用Zebra做OSPF实验

OSPF（开放最短路径优先）路由协议是一项链路状态型技术，是目前IGP中应用最广、性能最优的一个 协议，解决了RIP不能解决的大型、可扩展的网络需求而写的，适用于大规模的网络。

Zebra支持OSPFv2和OSPFv3（用于IPv6的OSPF，CISCO还未对其封装），由于条件所限，下面的OSPF实 验同样是在两台单网卡的RedHat7.2下做的。

Zebra使用ospfd程序实现OSPF路由功能，但ospfd需要从zebra程序获得接口信息，所以zebra程序必须在 ospfd程序之前运行。ospfd不支持多个OSPF进程，我们不能指定OSPF进程号。

初始化第一台机器：

shell_1> cd /usr/local/etc
shell_1> cp zebra.conf.sample zebra.conf
shell_1> cp ospfd.conf.sample ospfd.conf
shell_1> zebra -d

进入zebra设置IP

shell_1> telnet localhost 2601
Password:
Router> en
Password:
Router# conf t
Router(config)# hostname r1
r1(config)# int eth0
r1(config-if)# ip address 192.168.5.121/24
r1(config-if)# ctrl+z
r1# copy run start

进入第一台机器的ospf设置

shell_1> ospfd -d
shell_1> telnet localhost 2604
Password:
ospfd> en
ospfd# conf t
ospfd(config)# hostname r1_ospfd !改个名字好辨认
r1_ospfd(config)# router ospf !启动ospf
r1_ospfd(config-router)# ospf router-id 192.168.5.121 !设置router-id
r1_ospfd(config-router)# network 192.168.5.0/24 area 0
!最关键的，来标识路由器上哪些IP网络号是OSPF的一部分，对于每个网络，我们必须标识该网络所属 的区域。由于我们只有两台机器，当然只有一个网络，所以只需执行一个network命令就够了。

对于我们的小网络，ospf就算配好了，下面来检验一下：

r1_ospfd(config-router)# ctrl+z
r1_ospfd# sh ip ospf route
============ OSPF network routing table ============
N 192.168.5.0/24 [10] area: 0.0.0.0
directly attached to eth0

============ OSPF router routing table =============

============ OSPF external routing table ===========

r1_ospfd# sh ip ospf database

OSPF Router with ID (192.168.5.121)

Router Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# CkSum Link count
192.168.5.121 192.168.5.121 126 0x80000002 0x8584 1

r1_ospfd# sh ip ospf int eth0
eth0 is up, line protocol is up

Internet Address 192.168.5.121/24, Area 0.0.0.0
Router ID 192.168.5.121, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.5.121, Interface Address 192.168.5.121
No backup designated router on this network
Timer intarvals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:07
Neighbor Count is 0, Adjacent neighbor count is 0

由于网络里没有其它的路由器，r1就把自己选为DR（指定路由器）了。Zebra对log处理可能有些问题，使 用log stdout不能显示各种debug信息，所以只能记录到文件，在shell下用tail命令查看。而且debug命令和 实际路由器也有不同。

r1_ospfd# debug ospf event
r1_ospfd(config)# log file /usr/local/etc/ospfd.log

然后我们在shell下查看debug信息

shell_1> tail -f /usr/local/etc/ospfd.log
--------------------------------8<---------------------------------------
2002/04/28 14:24:27 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 14:24:37 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 14:24:47 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 14:24:57 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 14:25:07 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
--------------------------------8<---------------------------------------

我们错过了最开始的信息，看到路由器每隔10秒发送一个hello数据包。hello数据包通过多目组播地址 224.0.0.5被发送出去，如果我们打开debug ospf packet all就能很清楚的看到。

第二台机器的设置

前面的初始化和第一台一样，不过这里名字设成r2便于辨认，IP设成了192.168.5.123/24。

进入第二台机器的ospf设置

shell_2> ospfd -d
shell_2> telnet localhost 2604
Password:
ospfd> en
ospfd# conf t
ospfd(config)# hostname r2_ospfd
r2_ospfd(config)# router ospf
r2_ospfd(config-router)# ospf router-id 192.168.5.123
r2_ospfd(config-router)# network 192.168.5.0/24 area 0

