【技术分享】EIGRP不等价负载均衡
实验目的
了解EIGRP等价负载均衡；
了解EIGRP不等价负载均衡；
掌握EIGRP不等价负载均衡实现的方法。
实验拓扑
实验需求
根据实验拓扑图，完成设备的基本配置；
在R1、R2、R3上启用EIGRP 100，关闭自动汇总并宣告相应的接口；
通过配置R2，使得R2去往R3的环回口实现不等价负载均衡。
实验步骤
设备基本配置
R1的基本配置如下：
hostname R1
interface serial0/1/0
clock rate 64000
ip address 12.1.1.1 255.255.255.0
no shutdown
interface serial0/1/1
clock rate 64000
ip address 13.1.1.1 255.255.255.0
no shutdown
interface loopback1
ip address 10.1.1.1 255.255.255.0
interface loopback2
ip address 10.1.2.1 255.255.255.0
interface loopback3
ip address 10.1.3.1 255.255.255.0
R2的基本配置如下：
hostname R2
interface serial0/0
ip address 12.1.1.2 255.255.255.0
no shutdown
interface serial0/1
clock rate 64000
ip address 23.1.1.2 255.255.255.0
no shut
interface loopback1
ip address 20.1.1.1 255.255.255.0
interface loopback2
ip address 20.1.2.1 255.255.255.0
interface loopback3
ip address 20.1.3.1 255.255.255.0
R3的基本配置如下：
hostname R3
interface serial0/0
ip address 13.1.1.3 255.255.255.0
no shutdown
interface serial0/1
ip address 23.1.1.3 255.255.255.0
no shut
interface loopback1
ip address 30.1.1.1 255.255.255.0
interface loopback2
ip address 30.1.2.1 255.255.255.0
interface loopback3
ip address 30.1.3.1 255.255.255.0在R1、R2、R3上配置EIGRP 100
R1的EIGRP配置如下：
router eigrp 100
no auto-summary
network 12.1.1.0 0.0.0.255
network 13.1.1.0 0.0.0.255
network 10.1.1.0 0.0.0.255
network 10.1.2.0 0.0.0.255
network 10.1.3.0 0.0.0.255
R2的EIGRP配置如下：
router eigrp 100
no auto-summary
network 12.1.1.0 0.0.0.255
network 23.1.1.0 0.0.0.255
network 20.1.1.0 0.0.0.255
network 20.1.2.0 0.0.0.255
network 20.1.3.0 0.0.0.255
R3的EIGRP配置如下：
router eigrp 100
no auto-summary
network 13.1.1.0 0.0.0.255
network 23.1.1.0 0.0.0.255
network 30.1.1.0 0.0.0.255
network 30.1.2.0 0.0.0.255
network 30.1.3.0 0.0.0.255在R1、R2、R3上检查EIGRP路由
R1的EIGRP路由如下：
R1#show ip route eigrp
20.0.0.0/24 is subnetted, 3 subnets
D 20.1.1.0 [90/2297856] via 12.1.1.2, 00:01:16, Serial0/1/0
D 20.1.3.0 [90/2297856] via 12.1.1.2, 00:01:16, Serial0/1/0
D 20.1.2.0 [90/2297856] via 12.1.1.2, 00:01:16, Serial0/1/0
23.0.0.0/24 is subnetted, 1 subnets
D 23.1.1.0 [90/2681856] via 13.1.1.3, 00:01:16, Serial0/1/1
[90/2681856] via 12.1.1.2, 00:01:16, Serial0/1/0
30.0.0.0/24 is subnetted, 3 subnets
D 30.1.3.0 [90/2297856] via 13.1.1.3, 00:01:16, Serial0/1/1
D 30.1.2.0 [90/2297856] via 13.1.1.3, 00:01:16, Serial0/1/1
D 30.1.1.0 [90/2297856] via 13.1.1.3, 00:01:16, Serial0/1/1R1去往23.1.1.0/24存在两条路径，一条通过R2到达另外一条通过R3到达，但是不管通过R2到达还是通过R3到达，沿途路径的Metric是相等的，又因为都是通过EIGRP学习到的路由，AD值都是90，所以R1路由表里面去往23.1.1.0/24是等价负载的路径。
R2的EIGRP路由如下：
R2#show ip route eigrp
10.0.0.0/24 is subnetted, 3 subnets
D 10.1.3.0 [90/2297856] via 12.1.1.1, 00:01:56, Serial0/0
D 10.1.2.0 [90/2297856] via 12.1.1.1, 00:01:56, Serial0/0
D 10.1.1.0 [90/2297856] via 12.1.1.1, 00:01:56, Serial0/0
13.0.0.0/24 is subnetted, 1 subnets
D 13.1.1.0 [90/2681856] via 23.1.1.3, 00:01:56, Serial0/1
[90/2681856] via 12.1.1.1, 00:01:56, Serial0/0
30.0.0.0/24 is subnetted, 3 subnets
D 30.1.3.0 [90/2297856] via 23.1.1.3, 00:01:56, Serial0/1
D 30.1.2.0 [90/2297856] via 23.1.1.3, 00:01:56, Serial0/1
D 30.1.1.0 [90/2297856] via 23.1.1.3, 00:01:56, Serial0/1R3的EIGRP路由如下：
R3#show ip route eigrp
20.0.0.0/24 is subnetted, 3 subnets
D 20.1.1.0 [90/2297856] via 23.1.1.2, 00:00:02, Serial0/1
