4 MPLS-配置
4.1 MPLS基本配置
4.1.1 必要配置
- 每台路由器开启CEF交换,命令全局模式下IP CEF;
- 每个接口激活标签交换和默认激活LDP,命令接口下MPLS IP ;
可以修改是否激活哪个协议,而不是默认的LDP协议
4.1.2 可选配置
- 配MPLS-ID,否则的话会自己选ROUTER-ID,建议配置为LOOPBACK接口地址;
- TTL配置,默认开始,可以关闭
- 条件通告
MPLS分发模式,如不想通告某个路由的标签。
4.1.3 查看及验证
4.2 MPLS基础实验
配置顺序:
- 接口配置
- 运行IGP(OSPF)
- 配置LDP ROUTERID,设定标签范围
- 接口激活MPLS及LDP
4.2.1 基础配置
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 10.1.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config)#interface loopback 0
R1(config-if)#ip address 1.1.1.1 255.255.255.255
R1(config-if)#no shutdown
R1(config)#router ospf 1
R1(config-router)#network 10.1.12.1 0.0.0.0 area 0
R1(config-router)#network 1.1.1.1 255.255.255.255 area 0
R1(config)#mpls ldp router-id loopback 0
R1(config)#mpls label range 100 199
R1(config)#interface fastEthernet 0/0
R1(config-if)#mpls ip
R2(config)#interface fastEthernet 0/0
R2(config-if)#ip address 10.1.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface fastEthernet 1/0
R2(config-if)#ip address 10.1.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface loopback 0
R2(config-if)#ip address 2.2.2.2 255.255.255.255
R2(config-if)#no shutdown
R2(config)#router ospf 1
R2(config-router)#router-id 2.2.2.2
R2(config-router)#network 10.1.12.2 0.0.0.0 area 0
R2(config-router)#network 10.1.23.2 0.0.0.0 area 0
R2(config-router)#network 2.2.2.2 255.255.255.255 area 0
R2(config)#mpls ldp router-id loopback 0
R2(config)#mpls label range 200 299
R2(config)#interface fastEthernet 0/0
R2(config-if)#mpls ip
R2(config)#interface fastEthernet 1/0
R2(config-if)#mpls ip
R3(config)#interface fastEthernet 1/0
R3(config-if)#ip address 10.1.23.3 255.255.255.0
R3(config-if)#no shutdown
R3(config)#interface fastEthernet 0/0
R3(config-if)#ip address 10.1.34.3 255.255.255.0
R3(config-if)#no shutdown
R3(config)#interface loopback 0
R3(config-if)#ip address 3.3.3.3 255.255.255.255
R3(config-if)#no shutdown
R3(config)#router ospf 1
R3(config-router)#router-id 3.3.3.3
R3(config-router)#network 10.1.23.3 0.0.0.0 area 0
R3(config-router)#network 10.1.34.3 0.0.0.0 area 0
R3(config-router)#network 3.3.3.3 255.255.255.255 area 0
R3(config)#mpls ldp router-id loopback 0
R3(config)#mpls label range 300 399
R3(config)#interface fastEthernet 1/0
R3(config-if)#mpls ip
R3(config)#interface fastEthernet 0/0
R3(config-if)#mpls ip
R4(config)#interface fastEthernet 0/0
R4(config-if)#ip address 10.1.34.4 255.255.255.0
R4(config-if)#no shutdown
R4(config)#interface loopback 0
R4(config-if)#ip address 4.4.4.4 255.255.255.0
R4(config-if)#no shutdown
R4(config)#router ospf 1
R4(config-router)#router-id 4.4.4.4
R4(config-router)#network 10.1.34.4 0.0.0.0 area 0
R4(config-router)#network 4.4.4.4 255.255.255.255 area 0
R4(config)#mpls ldp router-id loopback 0
R4(config)#mpls label range 400 499
R4(config)#interface fastEthernet 0/0
R4(config-if)#mpls ip
4.2.2 查看基础信息
R1#show mpls ldp discovery
Local LDP Identifier:
1.1.1.1:0
Discovery Sources:
Interfaces:
FastEthernet0/0 (ldp): xmit/recv
LDP Id: 2.2.2.2:0
查看R1的邻居,显示为R2
R1#show mpls ldp neighbor
Peer LDP Ident: 2.2.2.2:0; Local LDP Ident 1.1.1.1:0
TCP connection: 2.2.2.2.59285 - 1.1.1.1.646
State: Oper; Msgs sent/rcvd: 14/15; Downstream
Up time: 00:04:14
LDP discovery sources:
FastEthernet0/0, Src IP addr: 10.1.12.2
Addresses bound to peer LDP Ident:
10.1.12.2 2.2.2.2 10.1.23.2
查看邻居是否启动,显示对方为2.2.2.2
R2#show mpls ldp neighbor
Peer LDP Ident: 1.1.1.1:0; Local LDP Ident 2.2.2.2:0
TCP connection: 1.1.1.1.646 - 2.2.2.2.59285