执行完network命令，我们看到第一台机器的tail -f /usr/local/etc/ospfd.log输出下面的信息：

--------------------------------8<---------------------------------------
2002/04/28 14:25:51 OSPF: Packet 192.168.5.123 [Hello:RECV]: Options *|*|-|-|-|-|E|*
2002/04/28 14:25:51 OSPF: NSM[eth0:192.168.5.121:0.0.0.0]: start
2002/04/28 14:25:52 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 14:25:52 OSPF: couldn't find any VL to associate the packet with
2002/04/28 14:25:52 OSPF: DR-Election[1st]: Backup 192.168.5.123
2002/04/28 14:25:52 OSPF: DR-Election[1st]: DR 192.168.5.121
2002/04/28 14:25:52 OSPF: Packet[DD]: Negotiation done (Slave).
--------------------------------8<---------------------------------------

r1收到r2(192.168.5.123)发过来的hello数据包，交换信息后选举DR，由于本身192.168.5.121是DR了，所以 只选举了BDR就好了。这时在r1上就能看到r2了。

r1_ospfd# sh ip ospf neig

Neighbor ID Pri State Dead Time Address Interface RXmtL RqstL DBsmL
192.168.5.123 1 Full/Backup 00:00:37 192.168.5.123 eth0:192.168.5.121 0 0 0

检验其它信息

r1_ospfd# sh ip ospf database

OSPF Router with ID (192.168.5.121)

Router Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# CkSum Link count
192.168.5.121 192.168.5.121 1259 0x80000008 0x534e 1
192.168.5.123 192.168.5.123 1265 0x80000006 0x534a 1

Net Link States (Area 0.0.0.0)

Link ID ADV Router Age Seq# CkSum
192.168.5.123 192.168.5.123 1265 0x80000001 0x5a5a

r1_ospfd# sh ip ospf int eth0
eth0 is up, line protocol is up

Internet Address 192.168.5.121/24, Area 0.0.0.0
Router ID 192.168.5.121, Network Type BROADCAST, Cost: 10
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 192.168.5.121, Interface Address 192.168.5.121
Backup Designated Router (ID) 192.168.5.123, Interface Address 192.168.5.123
Timer intarvals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
Hello due in 00:00:01
Neighbor Count is 1, Adjacent neighbor count is 1

和前面的输出信息相比，发生了很多变化，两台路由器已经相互识别了。OSPF不象RIP一样，每隔30秒 给所有的邻居广播一次完整的路由表，而是通过IP多目组播地址224.0.0.5每隔10秒发送一个很小的hello 数据包来维护邻居关系，当链路发生变化的时候，才重新计算。

