.3 24
[R3-GigabitEthernet0/0/1]quit
[R3]interface g0/0/0
[R3-GigabitEthernet0/0/0]ip address 34.1.1.3 24
[R3-GigabitEthernet0/0/0]quit
[R3]interface LoopBack 0
[R3-LoopBack0]ip address 3.3.3.3 32
[R3-LoopBack0]quit
R4的配置
<Huawei>system-view
Enter system view, return user view with Ctrl+Z.
[Huawei]undo info-center enable
Info: Information center is disabled.
[Huawei]sysname R4
[R4]interface g0/0/1
[R4-GigabitEthernet0/0/1]ip address 34.1.1.4 24
[R4-GigabitEthernet0/0/1]quit
[R4]interface LoopBack 0
[R4-LoopBack0]ip address 4.4.4.4 32
[R4-LoopBack0]quit
（2）配置IGP
R2的配置
[R2]ospf router-id 2.2.2.2
[R2-ospf-1]area 0
[R2-ospf-1-area-0.0.0.0]network 2.2.2.2 0.0.0.0
[R2-ospf-1-area-0.0.0.0]network 23.1.1.10 0.0.0.255
[R2-ospf-1-area-0.0.0.0]quit
R3的配置
[R3]ospf router-id 3.3.3.3
[R3-ospf-1]area 0
[R3-ospf-1-area-0.0.0.0]network 23.1.1.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]network 34.1.1.0 0.0.0.255
[R3-ospf-1-area-0.0.0.0]network 3.3.3.3 0.0.0.0
[R3-ospf-1-area-0.0.0.0]quit
R4的配置
[R4]ospf router-id 4.4.4.4
[R4-ospf-1]area 0
[R4-ospf-1-area-0.0.0.0]network 4.4.4.4 0.0.0.0
[R4-ospf-1-area-0.0.0.0]network 34.1.1.0 0.0.0.255
[R4-ospf-1-area-0.0.0.0]quit
- 配置BGP R1与R2建立EBGP的邻居关系，R2与R3、R3与R4为IBGP的邻居关系。
R1的配置
[R1]bgp 100
[R1-bgp]router-id 1.1.1.1
[R1-bgp]peer 12.1.1.2 as-number 200
[R1-bgp]quit
R2的配置
[R2]bgp 200
[R2-bgp]router-id 2.2.2.2
[R2-bgp]peer 12.1.1.1 as-number 100
[R2-bgp]peer 3.3.3.3 as-number 200
[R2-bgp]peer 3.3.3.3 connect-interface LoopBack 0
[R2-bgp]peer 3.3.3.3 next-hop-local
[R2-bgp]quit
R3的配置
[R3]bgp 200
[R3-bgp]router-id 3.3.3.3
[R3-bgp]peer 2.2.2.2 as-number 200
[R3-bgp]peer 2.2.2.2 connect-interface LoopBack 0
[R3-bgp]peer 4.4.4.4 as-number 200
[R3-bgp]peer 4.4.4.4 connect-interface LoopBack 0
[R3-bgp]quit
R4的配置
[R4]bgp 200
[R4-bgp]router-id 4.4.4.4
[R4-bgp]peer 3.3.3.3 as-number 200
-
- 实验调试
- 在R1上宣告1.1.1.1/32的路由
[R1]bgp 100
[R1-bgp]network 1.1.1.1 32
[R1-bgp]quit
- 在R3上查看路由表
[R3]display bgp routing-table
BGP Local router ID is 3.3.3.3
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplet
Total Number of Routes: 1
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 1.1.1.1/32 2.2.2.2 0 100 0 100i
通过以上输出，可以看到1.1.1.1是最优的，但是我们在R4上是看不到1.1.1.1这条路由
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- 在R3上查看BGP详细路由表，看它是否传递给了R4
[R3]display bgp peer 4.4.4.4 verbose //显示BGP对等体的详细信息。
BGP Peer is 4.4.4.4, remote AS 200
Type: IBGP link
BGP version 4, Remote router ID 4.4.4.4
Update-group ID: 1
BGP current state: Established, Up for 00h41m07s
BGP current event: RecvKeepalive
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Advertised total routes: 0
Port: Local - 65228 Remote - 179
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 43 messages
Update messages 0
Open messages 1
KeepAlive messages 42
Notification messages 0
Refresh messages 0
Sent: Total 44 messages
Update messages 0
Open messages 2
KeepAlive messages 42
Notification messages 0
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2022-05-31 13:04:21-08:00
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
Connect-interface has been configured