State: Oper; Msgs sent/rcvd: 16/15; Downstream
Up time: 00:05:00
LDP discovery sources:
FastEthernet0/0, Src IP addr: 10.1.12.1
Addresses bound to peer LDP Ident:
10.1.12.1 1.1.1.1
Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 2.2.2.2:0
TCP connection: 3.3.3.3.23559 - 2.2.2.2.646
State: Oper; Msgs sent/rcvd: 12/12; Downstream
Up time: 00:02:11
LDP discovery sources:
FastEthernet1/0, Src IP addr: 10.1.23.3
Addresses bound to peer LDP Ident:
3.3.3.3 10.1.34.3 10.1.23.3
R2有两个邻居,一个是1.1.1.1,一个为3.3.3.3
R2#show mpls ldp parameters
Protocol version: 1
Session hold time: 180 sec; keep alive interval: 60 sec
Discovery hello: holdtime: 15 sec; interval: 5 sec
Discovery targeted hello: holdtime: 90 sec; interval: 10 sec
Downstream on Demand max hop count: 255
Downstream on Demand Path Vector Limit: 255
LDP for targeted sessions
LDP initial/maximum backoff: 15/120 sec
LDP loop detection: off
查看LDP参数
4.2.3 查看信息表
R1#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
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.12.2, 00:25:41, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/3] via 10.1.12.2, 00:22:52, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/4] via 10.1.12.2, 00:22:52, FastEthernet0/0
10.0.0.0/24 is subnetted, 3 subnets
C 10.1.12.0 is directly connected, FastEthernet0/0
O 10.1.23.0 [110/2] via 10.1.12.2, 00:25:06, FastEthernet0/0
O 10.1.34.0 [110/3] via 10.1.12.2, 00:22:52, FastEthernet0/0
查看RIB表
R1#show mpls ldp bindings
lib entry: 1.1.1.1/32, rev 4
local binding: label: imp-null
remote binding: lsr: 2.2.2.2:0, label: 200
lib entry: 2.2.2.2/32, rev 6
local binding: label: 100
remote binding: lsr: 2.2.2.2:0, label: imp-null
lib entry: 3.3.3.3/32, rev 12
local binding: label: 103
remote binding: lsr: 2.2.2.2:0, label: 202
lib entry: 4.4.4.4/32, rev 10
local binding: label: 102
remote binding: lsr: 2.2.2.2:0, label: 201
lib entry: 10.1.12.0/24, rev 2
local binding: label: imp-null
remote binding: lsr: 2.2.2.2:0, label: imp-null
lib entry: 10.1.23.0/24, rev 8
local binding: label: 101
remote binding: lsr: 2.2.2.2:0, label: imp-null
lib entry: 10.1.34.0/24, rev 14
local binding: label: 104
remote binding: lsr: 2.2.2.2:0, label: 203
查看LIB表:
对于1.1.1.1的路由:
本地捆绑的标签为为IMP-NULL,因为直连且PHP,为自己直连路由分配的便签为IMP-NULL;
从R2学到的关于1.1.1.1的路由捆绑的标签为200;
对于2.2.2.2的路由:
本地捆绑的标签值为100;
从R2传过来的标签为IMP-NULL,因为是R2本地直连的路由;
对于3.3.3.3的路由:
本地捆绑的标签值为103;
从R2传过来的标签为202;
R1#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
100 Pop Label 2.2.2.2/32 0 Fa0/0 10.1.12.2
101 Pop Label 10.1.23.0/24 0 Fa0/0 10.1.12.2
102 201 4.4.4.4/32 0 Fa0/0 10.1.12.2
103 202 3.3.3.3/32 0 Fa0/0 10.1.12.2
104 203 10.1.34.0/24 0 Fa0/0 10.1.12.2
查看LFIB表
LOCAL:本地R1为路由前缀捆绑给的标签
OUTGOING:下一跳提供的
NEXT HOP:从LIB或者FIB来的
R1#show ip cef
Prefix Next Hop Interface
0.0.0.0/0 no route
0.0.0.0/8 drop
0.0.0.0/32 receive
1.1.1.1/32 receive Loopback0
2.2.2.2/32 10.1.12.2 FastEthernet0/0
3.3.3.3/32 10.1.12.2 FastEthernet0/0
4.4.4.4/32 10.1.12.2 FastEthernet0/0
10.1.12.0/24 attached FastEthernet0/0
10.1.12.0/32 receive FastEthernet0/0
10.1.12.1/32 receive FastEthernet0/0
10.1.12.2/32 attached FastEthernet0/0
10.1.12.255/32 receive FastEthernet0/0
10.1.23.0/24 10.1.12.2 FastEthernet0/0
10.1.34.0/24 10.1.12.2 FastEthernet0/0
127.0.0.0/8 drop
224.0.0.0/4 drop
224.0.0.0/24 receive
240.0.0.0/4 drop
255.255.255.255/32 receive
查看FIB表,指示下一跳和出接口
4.2.3.1 控制层流程
以4.4.4.4路由为例,R1R2R3都有R4的路由。
R4#show mpls ldp binding
lib entry: 4.4.4.0/24, rev 4
local binding: label: imp-null