拔掉两台机器连接的网线，看ospfd.log的记录：

--------------------------------8<---------------------------------------
2002/04/28 16:25:53 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 16:25:57 OSPF: Packet 192.168.5.123 [Hello:RECV]: Options *|*|-|-|-|-|E|*
2002/04/28 16:26:03 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 16:26:13 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 16:26:23 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 16:26:33 OSPF: make_hello: options: 2, int: eth0:192.168.5.121
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): Start
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): looked through areas
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): bb_configured: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): bb_act_attached: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): areas_configured: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): areas_act_attached: 1
2002/04/28 16:26:37 OSPF: nsm_change_status(): scheduling new router-LSA origination
2002/04/28 16:26:37 OSPF: DR-Election[1nd]: Backup 0.0.0.0
2002/04/28 16:26:37 OSPF: DR-Election[1nd]: DR 192.168.5.121
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): Start
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): looked through areas
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): bb_configured: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): bb_act_attached: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): areas_configured: 1
2002/04/28 16:26:37 OSPF: ospf_check_abr_status(): areas_act_attached: 1
2002/04/28 16:26:37 OSPF: Timer[router-LSA]: (router-LSA Refresh expire)
2002/04/28 16:26:37 OSPF: counting fully adjacent virtual neighbors in area 0.0.0.0
2002/04/28 16:26:37 OSPF: there are 0 of them
2002/04/28 16:26:37 OSPF: SPF: calculation timer scheduled
2002/04/28 16:26:37 OSPF: SPF: calculation timer delay = 5
2002/04/28 16:26:37 OSPF: ospf_flood_through_interface(): considering int eth0:192.168.5.121
2002/04/28 16:26:37 OSPF: ospf_flood_through_interface(): considering nbr 192.168.5.121
2002/04/28 16:26:42 OSPF: SPF: Timer (SPF calculation expire)
2002/04/28 16:26:42 OSPF: ospf_spf_calculate: Start
2002/04/28 16:26:42 OSPF: ospf_spf_calculate: running Dijkstra for area 0.0.0.0
2002/04/28 16:26:42 OSPF: SPF Result: 0 [R] 192.168.5.121
2002/04/28 16:26:42 OSPF: ========== OSPF routing table ==========
2002/04/28 16:26:42 OSPF: ========================================
2002/04/28 16:26:42 OSPF: ospf_process_stub():processing stubs for area 0.0.0.0
2002/04/28 16:26:42 OSPF: ospf_process_stub():processing router LSA, id: 192.168.5.121
2002/04/28 16:26:42 OSPF: ospf_process_stub(): we have 1 links to process
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): Start
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): processing route to 192.168.5.0/24
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): calculated cost is 0 + 10 = 10
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): installing new route
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): this network is on this router
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): the interface is eth0:192.168.5.121
2002/04/28 16:26:42 OSPF: ospf_intra_add_stub(): Stop
2002/04/28 16:26:42 OSPF: children of V:
2002/04/28 16:26:42 OSPF: ospf_spf_calculate: Stop
2002/04/28 16:26:42 OSPF: ospf_ia_routing():start
2002/04/28 16:26:42 OSPF: ospf_ia_routing():not ABR, considering all areas
2002/04/28 16:26:42 OSPF: Pruning unreachable networks
2002/04/28 16:26:42 OSPF: Pruning unreachable routers
2002/04/28 16:26:42 OSPF: Route: Router Routing Table free
2002/04/28 16:26:42 OSPF: SPF: calculation complete
--------------------------------8<---------------------------------------

我们看到r1生成一个LSA包，通知其它路由器，由于网络里只有自己了，又选自己为DR。r2也是一样。 我们再插上网线，查看ospfd.log：

--------------------------------8<---------------------------------------
2002/04/28 16:52:08 OSPF: Packet 192.168.5.123 [Hello:RECV]: Options *|*|-|-|-|-|E|*
2002/04/28 16:52:08 OSPF: NSM[eth0:192.168.5.121:0.0.0.0]: start
2002/04/28 16:52:08 OSPF: DR-Election[1st]: Backup 192.168.5.123
2002/04/28 16:52:08 OSPF: DR-Election[1st]: DR 192.168.5.121
2002/04/28 16:52:08 OSPF: DR-Election[1st]: Backup 0.0.0.0
2002/04/28 16:52:08 OSPF: DR-Election[1st]: DR 192.168.5.123
2002/04/28 16:52:08 OSPF: DR-Election[2nd]: Backup 192.168.5.121
2002/04/28 16:52:08 OSPF: DR-Election[2nd]: DR 192.168.5.123
--------------------------------8<---------------------------------------

由于拔了网线，r1和r2都把自己选为DR，一个网络只能有一个DR，所以恢复连接后它们重新进行了DR选 举，由于192.168.5.123的router id大，所以它被选为DR。

保存一下配置

r1_ospfd# copy run start
Configuration saved to /usr/local/etc/ospfd.conf
r2_ospfd# copy run start
Configuration saved to /usr/local/etc/ospfd.conf

以上只是演示了最简单的OSPF的配置，而OSPF在大型网络才广泛的使用，配置也复杂多很多。即使是 Zebra，也还可用做复杂的多的OSPF实验。