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured
通过以上输出，可以看到R3没有把路由传给R4，这是由于BGP水平分割的问题
【技术要点】
BGP水平分割：BGP路由器，从IBGP邻居收到一条路由，不会传给它的其它IBGP邻居
- 将R3配置为路由反射器，指定R4为它的客户端
[R3]bgp 200
[R3-bgp]peer 4.4.4.4 reflect-client
[R3-bgp]quit
- 在R3上查看RR
[R3]display bgp peer 4.4.4.4 verbose
BGP Peer is 4.4.4.4, remote AS 200
Type: IBGP link
BGP version 4, Remote router ID 4.4.4.4
Update-group ID: 0
BGP current state: Established, Up for 00h49m17s
BGP current event: RecvKeepalive
BGP last state: OpenConfirm
BGP Peer Up count: 1
Received total routes: 0
Received active routes total: 0
Advertised total routes: 1
Port: Local - 65228 Remote - 179
Configured: Connect-retry Time: 32 sec
Configured: Active Hold Time: 180 sec Keepalive Time:60 sec
Received : Active Hold Time: 180 sec
Negotiated: Active Hold Time: 180 sec Keepalive Time:60 sec
Peer optional capabilities:
Peer supports bgp multi-protocol extension
Peer supports bgp route refresh capability
Peer supports bgp 4-byte-as capability
Address family IPv4 Unicast: advertised and received
Received: Total 51 messages
Update messages 0
Open messages 1
KeepAlive messages 50
Notification messages 0
Refresh messages 0
Sent: Total 53 messages
Update messages 1
Open messages 2
KeepAlive messages 50
Notification messages 0
Refresh messages 0
Authentication type configured: None
Last keepalive received: 2022-05-31 13:12:21-08:00
Minimum route advertisement interval is 15 seconds
Optional capabilities:
Route refresh capability has been enabled
4-byte-as capability has been enabled
It's route-reflector-client
Connect-interface has been configured
Peer Preferred Value: 0
Routing policy configured:
No routing policy is configured
通过以上输出可以看到R4为RR的客户端
- 在R4上查看路由表
<R4>display bgp routing-table
BGP Local router ID is 4.4.4.4
Status codes: * - valid, > - best, d - damped,
h - history, i - internal, s - suppressed, S - Stale
Origin : i - IGP, e - EGP, ? - incomplete
Total Number of Routes: 1
Network NextHop MED LocPrf PrefVal Path/Ogn
*>i 1.1.1.1/32 2.2.2.2 0 100 0 100i
通过以上输出可以看到R4的BGP路由表里有1.1.1.1了
- 查看起源ID和cluster list
<R4>display bgp routing-table 1.1.1.1
BGP local router ID : 4.4.4.4
Local AS number : 200
Paths: 1 available, 1 best, 1 select
BGP routing table entry information of 1.1.1.1/32:
From: 3.3.3.3 (3.3.3.3)
Route Duration: 00h06m33s
Relay IP Nexthop: 34.1.1.3
Relay IP Out-Interface: GigabitEthernet0/0/1
Original nexthop: 2.2.2.2
Qos information : 0x0
AS-path 100, origin igp, MED 0, localpref 100, pref-val 0, valid, internal, best, select, active, pre 255, IGP cost 2
Originator: 2.2.2.2 //本地AS中通告该路由的BGP路由器Router ID，存在多个RR也不会改变，防环
Cluster list: 3.3.3.3 //当RR收到一条携带Cluster_list属性的BGP路由，且该属性值中包含该簇的Cluster_ID时，RR认为该条路由存在环路，因此将忽略关于该条路由的更新。
【技术要点】Cluster_List属性
路由反射器和它的客户机组成一个集群（Cluster），使用AS内唯一的Cluster ID作为标识。为了防止集群间产生路由环路，路由反射器使用Cluster_List属性，记录路由经过的所有集群的Cluster ID。
- 当一条路由第一次被RR反射的时候，RR会把本地Cluster ID添加到Cluster List的前面。如果没有Cluster_List属性，RR就创建一个。
- 当RR接收到一条更新路由时，RR会检查Cluster List。如果Cluster List中已经有本地Cluster ID，丢弃该路由；如果没有本地Cluster ID，将其加入Cluster List，然后反射该更新路由。
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