lib entry: 4.4.4.4/32, rev 8
remote binding: lsr: 3.3.3.3:0, label: 300
R4本地绑定4.4.4.4路由便签为IMP-NULL,R4从R3学到的路由压入标签为300
R3#show mpls ldp bindings
lib entry: 4.4.4.0/24, rev 9
remote binding: lsr: 4.4.4.4:0, label: imp-null
lib entry: 4.4.4.4/32, rev 8
local binding: label: 300
remote binding: lsr: 2.2.2.2:0, label: 201
R3本地绑定4.4.4.4路由便签为300,从R2学到的4.4.4.4的标签为201,从R4学到的为IMP-NULL
R2#show mpls ldp bindings
R2#show mpls ldp bindings
lib entry: 4.4.4.4/32, rev 10
local binding: label: 201
remote binding: lsr: 3.3.3.3:0, label: 300
remote binding: lsr: 1.1.1.1:0, label: 102
R2本地绑定4.4.4.4路由便签为201,从R3学到的标签为300,从R1学到的标签为102
R1#show mpls ldp bindings
lib entry: 4.4.4.4/32, rev 10
local binding: label: 102
remote binding: lsr: 2.2.2.2:0, label: 201
R1本地绑定4.4.4.4路由便签为102,从R2学到的为201
即R4本地绑定IMP-NULL给R3,R3绑定300给R2,R2绑定201给R1,R1本地绑定102
4.2.3.2 数据层流程
R1发出IP数据包到4.4.4.4
由于R1始发,如PING,初始为IP包,查CEF表即FIB表。
R1#show ip cef
Prefix Next Hop Interface
0.0.0.0/0 no route
0.0.0.0/8 drop
0.0.0.0/32 receive
1.1.1.1/32 receive Loopback0
2.2.2.2/32 10.1.12.2 FastEthernet0/0
3.3.3.3/32 10.1.12.2 FastEthernet0/0
4.4.4.4/32 10.1.12.2 FastEthernet0/0
10.1.12.0/24 attached FastEthernet0/0
10.1.12.0/32 receive FastEthernet0/0
10.1.12.1/32 receive FastEthernet0/0
10.1.12.2/32 attached FastEthernet0/0
10.1.12.255/32 receive FastEthernet0/0
10.1.23.0/24 10.1.12.2 FastEthernet0/0
10.1.34.0/24 10.1.12.2 FastEthernet0/0
127.0.0.0/8 drop
224.0.0.0/4 drop
224.0.0.0/24 receive
240.0.0.0/4 drop
255.255.255.255/32 receive
R1#show ip cef 4.4.4.4 detail
4.4.4.4/32, epoch 0
local label info: global/102
nexthop 10.1.12.2 FastEthernet0/0 label 201
查看明细表,显示压入标签201,即控制层面R2位4.4.4.4路由绑定的标签
R2收到压入201的标签包后,查LFIB表
R2#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
200 Pop Label 1.1.1.1/32 0 Fa0/0 10.1.12.1
201 300 4.4.4.4/32 0 Fa1/0 10.1.23.3
202 Pop Label 3.3.3.3/32 0 Fa1/0 10.1.23.3
203 Pop Label 10.1.34.0/24 0 Fa1/0 10.1.23.3
显示4.4.4.4的入栈为201,出栈为300,出口为F1/0,下一跳为10.1.23.3
R2将标签201置换为300,发给R3,R3接着查自己的LFIB表
R3#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
300 No Label 4.4.4.4/32 0 Fa0/0 10.1.34.4
301 Pop Label 2.2.2.2/32 0 Fa1/0 10.1.23.2
302 200 1.1.1.1/32 0 Fa1/0 10.1.23.2
303 Pop Label 10.1.12.0/24 0 Fa1/0 10.1.23.2
显示入栈为300的4.4.4.4的路由,显示NO LABEL,弹掉所有标签,变成IP包发给R4
整体流程:
- R1始发IP,查看CEF即FIB表,压入标签201,发给R2;
- R2查本地LFIB表,R2将标签201置换为300,发给R3;
- R3查本地LFIB表,弹出所有标签,变成IP包发给R4;
4.3 MPLS环境中的BGP
4.3.1 试验1
4.3.1.1 OSPF配置
R1配置
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 10.1.12.1 255.255.255.0
R1(config-if)#no shutdown
R1(config)#interface fastEthernet 1/0
R1(config-if)#ip address 10.1.15.1 255.255.255.0
R1(config-if)#no shutdown
R1(config)#interface loopback 0
R1(config-if)#ip address 1.1.1.1 255.255.255.255
R1(config-if)#no shutdown
R1(config)#router ospf 1
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 10.1.12.1 0.0.0.0 area 0
R1(config-router)#network 10.1.15.1 0.0.0.0 area 0
R1(config-router)#network 1.1.1.1 0.0.0.0 area 0
R2配置
R2(config)#interface fastEthernet 0/0
R2(config-if)#ip address 10.1.12.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface fastEthernet 1/0
R2(config-if)#ip address 10.1.23.2 255.255.255.0
R2(config-if)#no shutdown
R2(config)#interface loopback 0
R2(config-if)#ip address 2.2.2.2 255.255.255.255
R2(config-if)#no shutdown
R2(config)#router ospf 1
R2(config-router)#router-id 2.2.2.2
R2(config-router)#network 10.1.12.2 0.0.0.0 area 0
R2(config-router)#network 10.1.23.2 0.0.0.0 area 0
R2(config-router)#network 2.2.2.2 0.0.0.0 area 0