D 20.1.3.0 [90/2297856] via 23.1.1.2, 00:00:02, Serial0/1
D 20.1.2.0 [90/2297856] via 23.1.1.2, 00:00:02, Serial0/1
10.0.0.0/24 is subnetted, 3 subnets
D 10.1.3.0 [90/2297856] via 13.1.1.1, 00:00:02, Serial0/0
D 10.1.2.0 [90/2297856] via 13.1.1.1, 00:00:02, Serial0/0
D 10.1.1.0 [90/2297856] via 13.1.1.1, 00:00:02, Serial0/0
12.0.0.0/24 is subnetted, 1 subnets
D 12.1.1.0 [90/2681856] via 23.1.1.2, 00:00:02, Serial0/1
[90/2681856] via 13.1.1.1, 00:00:02, Serial0/0EIGRP不等价负载均衡的实现
首先我们来看R2的EIGRP拓扑表：
R2#show ip eigrp topology
IP-EIGRP Topology Table for AS(100)/ID(20.1.3.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.1.3.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 10.1.2.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 10.1.1.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 12.1.1.0/24, 1 successors, FD is 2169856
via Connected, Serial0/0
P 13.1.1.0/24, 2 successors, FD is 2681856
via 12.1.1.1 (2681856/2169856), Serial0/0
via 23.1.1.3 (2681856/2169856), Serial0/1
P 20.1.1.0/24, 1 successors, FD is 128256
via Connected, Loopback1
P 20.1.3.0/24, 1 successors, FD is 128256
via Connected, Loopback3
P 20.1.2.0/24, 1 successors, FD is 128256
via Connected, Loopback2
P 23.1.1.0/24, 1 successors, FD is 2169856
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
via Connected, Serial0/1
P 30.1.3.0/24, 1 successors, FD is 2297856
via 23.1.1.3 (2297856/128256), Serial0/1
P 30.1.2.0/24, 1 successors, FD is 2297856
via 23.1.1.3 (2297856/128256), Serial0/1
P 30.1.1.0/24, 1 successors, FD is 2297856
via 23.1.1.3 (2297856/128256), Serial0/1发现R2去往R3的三个环回口下一跳都为23.1.1.3，存在Successor R3，FD为2297856，AD为128256。事实上R2去往这三个网段是存在两条路径的，一条路径通过R1到达，另外一条路径通过R3到达，但是为什么R1没有成为Feasible Successor呢？我们来看R2详细的拓扑表：
R2#show ip eigrp topology all-links
IP-EIGRP Topology Table for AS(100)/ID(20.1.3.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.1.3.0/24, 1 successors, FD is 2297856, serno 148
via 12.1.1.1 (2297856/128256), Serial0/0
via 23.1.1.3 (2809856/2297856), Serial0/1
P 10.1.2.0/24, 1 successors, FD is 2297856, serno 147
via 12.1.1.1 (2297856/128256), Serial0/0
via 23.1.1.3 (2809856/2297856), Serial0/1
P 10.1.1.0/24, 1 successors, FD is 2297856, serno 146
via 12.1.1.1 (2297856/128256), Serial0/0
via 23.1.1.3 (2809856/2297856), Serial0/1
P 12.1.1.0/24, 1 successors, FD is 2169856, serno 35
via Connected, Serial0/0
P 13.1.1.0/24, 2 successors, FD is 2681856, serno 149
via 12.1.1.1 (2681856/2169856), Serial0/0
via 23.1.1.3 (2681856/2169856), Serial0/1
P 20.1.1.0/24, 1 successors, FD is 128256, serno 7
via Connected, Loopback1
P 20.1.3.0/24, 1 successors, FD is 128256, serno 9
via Connected, Loopback3
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 20.1.2.0/24, 1 successors, FD is 128256, serno 8
via Connected, Loopback2
P 23.1.1.0/24, 1 successors, FD is 2169856, serno 131
via Connected, Serial0/1
P 30.1.3.0/24, 1 successors, FD is 2297856, serno 142
via 23.1.1.3 (2297856/128256), Serial0/1
via 12.1.1.1 (2809856/2297856), Serial0/0
P 30.1.2.0/24, 1 successors, FD is 2297856, serno 141
via 23.1.1.3 (2297856/128256), Serial0/1
via 12.1.1.1 (2809856/2297856), Serial0/0
P 30.1.1.0/24, 1 successors, FD is 2297856, serno 140
via 23.1.1.3 (2297856/128256), Serial0/1
