双向双点重分发
作者：骄 子
QQ：40309630
R1#sh run
Building configuration...
Current configuration : 1823 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
ip cef
!
!
no ip dhcp use vrf connected
ip dhcp excluded-address 192.168.1.254
ip dhcp excluded-address 192.168.2.1
!
ip dhcp pool VLAN10
network 192.168.1.0 255.255.255.0
dns-server 218.1.1.1
default-router 192.168.1.254
!
ip dhcp pool VLAN20
network 192.168.2.0 255.255.255.0
dns-server 218.1.1.1
default-router 192.168.2.1
!
!
no ip domain lookup
!
multilink bundle-name authenticated
!
interface Loopback0
ip address 1.1.1 .1 255.255.255.0
!
interface FastEthernet0/0.1
encapsulation dot1Q 10
ip address 192.168.1.254 255.255.255.0
!
interface FastEthernet0/0.2
encapsulation dot1Q 20
ip address 192.168.2.1 255.255.255.0
!
interface Serial1/0
ip address 192.1.12.1 255.255.255.0
serial restart-delay 0
clock rate 64000
!
interface Serial1/1
ip address 192.1.13.1 255.255.255.0
serial restart-delay 0
clock rate 64000
!
!
router ospf 100
router-id 1.1.1 .1
log-adjacency-changes
redistribute connected subnets
network 192.1.12.0 0.0.0 .255 area 0
network 192.1.13.0 0.0.0 .255 area 0
!
no ip http server
no ip http secure-server
!
End
R2#sh run
Building configuration...
Current configuration : 1862 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
!
hostname R2
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
interface Loopback0
ip address 2.2.2 .2 255.255.255.0
!
interface FastEthernet0/0
ip address 193.1.1.1 255.255.255.0
duplex full
vrrp 10 ip 193.1.1.253
vrrp 10 priority 120
vrrp 10 authentication md5 key-string cisco
vrrp 20 ip 193.1.1.254
vrrp 20 authentication md5 key-string cisco2
!
interface Serial1/0
ip address 192.1.12.2 255.255.255.0
ip policy route-map red
serial restart-delay 0
!
!
router eigrp 90
redistribute ospf 100 metric 1000 100 255 1 1500
network 193.1.1.0
no auto-summary
!
router ospf 100
router-id 2.2.2 .2
log-adjacency-changes
redistribute eigrp 90 subnets route-map red
network 192.1.12.0 0.0.0 .255 area 0
distance 180 3.3.3 .3 0.0.0.0
!
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
access-list 10 permit 10.1.1 .0
access-list 20 permit 10.1.2 .0
access-list 30 permit 10.1.3 .0
!
!
route-map red permit 10
match ip address 10
set metric 1500
set metric-type type-1
!
route-map red deny 20
match ip address 20
!
route-map red permit 30
set metric 5000
set metric-type type-2
!
end
R3#sh run
Building configuration...
Current configuration : 1862 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R3
!
no ip domain lookup
!
multilink bundle-name authenticated
!
!
interface Loopback0
ip address 3.3.3 .3 255.255.255.0
!
interface FastEthernet0/0
ip address 193.1.1.2 255.255.255.0
duplex full
vrrp 10 ip 193.1.1.253
vrrp 10 authentication md5 key-string cisco
vrrp 20 ip 193.1.1.254
vrrp 20 priority 120
vrrp 20 authentication md5 key-string cisco2
!
interface Serial1/1
ip address 192.1.13.2 255.255.255.0
serial restart-delay 0
!!
router eigrp 90
redistribute ospf 100 metric 1000 100 255 1 1500
network 193.1.1.0
no auto-summary
!
router ospf 100
router-id 3.3.3 .3
log-adjacency-changes
redistribute eigrp 90 subnets route-map red
network 192.1.13.0 0.0.0 .255 area 0
distance 180 2.2.2 .2 0.0.0.0
!
no ip http server
no ip http secure-server
!
!
!
logging alarm informational
access-list 10 permit 10.1.1 .0
access-list 20 permit 10.1.2 .0
access-list 30 permit 10.1.3 .0
!
!
route-map red permit 10
match ip address 10
set metric 1500
set metric-type type-1
!
route-map red deny 20
match ip address 20
!
route-map red permit 30
set metric 5000
set metric-type type-2
!