R3配置
R3(config)#interface fastEthernet 1/0
R3(config-if)#ip address 10.1.23.3 255.255.255.0
R3(config-if)#no shutdown
R3(config)#interface fastEthernet 0/0
R3(config-if)#ip address 10.1.34.3 255.255.255.0
R3(config-if)#no shutdown
R3(config)#interface loopback 0
R3(config-if)#ip address 3.3.3.3 255.255.255.255
R3(config-if)#no shutdown
R3(config)#router ospf 1
R3(config-router)#router-id 3.3.3.3
R3(config-router)#network 10.1.23.3 0.0.0.0 area 0
R3(config-router)#network 10.1.34.3 0.0.0.0 area 0
R3(config-router)#network 3.3.3.3 0.0.0.0 area 0
R4配置
R4(config)#interface fastEthernet 0/0
R4(config-if)#ip address 10.1.34.4 255.255.255.0
R4(config-if)#no shutdown
R4(config)#interface fastEthernet 1/0
R4(config-if)#ip address 10.1.46.4 255.255.255.0
R4(config-if)#no shutdown
R4(config)#interface loopback 0
R4(config-if)#ip address 4.4.4.4 255.255.255.255
R4(config-if)#no shutdown
R4(config)#router ospf 1
R4(config-router)#router-id 4.4.4.4
R4(config-router)#network 10.1.34.4 0.0.0.0 area 0
R4(config-router)#network 10.1.46.4 0.0.0.0 area 0
R4(config-router)#network 4.4.4.4 0.0.0.0 area 0
R5配置,不需要运行OSPF
R5(config)#interface fastEthernet 1/0
R5(config-if)#ip address 10.1.15.5 255.255.255.0
R5(config-if)#no shutdown
R5(config)#interface loopback 0
R5(config-if)#ip address 5.5.5.5 255.255.255.255
R5(config-if)#no shutdown
R5(config-if)#exit
R6配置,不需要运行OSPF
R6(config)#interface fastEthernet 1/0
R6(config)#interface fastEthernet 1/0
R6(config-if)#ip address 10.1.46.6 255.255.255.0
R6(config-if)#no shutdown
R6(config)#interface loopback 0
R6(config-if)#ip address 6.6.6.6 255.255.255.255
R6(config-if)#no shutdown
R1#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
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.12.2, 00:15:43, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/3] via 10.1.12.2, 00:09:46, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/4] via 10.1.12.2, 00:05:33, FastEthernet0/0
10.0.0.0/24 is subnetted, 5 subnets
C 10.1.15.0 is directly connected, FastEthernet1/0
C 10.1.12.0 is directly connected, FastEthernet0/0
O 10.1.23.0 [110/2] via 10.1.12.2, 00:16:03, FastEthernet0/0
O 10.1.46.0 [110/4] via 10.1.12.2, 00:05:33, FastEthernet0/0
O 10.1.34.0 [110/3] via 10.1.12.2, 00:10:00, FastEthernet0/0
R1R2R3R4上路由都有了。
4.3.1.2 运行BGP
R1R4基于IBGP关系,R1R5、R4R6基于EBGP关系
R1(config)#router bgp 1234
R1(config-router)#bgp router-id 1.1.1.1
R1(config-router)#neighbor 10.1.15.5 remote-as 500
R1(config-router)#neighbor 10.1.34.4 remote-as 1234
R4(config)#router bgp 1234
R4(config-router)#bgp router-id 4.4.4.4
R4(config-router)#neighbor 10.1.12.1 remote-as 1234
R4(config-router)#neighbor 10.1.46.6 remote-as 600
R5(config)#router bgp 500
R5(config-router)#bgp router-id 5.5.5.5
R5(config-router)#neighbor 10.1.15.1 remote-as 1234
R6(config)#router bgp 600
R6(config-router)#bgp router-id 6.6.6.6
R6(config-router)#neighbor 10.1.46.4 remote-as 1234
4.3.1.3 测试1:BGP路由黑洞
将5.5.5.5路由放入R5
R5(config)#router bgp 500
R5(config-router)#network 5.5.5.5 mask 255.255.255.255
R1#show ip bgp
BGP table version is 2, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 5.5.5.5/32 10.1.15.5 0 0 500 i
这时R1学到了R5放入的5.5.5.5的路由
R4#show ip bgp
BGP table version is 2, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i5.5.5.5/32 10.1.15.5 0 100 0 500 i
R1会把路由传给R4,R4上也有了5.5.5.5的路由
R6#show ip bgp
BGP table version is 2, local router ID is 6.6.6.6
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 5.5.5.5/32 10.1.46.4 0 1234 500 i
