EIGRP 管理距离 引起路由震荡的原因
EIGRP和OSPF做双点双向重分发
第一种情况：
1，R1,R2,R3,R4初始配置
R1
conf t
int l 0
ip add 1.1.1.1 255.255.255.255
int f0/0
ip add 1.1.123.1 255.255.255.0
no shut
router eigrp 1
no auto
net 1.1.1.1 0.0.0.0
net 1.1.123.0 0.0.0.255
end
R2
conf t
int l 0
ip add 1.1.2.2 255.255.255.255
int f0/0
ip add 1.1.123.2 255.255.255.0
no shut
int s1/0
ip add 1.1.234.2 255.255.255.0
encap f
no arp f
no frame inv
frame map ip 1.1.234.4 204 b
frame map ip 1.1.234.3 204 b
no shut
ip ospf p 0
router ospf 1
router-id 1.1.2.2
net 1.1.234.2 0.0.0.0 a 0
net 1.1.2.2 0.0.0.0 a 0
router eigrp 1
no auto
net 1.1.2.2 0.0.0.0
net 1.1.123.0 0.0.0.255
end
R3
conf t
int l 0
ip add 1.1.3.3 255.255.255.255
int f 0/0
ip add 1.1.123.3 255.255.255.0
no shut
int s1/0
ip add 1.1.234.3 255.255.255.0
encap f
no arp f
no frame inv
frame map ip 1.1.234.4 304 b
frame map ip 1.1.234.2 304 b
no shut
ip ospf p 0
router ospf 1
router-id 1.1.3.3
net 1.1.234.3 0.0.0.0 a 0
net 1.1.3.3 0.0.0.0 a 0
router eigrp 1
no auto
net 1.1.3.3 0.0.0.0
net 1.1.123.0 0.0.0.255
end
R4
conf t
int l 0
ip add 1.1.4.4 255.255.255.255
int s1/0
ip add 1.1.234.4 255.255.255.0
encap f
no arp f
no frame inv
frame map ip 1.1.234.2 402 b
frame map ip 1.1.234.3 403 b
no shut
router ospf 1
router-id 1.1.4.4
nei 1.1.234.2
nei 1.1.234.3
net 1.1.234.4 0.0.0.0 a 0
net 1.1.4.4 0.0.0.0 a 0
end
到这里，所有的EIGRP和OSPF邻居关系都建立好了。
2，在R2和R3上做双点双向重分发
R2
router eigrp 1
redistribute ospf 1 metric 10000 100 255 1 1500
router ospf 1
redistribute eigrp 1 metric 100 metric-type 1 subnets
end
R3
router eigrp 1
redistribute ospf 1 metric 10000 100 255 1 1500
router ospf 1
redistribute eigrp 1 metric 100 metric-type 1 subnets
end
重分发完成，
验证
R1路由表
R1#sh ip route
Gateway of last resort is not set
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
D EX 1.1.4.4/32 [170/284160] via 1.1.123.3, 00:01:03, FastEthernet0/0
[170/284160] via 1.1.123.2, 00:01:03, FastEthernet0/0
D 1.1.3.3/32 [90/156160] via 1.1.123.3, 00:08:44, FastEthernet0/0
D 1.1.2.2/32 [90/156160] via 1.1.123.2, 00:08:44, FastEthernet0/0
C 1.1.1.1/32 is directly connected, Loopback0
C 1.1.123.0/24 is directly connected, FastEthernet0/0
D EX 1.1.234.0/24 [170/284160] via 1.1.123.3, 00:02:51, FastEthernet0/0
[170/284160] via 1.1.123.2, 00:02:51, FastEthernet0/0
R4路由表
R4#sh ip route
Gateway of last resort is not set
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C 1.1.4.4/32 is directly connected, Loopback0
O 1.1.3.3/32 [110/65] via 1.1.234.3, 00:00:14, Serial1/0
O 1.1.2.2/32 [110/65] via 1.1.234.2, 00:00:14, Serial1/0
O E1 1.1.1.1/32 [110/164] via 1.1.234.3, 00:00:14, Serial1/0
[110/164] via 1.1.234.2, 00:00:14, Serial1/0
O E1 1.1.123.0/24 [110/164] via 1.1.234.3, 00:00:14, Serial1/0
[110/164] via 1.1.234.2, 00:00:14, Serial1/0
C 1.1.234.0/24 is directly connected, Serial1/0
第二种情况
在R1的S1/2接口接入R5，并启用RIPV2
R5
conf t
int s1/2
ip add 192.168.45.5 255.255.255.0
no shut
router rip
ver 2
no auto
net 192.168.45.0
end
R1
conf t
int s1/2
no shut
ip add 192.168.45.4 255.255.255.0
router rip
ver 2
no au
net 192.168.45.0
end
把RIP再分发到EIGRP1中
router eigrp 1
redistribute rip metric 10000 100 255 1 1500
end
这时看R2和R3上的路由表
R2(config)#do sh 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
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O 1.1.4.4/32 [110/65] via 1.1.234.4, 00:31:58, Serial1/0
