EIGRP优化—路由汇总
- EIGRP路由汇总
- 自动汇总
- 手动汇总
EIGRP路由汇总
汇总路由会进一步加快EIGRP的收敛时间，假如一台路由器收到一条某个网络查询消息时，而该网络正好被自己路由表中的一条汇总路由所包括，那么它便会立即对此查询进行应答。
自动汇总
自动汇总是EIGRP默认启动的根据主类网络类型进行的自动汇总，
我们以以下网络为例：
对R1进行配置：
R1(config)#int f0/0
R1(config-if)#ip add 192.168.1.1 255.255.255.0
R1(config-if)#no sh
R1(config-if)#int f0/1
R1(config-if)#ip add 192.168.2.1 255.255.255.0
R1(config-if)#no sh
R1(config-if)#int lo 0
R1(config-if)#ip add 1.1.1.1 255.255.255.0
R1(config-if)#no sh
R1(config)#router eigrp 100
R1(config-router)#no au
R1(config-router)#network 1.1.1.0 0.0.0.255
R1(config-router)#network 192.168.0.0 0.0.255.255
对R2进行配置：
R2(config)#int f0/0
R2(config-if)#ip add 192.168.1.2 255.255.255.0
R2(config-if)#no sh
R2(config-if)#int lo 0
R2(config-if)#ip add 10.10.0.1 255.255.0.0
R2(config-if)#no sh
R2(config-if)#int lo 1
R2(config-if)#ip add 10.11.0.1 255.255.0.0
R2(config-if)#no sh
R2(config-if)#int lo 2
R2(config-if)#ip add 10.12.0.1 255.255.0.0
R2(config-if)#no sh
R2(config-if)#int lo 3
R2(config-if)#ip add 10.13.0.1 255.255.0.0
R2(config-if)#no sh
R2(config)#router eigrp 100
R2(config-router)#no au
R2(config-router)#network 10.0.0.0 0.255.255.255
R2(config-router)#network 192.168.1.0 0.0.0.255
对R3进行配置
R3(config)#int f0/1
R3(config-if)#ip add 192.168.2.2 255.255.255.0
R3(config-if)#no sh
R3(config-if)#int lo 0
R3(config-if)#ip add 10.64.0.1 255.255.0.0
R3(config-if)#no sh
R3(config-if)#int lo 1
R3(config-if)#ip add 10.65.0.1 255.255.0.0
R3(config-if)#no sh
R3(config-if)#int lo 2
R3(config-if)#ip add 10.66.0.1 255.255.0.0
R3(config-if)#no sh
R3(config)#router e 100
R3(config-router)#no au
R3(config-router)#network 10.0.0.0 0.255.255.255
R3(config-router)#network 192.168.0.0 0.0.255.255
这时我们查看以下R1的路由表
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
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
10.0.0.0/16 is subnetted, 7 subnets
D 10.10.0.0 [90/409600] via 192.168.1.2, 00:08:37, FastEthernet0/0
D 10.11.0.0 [90/409600] via 192.168.1.2, 00:08:37, FastEthernet0/0
D 10.12.0.0 [90/409600] via 192.168.1.2, 00:08:37, FastEthernet0/0
D 10.13.0.0 [90/409600] via 192.168.1.2, 00:08:37, FastEthernet0/0
D 10.66.0.0 [90/409600] via 192.168.2.2, 00:07:41, FastEthernet0/1
D 10.64.0.0 [90/409600] via 192.168.2.2, 00:07:43, FastEthernet0/1
D 10.65.0.0 [90/409600] via 192.168.2.2, 00:07:43, FastEthernet0/1
C 192.168.1.0/24 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
由标识D标志的7条路由条目为R1通过EIGRP收到的7个不同的内部网络。
我们先来尝试自动汇总
在R2上配置自动汇总
R2(config)#router eigrp 100 启用自动汇总时，邻居关系不会终止，而auto-summary这条命令会在有类网络边界自动汇总，而不需手动输入掩码。这条命令默认启动。
R2(config-router)#auto-summary
我们继续在R1上查看汇总的路由
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
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D 10.0.0.0/8 [90/409600] via 192.168.1.2, 00:00:05, FastEthernet0/0
D 10.66.0.0/16 [90/409600] via 192.168.2.2, 00:54:23, FastEthernet0/1
D 10.64.0.0/16 [90/409600] via 192.168.2.2, 00:54:23, FastEthernet0/1
D 10.65.0.0/16 [90/409600] via 192.168.2.2, 00:54:23, FastEthernet0/1
C 192.168.1.0/24 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
10.0.0.0/8替代了原来10.10.0.0/16~10.13.0.0/16的路由
我们再查看以下R2上的路由表
R2#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
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/409600] via 192.168.1.1, 00:58:51, FastEthernet0/0
10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
C 10.10.0.0/16 is directly connected, Loopback0
C 10.11.0.0/16 is directly connected, Loopback1
C 10.12.0.0/16 is directly connected, Loopback2
C 10.13.0.0/16 is directly connected, Loopback3
D 10.0.0.0/8 is a summary, 00:03:39, Null0
D 10.66.0.0/16 [90/435200] via 192.168.1.1, 00:57:56, FastEthernet0/0
D 10.64.0.0/16 [90/435200] via 192.168.1.1, 00:57:57, FastEthernet0/0
D 10.65.0.0/16 [90/435200] via 192.168.1.1, 00:57:57, FastEthernet0/0