R4也会把该路由传给R6,
R6#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
U.U.U
Success rate is 0 percent (0/5)
虽然R6有了路由,但是R6PING不用5.5.5.5
R6#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
5.0.0.0/32 is subnetted, 1 subnets
B 5.5.5.5 [20/0] via 10.1.46.4, 00:03:22
6.0.0.0/32 is subnetted, 1 subnets
C 6.6.6.6 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.46.0 is directly connected, FastEthernet1/0
路由层面OK,但是数据层面没有
因为R6传路由到5.5.5.5, 下一跳是R4,
R4#show ip bgp
BGP table version is 2, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i5.5.5.5/32 10.1.15.5 0 100 0 500 i
R4去往5.5.5.5的下一跳路由是10.1.15.5,可是不是直连路由,需要递归查找
R4#show ip route 10.1.15.5
Routing entry for 10.1.15.0/24
Known via "ospf 1", distance 110, metric 4, type intra area
Last update from 10.1.34.3 on FastEthernet0/0, 00:22:31 ago
Routing Descriptor Blocks:
* 10.1.34.3, from 1.1.1.1, 00:22:31 ago, via FastEthernet0/0
Route metric is 4, traffic share count is 1
递归显示下一跳是10.1.34.3
R4传给R3后,
R3#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
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/3] via 10.1.23.2, 00:28:24, FastEthernet1/0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.23.2, 00:28:24, FastEthernet1/0
3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/2] via 10.1.34.4, 00:24:00, FastEthernet0/0
10.0.0.0/24 is subnetted, 5 subnets
O 10.1.15.0 [110/3] via 10.1.23.2, 00:28:24, FastEthernet1/0
O 10.1.12.0 [110/2] via 10.1.23.2, 00:28:24, FastEthernet1/0
C 10.1.23.0 is directly connected, FastEthernet1/0
O 10.1.46.0 [110/2] via 10.1.34.4, 00:24:00, FastEthernet0/0
C 10.1.34.0 is directly connected, FastEthernet0/0
通过查看发现R3中没有5.5.5.5的路由,因为R2R3没有运行BGP
解决办法就是让R2R3都运行BGP,当路由器多时,都运行BGP,都会占用资源,都需要维护IBGP邻居关系
4.3.1.3.1 解决办法1:MPLS
让数据包躲在标签后面,R1R2R3R4运行MPLS,激活邻居关系
R1配置MPLS
R1(config)#mpls ldp router-id loopback 0
R1(config)#mpls label range 100 199
R1(config)#interface fastEthernet 0/0
R1(config-if)#mpls ip
R2配置MPLS
R2(config)#mpls ldp router-id loopback 0
R2(config)#mpls label range 200 299
R2(config)#interface fastEthernet 0/0
R2(config-if)#mpls ip
R2(config)#interface fastEthernet 1/0
R2(config-if)#mpls ip
R3配置MPLS
R3(config)#mpls ldp router-id loopback 0
R3(config)#mpls label range 300 399
R3(config)#interface fastEthernet 1/0
R3(config-if)#mpls ip
R3(config)#interface fastEthernet 0/0
R3(config-if)#mpls ip
R4配置MPLS
R4(config)#mpls ldp router-id loopback 0
R4(config)#mpls label range 400 499
R4(config)#interface fastEthernet 0/0
R4(config-if)#mpls ip
R6#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
这时依旧还是PING不通,因为R5没有回程路由
R5(config)#ip route 0.0.0.0 0.0.0.0 10.1.15.1
添加一条默认路由
R6#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 136/147/160 ms
这时就可以PING通了
R3#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
1.0.0.0/32 is subnetted, 1 subnets
O 1.1.1.1 [110/3] via 10.1.23.2, 00:50:17, FastEthernet1/0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.23.2, 00:50:17, FastEthernet1/0
3.0.0.0/32 is subnetted, 1 subnets
C 3.3.3.3 is directly connected, Loopback0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/2] via 10.1.34.4, 00:45:52, FastEthernet0/0
10.0.0.0/24 is subnetted, 5 subnets
O 10.1.15.0 [110/3] via 10.1.23.2, 00:50:17, FastEthernet1/0
O 10.1.12.0 [110/2] via 10.1.23.2, 00:50:17, FastEthernet1/0
C 10.1.23.0 is directly connected, FastEthernet1/0
O 10.1.46.0 [110/2] via 10.1.34.4, 00:45:52, FastEthernet0/0
C 10.1.34.0 is directly connected, FastEthernet0/0
R2R3并没有5.5.5.5的路由,但是为什么能PING通?