via 12.1.1.1 (2809856/2297856), Serial0/0我们发现，如果R2通过R1去往R3的三个环回口，AD为2297856，FD为2809856，然而要成为Feasible Successor必须满足可行条件（FC）：AD of Second Best Route < FD of Best Route（后备路径的AD < 当前的FD），现在通过R1前往的AD为2297856，和当前的FD=2297856相等，没有满足FC，所以R1不能成为Feasible Successor。
R2上作如下修改：
interface Serial0/1
bandwidth 128
clear ip eigrp neighbor检查R2的EIGRP拓扑表：
R2#show ip eigrp topology
IP-EIGRP Topology Table for AS(100)/ID(20.1.3.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 10.1.3.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 10.1.2.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 10.1.1.0/24, 1 successors, FD is 2297856
via 12.1.1.1 (2297856/128256), Serial0/0
P 12.1.1.0/24, 1 successors, FD is 2169856
via Connected, Serial0/0
P 13.1.1.0/24, 1 successors, FD is 2681856
via 12.1.1.1 (2681856/2169856), Serial0/0
via 23.1.1.3 (21024000/2169856), Serial0/1
P 20.1.1.0/24, 1 successors, FD is 128256
via Connected, Loopback1
P 20.1.3.0/24, 1 successors, FD is 128256
via Connected, Loopback3
P 20.1.2.0/24, 1 successors, FD is 128256
via Connected, Loopback2
P 23.1.1.0/24, 1 successors, FD is 20512000
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
via Connected, Serial0/1
via 12.1.1.1 (3193856/2681856), Serial0/0
P 30.1.3.0/24, 1 successors, FD is 2809856
via 12.1.1.1 (2809856/2297856), Serial0/0
via 23.1.1.3 (20640000/128256), Serial0/1
P 30.1.2.0/24, 1 successors, FD is 2809856
via 12.1.1.1 (2809856/2297856), Serial0/0
via 23.1.1.3 (20640000/128256), Serial0/1
P 30.1.1.0/24, 1 successors, FD is 2809856
via 12.1.1.1 (2809856/2297856), Serial0/0
via 23.1.1.3 (20640000/128256), Serial0/1通过调整R2 Serial0/1接口的bandwidth之后，我们发现现在R2去往R3的三个环回口网段，Successor为R1，Feasible Successor为R3，因为通过R3前往满足可行条件（FC）：128256 < 2809869。那是不是存在Feasible Successor的情况下EIGRP就能自动实现不等价负载均衡了呢？不会！我们来观察R2的路由表：
R2#show ip route eigrp
10.0.0.0/24 is subnetted, 3 subnets
D 10.1.3.0 [90/2297856] via 12.1.1.1, 00:00:13, Serial0/0
D 10.1.2.0 [90/2297856] via 12.1.1.1, 00:00:13, Serial0/0
D 10.1.1.0 [90/2297856] via 12.1.1.1, 00:00:13, Serial0/0
13.0.0.0/24 is subnetted, 1 subnets
D 13.1.1.0 [90/2681856] via 12.1.1.1, 00:00:13, Serial0/0
30.0.0.0/24 is subnetted, 3 subnets
D 30.1.3.0 [90/2809856] via 12.1.1.1, 00:00:13, Serial0/0
D 30.1.2.0 [90/2809856] via 12.1.1.1, 00:00:13, Serial0/0
D 30.1.1.0 [90/2809856] via 12.1.1.1, 00:00:13, Serial0/0发现R2并没有负载。那存在Feasible Successor的情况下，EIGRP如何实现不等价负载均衡呢？我们要借助于variance参数，并且必须满足如下条件：
FS's FD < U*Successor's FD
当前Successor的FD为2809856，Feasible Successor的FD为20640000，要满足 以上公式U至少取8才行。对R2进行如下配置：
router eigrp 100
variance 8检查R2的路由表：
R2#show ip route eigrp
10.0.0.0/24 is subnetted, 3 subnets
D 10.1.3.0 [90/2297856] via 12.1.1.1, 00:00:04, Serial0/0
D 10.1.2.0 [90/2297856] via 12.1.1.1, 00:00:04, Serial0/0
D 10.1.1.0 [90/2297856] via 12.1.1.1, 00:00:04, Serial0/0
13.0.0.0/24 is subnetted, 1 subnets
D 13.1.1.0 [90/21024000] via 23.1.1.3, 00:00:04, Serial0/1
[90/2681856] via 12.1.1.1, 00:00:04, Serial0/0
30.0.0.0/24 is subnetted, 3 subnets
D 30.1.3.0 [90/20640000] via 23.1.1.3, 00:00:04, Serial0/1
[90/2809856] via 12.1.1.1, 00:00:04, Serial0/0
D 30.1.2.0 [90/20640000] via 23.1.1.3, 00:00:04, Serial0/1
[90/2809856] via 12.1.1.1, 00:00:04, Serial0/0
D 30.1.1.0 [90/20640000] via 23.1.1.3, 00:00:04, Serial0/1
[90/2809856] via 12.1.1.1, 00:00:04, Serial0/0发现，R2去往R3的环回口是负载均衡的，虽然AD一样，但是Metric值不一样，不等价负载均衡。