D 1.1.3.3/32 [90/156160] via 1.1.123.3, 00:05:56, FastEthernet0/0
C 1.1.2.2/32 is directly connected, Loopback0
D 1.1.1.1/32 [90/156160] via 1.1.123.1, 00:05:56, FastEthernet0/0
C 1.1.123.0/24 is directly connected, FastEthernet0/0
C 1.1.234.0/24 is directly connected, Serial1/0
O E1 192.168.45.0/24 [110/164] via 1.1.234.3, 00:05:59, Serial1/0
R2(config)#do ping 192.168.45.5
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.45.5, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
仔细查看路由表可以发现，R2到192.168.45.0网段下一跳是1.1.234.2，也就是R3的S1/0接口，但是拓扑上表明下一跳为R1的F0 /0接口为最佳路径。为什么会出现这样的情况呢？
我们知道，EIGRP的AD(管理距离）有两种情况：
1，当收到内部路由时，AD为90，路由表里的标识为“D”
2，当收到外部转发的路由是，AD为170，路由表里的标识为“ D EX”
当R1把RIP再分发到EIGRP1中的时候，R2和R3的收到192.168.45.0网段为“D EX"标识（可以通过shou ip bgptop命令校验)，这时EIGRP的AD为170，当R2把EIGRP1再分发到OSPF中后，因为的OSPF的AD为110，R3会从R1和R2 这个两个路由器上收到192.168.45.0这个路由条目，根据路由选路原则，R3会优先选择OSPF协议收到的路由，所以在路由表上显示“OE1”， 这样的结果会造成数据包在R4和R2之间震荡，
用trace命令验证
R2(config)#do trace 192.168.45.5
Type escape sequence to abort.
Tracing the route to 192.168.45.5
1 1.1.234.4 252 msec 232 msec 232 msec
2 1.1.234.3 432 msec 308 msec 304 msec
3 * * *
4 1.1.234.4 576 msec 612 msec 480 msec
5 1.1.234.3 720 msec 464 msec 648 msec
6 * * *
7 1.1.234.4 528 msec 684 msec 552 msec
8 1.1.234.3 888 msec 932 msec 672 msec
9 * * *
……
R3上也会出现相同的情况
解决方法
将R2和R3上OSPF的AD修改为大于170
R2
conf t
access 10 permit 192.168.45.0 0.0.0.255
router ospf 1
distance 180 1.1.3.3 0.0.0.0 10
end
R3
conf t
access 10 permit 192.168.45.0 0.0.0.255
router ospf 1
distance 180 1.1.2.2 0.0.0.0 10
end
验证R2，R3，R4路由表
R2(config)#do sh 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
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O 1.1.4.4/32 [110/65] via 1.1.234.4, 00:11:38, Serial1/0
D 1.1.3.3/32 [90/156160] via 1.1.123.3, 00:11:38, FastEthernet0/0
C 1.1.2.2/32 is directly connected, Loopback0
D 1.1.1.1/32 [90/156160] via 1.1.123.1, 00:11:38, FastEthernet0/0
C 1.1.123.0/24 is directly connected, FastEthernet0/0
C 1.1.234.0/24 is directly connected, Serial1/0
D EX 192.168.45.0/24 [170/284160] via 1.1.123.1, 00:11:38, FastEthernet0/0
R3(config)#do sh 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
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
O 1.1.4.4/32 [110/65] via 1.1.234.4, 00:01:27, Serial1/0
C 1.1.3.3/32 is directly connected, Loopback0
D 1.1.2.2/32 [90/156160] via 1.1.123.2, 00:01:27, FastEthernet0/0
D 1.1.1.1/32 [90/156160] via 1.1.123.1, 00:01:27, FastEthernet0/0
C 1.1.123.0/24 is directly connected, FastEthernet0/0
C 1.1.234.0/24 is directly connected, Serial1/0
D EX 192.168.45.0/24 [170/284160] via 1.1.123.1, 00:01:27, FastEthernet0/0
R4#sh 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
1.0.0.0/8 is variably subnetted, 6 subnets, 2 masks
C 1.1.4.4/32 is directly connected, Loopback0
O 1.1.3.3/32 [110/65] via 1.1.234.3, 00:19:57, Serial1/0
O 1.1.2.2/32 [110/65] via 1.1.234.2, 00:19:57, Serial1/0
O E1 1.1.1.1/32 [110/164] via 1.1.234.3, 00:19:57, Serial1/0
[110/164] via 1.1.234.2, 00:19:57, Serial1/0
O E1 1.1.123.0/24 [110/164] via 1.1.234.3, 00:19:57, Serial1/0
[110/164] via 1.1.234.2, 00:19:57, Serial1/0
C 1.1.234.0/24 is directly connected, Serial1/0
O E1 192.168.45.0/24 [110/164] via 1.1.234.3, 00:12:25, Serial1/0
[110/164] via 1.1.234.2, 00:12:25, Serial1/0