R6#traceroute 5.5.5.5
R6#traceroute 5.5.5.5
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 10.1.46.4 20 msec 20 msec 24 msec
2 10.1.34.3 [MPLS: Label 304 Exp 0] 128 msec 120 msec 132 msec
3 10.1.23.2 [MPLS: Label 203 Exp 0] 120 msec 120 msec 128 msec
4 10.1.12.1 124 msec 116 msec 128 msec
5 10.1.15.5 144 msec 140 msec *
TRACER路径,没有显示标签
R6(config)#interface fastEthernet 1/0
R6(config-if)#mpls ip
R5的接口上运行LDP,这个本身不会有影响,因为R4相连的接口没有启动MPLS IP,只是为了用来显示查看标签
R6#traceroute 5.5.5.5
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 10.1.46.4 24 msec 16 msec 32 msec
2 10.1.34.3 [MPLS: Label 304 Exp 0] 92 msec 108 msec 96 msec
3 10.1.23.2 [MPLS: Label 203 Exp 0] 132 msec 112 msec 132 msec
4 10.1.12.1 116 msec 112 msec 120 msec
5 10.1.15.5 148 msec 116 msec *
TRACERT带标签
R6发一个数据包到R4,
R4#show ip cef 5.5.5.5 detail
5.5.5.5/32, epoch 0
recursive via 10.1.15.5
nexthop 10.1.34.3 FastEthernet0/0 label 304
R4收到后,查看CEF表,下一跳为R3,需要压入R3给5.5.5.5的标签304
R3#show mpls ldp bindings
lib entry: 1.1.1.1/32, rev 2
local binding: label: 300
remote binding: lsr: 2.2.2.2:0, label: 200
remote binding: lsr: 4.4.4.4:0, label: 400
lib entry: 2.2.2.2/32, rev 4
local binding: label: 301
remote binding: lsr: 2.2.2.2:0, label: imp-null
remote binding: lsr: 4.4.4.4:0, label: 401
lib entry: 3.3.3.3/32, rev 6
local binding: label: imp-null
remote binding: lsr: 2.2.2.2:0, label: 201
remote binding: lsr: 4.4.4.4:0, label: 402
lib entry: 4.4.4.4/32, rev 8
local binding: label: 302
remote binding: lsr: 2.2.2.2:0, label: 202
remote binding: lsr: 4.4.4.4:0, label: imp-null
lib entry: 10.1.12.0/24, rev 10
local binding: label: 303
remote binding: lsr: 2.2.2.2:0, label: imp-null
remote binding: lsr: 4.4.4.4:0, label: 403
lib entry: 10.1.15.0/24, rev 12
local binding: label: 304
remote binding: lsr: 2.2.2.2:0, label: 203
remote binding: lsr: 4.4.4.4:0, label: 404
lib entry: 10.1.23.0/24, rev 14
local binding: label: imp-null
remote binding: lsr: 2.2.2.2:0, label: imp-null
remote binding: lsr: 4.4.4.4:0, label: 405
lib entry: 10.1.34.0/24, rev 16
local binding: label: imp-null
remote binding: lsr: 2.2.2.2:0, label: 204
remote binding: lsr: 4.4.4.4:0, label: imp-null
lib entry: 10.1.46.0/24, rev 18
local binding: label: 305
remote binding: lsr: 2.2.2.2:0, label: 205
remote binding: lsr: 4.4.4.4:0, label: imp-null
R3中找到304标签
lib entry: 10.1.15.0/24, rev 12
local binding: label: 304
remote binding: lsr: 2.2.2.2:0, label: 203
remote binding: lsr: 4.4.4.4:0, label: 404
这个是R3给10.1.15.0/24路由前缀分的标签
R4压入R3给10.1.15.0路由前缀分的标签?注意LDP不会为BGP分配标签,只会为IGP分配
R4#show ip bgp
BGP table version is 2, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i5.5.5.5/32 10.1.15.5 0 100 0 500 i
而R4中5.5.5.5是BGP的路由,不是IGP路由
R3中没有5.5.5.5,所以也就不会有5.5.5.5的前缀标签,但是LDP又不会给BGP分配标签,这就意味着R3中不会有5.5.5.5的标签。
看到在R4路由表中,5.5.5.5的路由下一跳是10.1.15.5,虽然不能用BGP中5.5.5.5的前缀标签,但是可以用下一跳10.1.15.5在IGP路由中,所以R4用10.1.15.5标签,R3给的。
R3#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
300 200 1.1.1.1/32 0 Fa1/0 10.1.23.2
301 Pop Label 2.2.2.2/32 0 Fa1/0 10.1.23.2
302 Pop Label 4.4.4.4/32 0 Fa0/0 10.1.34.4
303 Pop Label 10.1.12.0/24 454 Fa1/0 10.1.23.2
304 203 10.1.15.0/24 590 Fa1/0 10.1.23.2
305 Pop Label 10.1.46.0/24 570 Fa0/0 10.1.34.4
R3收到后,R3给10.1.15.5将304标签替换为203,后发给R2
R2#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
200 Pop Label 1.1.1.1/32 0 Fa0/0 10.1.12.1
201 Pop Label 3.3.3.3/32 0 Fa1/0 10.1.23.3
202 302 4.4.4.4/32 0 Fa1/0 10.1.23.3
203 Pop Label 10.1.15.0/24 570 Fa0/0 10.1.12.1
204 Pop Label 10.1.34.0/24 508 Fa1/0 10.1.23.3
205 305 10.1.46.0/24 590 Fa1/0 10.1.23.3
R2收到后,R2发现203对应的为POP,将203弹出变为IP包,交给R1
R1#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