C 192.168.1.0/24 is directly connected, FastEthernet0/0
D 192.168.2.0/24 [90/307200] via 192.168.1.1, 00:58:53, FastEthernet0/0
我门看见这里多出了一条描述为10.0.0.0/8的目的网络，出接口为Null0。当配置了自动汇总后，这条路由会自动写入路由表，为了避免环路。假如R2接收到了一条被包括在10.0.0.0/8中的数据包，但却并不在路由表中，万一R2配置有去往R1的默认路由，则会把这个数据包发送给R1，而R1收到这个数据包后会根据汇总路由将其发回给R2，这样就会无限制的循环下去知道到达生存时间。所以这里将这条汇总路由写入路由表，并且出接口是Null0，这样就有效的防止了路由环路。
接下来我们再在R3上配置自动汇总
R3(config)#router eigrp 100 之后我们继续在R1上查看路由表
R3(config-router)#auto-summary
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
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
D 10.0.0.0/8 [90/409600] via 192.168.2.2, 00:00:35, FastEthernet0/1
[90/409600] via 192.168.1.2, 00:00:35, FastEthernet0/0
C 192.168.1.0/24 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
我们可以看到，R2与R3上面的网络汇总之后都是10.0.0.0/8，所以R1收到了完全相同的汇总路由！而这两条路有有相同的开销（409600），所以会在这两条路有间执行等价负载均衡（后面介绍）。
我们尝试从R1ping10.10.0.1与10.11.0.1：
R1#ping 10.10.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.0.1, timeout is 2 seconds:
UUUUU
Success rate is 0 percent (0/5)
R1#ping 10.11.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.11.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/34/60 ms
在相同主机上的两个目的网络一个可达一个不可达（这次连通性测试发生什么情况都是有可能的，因为此路由已经不可靠，你不确定自己ping会不会通）说明由于汇总路由将两个邻居的网络都包含在内，这样R1很有可能将数据包发送给错误的邻居。
所以，自动汇总在无类网络不连续的网络中会造成连通性问题。因此只能在极少数情况下才有用，非常不建议使用自动汇总。
手动汇总
EIGRP手动汇总是需要我们人工进行计算来汇总路由，假如在这个例子中如何来手工汇总呢：
使用我们刚刚学习子网掩码时的知识，很容易将这四个网段汇总为掩码为/13的一条路由：10.8.0.0/13。可见，R2上的所有换回口都被此汇总路由所包括，而R3上的10.64.0.0缺不被这个路由包括。
下面我们在R2上配置手动汇总：
R2(config)#router eigrp 100
R2(config-router)#no auto-summary
R2(config)#int f0/0
R2(config-if)#ip summary-address eigrp 100 10.8.0.0 255.248.0.0
在EIGRP协议配置中使用no auto-summary 是关闭自动汇总，然后在需要发送汇总路由的端口进行手工汇总，命令为：ip summary-address eigrp as号 汇总ip 汇总掩码。
我们先关闭R3的自动汇总后再去R1看一下路由表：
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
1.0.0.0/24 is subnetted, 1 subnets
C 1.1.1.0 is directly connected, Loopback0
10.0.0.0/8 is variably subnetted, 4 subnets, 2 masks
D 10.8.0.0/13 [90/409600] via 192.168.1.2, 00:09:09, FastEthernet0/0
D 10.66.0.0/16 [90/409600] via 192.168.2.2, 00:00:03, FastEthernet0/1
D 10.64.0.0/16 [90/409600] via 192.168.2.2, 00:00:03, FastEthernet0/1
D 10.65.0.0/16 [90/409600] via 192.168.2.2, 00:00:03, FastEthernet0/1
C 192.168.1.0/24 is directly connected, FastEthernet0/0
C 192.168.2.0/24 is directly connected, FastEthernet0/1
这条便是汇总路由
我们回到R2看一眼路由表;
R2#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
1.0.0.0/24 is subnetted, 1 subnets
D 1.1.1.0 [90/409600] via 192.168.1.1, 02:14:40, FastEthernet0/0
10.0.0.0/8 is variably subnetted, 8 subnets, 2 masks
C 10.10.0.0/16 is directly connected, Loopback0
C 10.11.0.0/16 is directly connected, Loopback1
D 10.8.0.0/13 is a summary, 00:09:58, Null0
C 10.12.0.0/16 is directly connected, Loopback2
C 10.13.0.0/16 is directly connected, Loopback3
D 10.66.0.0/16 [90/435200] via 192.168.1.1, 00:00:52, FastEthernet0/0
D 10.64.0.0/16 [90/435200] via 192.168.1.1, 00:00:53, FastEthernet0/0
D 10.65.0.0/16 [90/435200] via 192.168.1.1, 00:00:53, FastEthernet0/0
C 192.168.1.0/24 is directly connected, FastEthernet0/0
D 192.168.2.0/24 [90/307200] via 192.168.1.1, 02:14:42, FastEthernet0/0
与自动汇总一样，为了防止出现环路，将次汇总以端口Null0为出接口写入到本机路由表中。
我们再来测试网络的连通性：
R1#ping 10.10.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.10.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/31/68 ms
R1#ping 10.11.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.11.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/31/48 ms
R1#ping 10.64.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.64.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 16/29/44 ms
R1#ping 10.65.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.65.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 12/39/52 ms
由此可见，网络已经连通！