End
R5>en
R5#
R5#
R5#sh run
Building configuration...
Current configuration : 1324 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R5
!
multilink bundle-name authenticated
!
!
!
!
interface Loopback0
ip address 5.5.5 .5 255.255.255.0
!
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
!
interface FastEthernet0/0
ip address 193.1.1.5 255.255.255.0
duplex full
!
!
router eigrp 90
redistribute connected
network 193.1.1.0
no auto-summary
!
no ip http server
no ip http secure-server
end
实验总结：
双向路由重分发提供了 冗余、备份还可进行负载。实验时需要在R1和R5 上面redistribute connected subnet，因为network中没有匹配到接口上面。这个实验存在着管理距离的问题！
1、 相同协议之间，度量值越小越优先；
2、 不同协议之间，管理距离越小越优先。
起初未采用distance，当我们采用show ip route 的时候，我们会发现R2或者R3上面哪个先配置redistribute哪个就是R1或者R5到1.1.1 .1或者5.5.5.5下一跳经过的路由器，而并没有负载均衡。
这里以R2先配置redistribute为例：
因为EIGRP的外部汇总路由管理距离为170，当外部汇总路由 redistribute进R1时，在R1路由表中就将添加O E2的路由条目；OSPF再通过LSA讲该条目通告给R3，此时R3也接收到外部汇总路由，通告比较，R3会选择不同协议之间 管理距离小的加入到路由表当中。这样，在查看R1的路由表时，将看到5.5.5 .5目的网络的下一跳是R2的S1/0，并不会负载均衡。
因此，我们需要解决这个问题有两种方法：
1、 减小外部汇总路由的管理距离；
2、 增多OSPF协议的管理距离。
这时需要在R1和R4上用到distance命令。然而，对于双向重分发而言。我们会发现这两种方法都行不通！原因同上！
因此，我们需要另谋良策！及在R2和R3上面控制外部汇总路由distance。同样以R2先配置为例：
当R2 redistribute外部汇总路由进来的时候，产生O E2路由，管理距离为110，同理，当R1收到这个路由条目的时候，他将发送LSA给R3。这时我们在R3上面运用distance 180 3.3.3 .3 0.0.0 .0（OSPF下面）的命令，将来自R2的外部路由管理距离更改为180（及修改O E2管理距离为180）。这时外部汇总路由也redistribute外部汇总路由（管理距离170）进来。通过比较发现，外部汇总路由优先，将被放进路由表。这样在R1上面show ip route 的时候，我们就会发现到达目的主机5.5.5.5有两个下一跳，及负载均衡了。
同理，R4端，当R2 redistribute路由信息进来时，将被加入到路由表，R4将发送更新包（LSU）到R3，R3接收到外部汇总路由和D EX路由信息，将比较他们的管理距离。Redistribute 路由信息管理距离为110，而外部汇总路由为170，将管理距离小的路由条目加入到路由表。同样负载均衡。同时，你还可以试试在EIGRP下面修改distance小于110，可以先分析一下。看可不可行？
此外，还可以通过做单向重发布和打tag的方式来解决此类问题！
大家不妨一试。
R1#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
C 192.1.12.0/24 is directly connected, Serial1/0
C 1.1.1 .0 is directly connected, Loopback0
C 192.1.13.0/24 is directly connected, Serial1/1
O E2 5.5.5 .0 [110/5000] via 192.1.13.2, 00:00:09, Serial1/1
[110/5000] via 192.1.12.2, 00:00:09, Serial1/0
O E2 10.1.3 .0 [110/5000] via 192.1.13.2, 00:00:09, Serial1/1
[110/5000] via 192.1.12.2, 00:00:09, Serial1/0
O E1 10.1.1 .0 [110/1564] via 192.1.13.2, 00:00:09, Serial1/1
[110/1564] via 192.1.12.2, 00:00:09, Serial1/0
O E2 193.1.1.0/24 [110/5000] via 192.1.13.2, 00:00:09, Serial1/1
[110/5000] via 192.1.12.2, 00:00:09, Serial1/0
这里面还加入了VRRP、DHCP、Route-map等知识。希望对大家有所帮助！