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.12.2, 00:11:14, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/3] via 10.1.12.2, 00:10:58, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/4] via 10.1.12.2, 00:09:39, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
B 5.5.5.5 [20/0] via 10.1.15.5, 00:07:09
10.0.0.0/24 is subnetted, 5 subnets
C 10.1.15.0 is directly connected, FastEthernet1/0
C 10.1.12.0 is directly connected, FastEthernet0/0
O 10.1.23.0 [110/2] via 10.1.12.2, 00:11:28, FastEthernet0/0
O 10.1.46.0 [110/4] via 10.1.12.2, 00:09:53, FastEthernet0/0
O 10.1.34.0 [110/3] via 10.1.12.2, 00:10:03, FastEthernet0/0
R1查询CEF表,发现去往5.5.5.5的是10.1.15.5,转给了R5
总结,没有运行MPLS不用的原因是因为R2R3出现了路由黑洞,没有运行BGP,也就没有5.5.5.5的路由,出现了丢包。运行MPLS后,就通了。(LDP不会为BGP发标签,但是可以为BGP递归的下一跳的标签走)
4.3.1.3.2 解决办法2:MPLS
之前试验中,在OSPF中宣告了R1R4外连的直连网段,所以R1R4有了去往R5R6的路由,就可以为去往R5R6的路由分发标签。
BGP环境中,一般情况下,不会通告AS外路由进OSPF的。即R1R4不应该通告直连路由进OSPF。
R1(config)#router ospf 1
R1(config-router)#no network 10.1.15.1 0.0.0.0 area 0
R4(config)#router ospf 1
R4(config-router)#no network 10.1.46.4 0.0.0.0 area 0
R4#show ip bgp
BGP table version is 3, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
* i5.5.5.5/32 10.1.15.5 0 100 0 500 i
不通告时, R4就没有了5.5.5.5的路由,也就不会优化>。
这时可以直接在R1R4上分别指NEXT-HOP
R1(config)#router bgp 1234
R1(config-router)#neighbor 10.1.34.4 next-hop-self
R4(config)#router bgp 1234
R4(config-router)#neighbor 10.1.12.1 next-hop-self
R4#show ip bgp
BGP table version is 4, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i5.5.5.5/32 10.1.12.1 0 100 0 500 i
这时R4上的BGP路由就优化了,下一跳直接指向R1
R6#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
这时R6是PING不通R5的。
R4#show ip cef 5.5.5.5
5.5.5.5/32
nexthop 10.1.34.3 FastEthernet0/0 label 303
R4BGP中,下一跳指向R1,CEF表中是压入标签303,正常情况下是下一跳给的标签,即10.1.12.1给的标签,发给R3
R3#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
300 200 1.1.1.1/32 0 Fa1/0 10.1.23.2
301 Pop Label 2.2.2.2/32 0 Fa1/0 10.1.23.2
302 Pop Label 4.4.4.4/32 0 Fa0/0 10.1.34.4
303 Pop Label 10.1.12.0/24 4199 Fa1/0 10.1.23.2
R3中303的标签是POP,这时变成IP包,传给了R2,
R2收到IP包后,没有5.5.5.5的路由,就丢弃了。
为什么R3要把标签弹出?因为PHP,R4压标签,用的是R1-R2的标签,R3给的,R3接着发时,需要用到R2给的标签,而R2给R1-R2分配的是IMP-NULL(因为直连),所以R2通告给R3是是弹出。问题出在R2这里。
解决办法:之前R1和R4的直连关系建立在直连接口上,应该建立在LOOPBACK接口上。
之前5.5.5。5的下一跳是10.1.12.1,现在变成R1的LP接口1.1.1.1,这时R4发数据给R5时,递归发现5.5.5.5的下一跳是1.1.1.1(5.5.5.5是BGP路由,LDP不用,用BGP的下一跳路由),而1.1.1.1是IGP路由,就可以用1.1.1.1的标签进行转发。
R1(config)#router bgp 1234
R1(config-router)#no neighbor 10.1.34.4
R1(config-router)#neighbor 4.4.4.4 remote-as 1234
R1(config-router)#neighbor 4.4.4.4 update-source loopback 0
R1(config-router)#neighbor 4.4.4.4 next-hop-self
R4(config)#router bgp 1234
R4(config-router)#no neighbor 10.1.12.1
R4(config-router)#neighbor 1.1.1.1 remote-as 1234
R4(config-router)#neighbor 1.1.1.1 update-source loopback 0
R4(config-router)#neighbor 1.1.1.1 next-hop-self
R6#ping 5.5.5.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
依旧PING不通
R6PINGR5,可以过去,回来时,R5因为默认路由,可以给R1,由于之前R1和R4删除了直连路由进OSPF,所以R1上没有去往10.1.46.6的路由。
这时需要把R6的6.6.6.6路由放进BGP,R1就有了6.6.6.6的路由。
R6(config)#router bgp 600
R6(config-router)#network 6.6.6.6 mask 255.255.255.255
R4#show ip bgp
BGP table version is 9, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*>i5.5.5.5/32 1.1.1.1 0 100 0 500 i
*> 6.6.6.6/32 10.1.46.6 0 0 600 i
R1#show ip bgp
BGP table version is 3, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 5.5.5.5/32 10.1.15.5 0 0 500 i
*>i6.6.6.6/32 4.4.4.4 0 100 0 600 i
这时R1和R4上就有了6.6.6.6的路由,而且是优化的
R6#ping 5.5.5.5 source 6.6.6.6
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 5.5.5.5, timeout is 2 seconds:
Packet sent with a source address of 6.6.6.6
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 124/146/172 ms
这时就可以PING通了
R6#traceroute 5.5.5.5 source 6.6.6.6
Type escape sequence to abort.
Tracing the route to 5.5.5.5
1 10.1.46.4 20 msec 24 msec 24 msec
2 10.1.34.3 [MPLS: Label 300 Exp 0] 140 msec 76 msec 136 msec
3 10.1.23.2 [MPLS: Label 200 Exp 0] 120 msec 124 msec 104 msec
4 10.1.12.1 136 msec 120 msec 120 msec
5 10.1.15.5 148 msec 144 msec *
TRACERT查看路径
R3#show mpls ldp bindings
lib entry: 1.1.1.1/32, rev 2
local binding: label: 300
remote binding: lsr: 2.2.2.2:0, label: 200
remote binding: lsr: 4.4.4.4:0, label: 400
R3给1.1.1.1分配的标签是300,即R4收到R6包后,BGP路由递归找到下一跳是1.1.1.1。
R3#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
300 200 1.1.1.1/32 5181 Fa1/0 10.1.23.2
301 Pop Label 2.2.2.2/32 0 Fa1/0 10.1.23.2
302 Pop Label 4.4.4.4/32 4573 Fa0/0 10.1.34.4
303 Pop Label 10.1.12.0/24 6442 Fa1/0 10.1.23.2
R3收到后,把300置换为200,发给R2
R2#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
200 Pop Label 1.1.1.1/32 5266 Fa0/0 10.1.12.1
201 Pop Label 3.3.3.3/32 0 Fa1/0 10.1.23.3
202 302 4.4.4.4/32 4875 Fa1/0 10.1.23.3
204 Pop Label 10.1.34.0/24 5318 Fa1/0 10.1.23.3
R2针对标签为200的路由是POP,发IP包给R1
R1#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
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
O 2.2.2.2 [110/2] via 10.1.12.2, 00:39:19, FastEthernet0/0
3.0.0.0/32 is subnetted, 1 subnets
O 3.3.3.3 [110/3] via 10.1.12.2, 00:39:19, FastEthernet0/0
4.0.0.0/32 is subnetted, 1 subnets
O 4.4.4.4 [110/4] via 10.1.12.2, 00:39:19, FastEthernet0/0
5.0.0.0/32 is subnetted, 1 subnets
B 5.5.5.5 [20/0] via 10.1.15.5, 00:54:29
6.0.0.0/32 is subnetted, 1 subnets
B 6.6.6.6 [200/0] via 4.4.4.4, 00:05:58
10.0.0.0/24 is subnetted, 4 subnets
C 10.1.15.0 is directly connected, FastEthernet1/0
C 10.1.12.0 is directly connected, FastEthernet0/0
O 10.1.23.0 [110/2] via 10.1.12.2, 00:39:30, FastEthernet0/0
10.1.34.0 [110/3] via 10.1.12.2, 00:39:30, FastEthernet0/0
R1发现去往5.5.5.5的下一条是10.1.15.5,也就到了R5.
R5回包给R6.
R5#show ip bgp
BGP table version is 3, local router ID is 5.5.5.5
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 5.5.5.5/32 0.0.0.0 0 32768 i
*> 6.6.6.6/32 10.1.15.1 0 1234 600 i
R5查看BGP路由,下一跳是10.1.15.1,即R1
R1#show ip cef 6.6.6.6
6.6.6.6/32
nexthop 10.1.12.2 FastEthernet0/0 label 202
R1收到包后,查CEF表,压入标签为202,下一跳给R2
R1#show mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
100 Pop Label 2.2.2.2/32 0 Fa0/0 10.1.12.2
101 201 3.3.3.3/32 0 Fa0/0 10.1.12.2
102 202 4.4.4.4/32 0 Fa0/0 10.1.12.2
103 Pop Label 10.1.23.0/24 0 Fa0/0 10.1.12.2
104 204 10.1.34.0/24 0 Fa0/0 10.1.12.2
R1给去往4.4.4.4的标签202是R2分配的,,一次下去。