mrgwy

BGP邻居建立与路由发布

一、实验拓扑

图片24.png

二、实验配置

1、建立BGP邻居

router ospf 1

router-id 10.10.0.2

log-adjacency-changes

redistribute connected metric 1000 metric-type 1 subnets

network 10.10.0.2 0.0.0.0 area 0

network 10.10.1.0 0.0.0.3 area 0

network 10.10.1.4 0.0.0.3 area 0

default-information originate always metric 2000 metric-type 1

router ospf 1

router-id 10.10.0.5

log-adjacency-changes

passive-interface Serial0/0

network 10.10.0.5 0.0.0.0 area 0

network 10.10.1.0 0.0.0.3 area 0

network 10.10.1.8 0.0.0.3 area 0

network 10.20.45.0 0.0.0.3 area 0

default-information originate always metric 2000 metric-type 1

注意：如果AS边界接口启动了IGP，必须配置被动接口；禁止在AS间建立IGP邻居，禁止将AS内部IGP拓扑通告给其他AS，AS间的路由传播通过BGP。

R2#sh ip bgp summary

BGP router identifier 10.10.0.2, local AS number 10

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

10.10.0.5 4 10 7 7 1 0 0 00:03:22 0

10.10.23.2 4 30 6 6 1 0 0 00:02:05 0

R2#

R2#sh ip bgp neighbors

BGP neighbor is 10.10.0.5, remote AS 10, internal link

BGP version 4, remote router ID 10.10.0.5

BGP state = Established, up for 00:04:42

Last read 00:00:42, last write 00:00:43, hold time is 180, keepalive interval is 60 seconds

Neighbor capabilities:

Route refresh: advertised and received(old & new)

Address family IPv4 Unicast: advertised and received

Message statistics:

InQ depth is 0

OutQ depth is 0

Sent Rcvd

Opens: 1 1

Notifications: 0 0

Updates: 0 0

Keepalives: 7 7

Route Refresh: 0 0

Total: 8 8

Default minimum time between advertisement runs is 0 seconds

For address family: IPv4 Unicast

BGP table version 1, neighbor version 1/0

Output queue size : 0

Index 1, Offset 0, Mask 0x2

1 update-group member

Sent Rcvd

Prefix activity: ---- ----

Prefixes Current: 0 0

Prefixes Total: 0 0

Implicit Withdraw: 0 0

Explicit Withdraw: 0 0

Used as bestpath: n/a 0

Used as multipath: n/a 0

Outbound Inbound

Local Policy Denied Prefixes: -------- -------

Total: 0 0

Number of NLRIs in the update sent: max 0, min 0

Connections established 1; dropped 0

Last reset never

Connection state is ESTAB, I/O status: 1, unread input bytes: 0

Connection is ECN Disabled, Mininum incoming TTL 0, Outgoing TTL 255

Local host: 10.10.0.2, Local port: 24133

Foreign host: 10.10.0.5, Foreign port: 179

Enqueued packets for retransmit: 0, input: 0 mis-ordered: 0 (0 bytes)

Event Timers (current time is 0x64B654):

Timer Starts Wakeups Next

Retrans 7 0 0x0

TimeWait 0 0 0x0

AckHold 6 5 0x0

SendWnd 0 0 0x0

KeepAlive 0 0 0x0

GiveUp 0 0 0x0

PmtuAger 0 0 0x0

DeadWait 0 0 0x0

iss: 3435368555 snduna: 3435368734 sndnxt: 3435368734 sndwnd: 16206

irs: 2674832881 rcvnxt: 2674833060 rcvwnd: 16206 delrcvwnd: 178

SRTT: 264 ms, RTTO: 1169 ms, RTV: 905 ms, KRTT: 0 ms

minRTT: 140 ms, maxRTT: 860 ms, ACK hold: 200 ms

Flags: active open, nagle

IP Precedence value : 6

Datagrams (max data segment is 536 bytes):

Rcvd: 11 (out of order: 0), with data: 6, total data bytes: 178

Sent: 14 (retransmit: 0, fastretransmit: 0, partialack: 0, Second Congestion: 0), with data: 7, total data bytes: 178

BGP neighbor is 10.10.23.2, remote AS 30, external link

BGP version 4, remote router ID 10.10.0.3

BGP state = Established, up for 00:03:33

..........

R3#sh ip bgp summary

BGP router identifier 10.10.0.3, local AS number 30

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

10.10.23.1 4 10 9 9 1 0 0 00:05:35 0

10.30.34.2 4 40 6 7 1 0 0 00:03:50 0

R4#sh ip bgp summary

BGP router identifier 10.10.0.4, local AS number 40

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

10.20.45.1 4 10 0 0 0 0 0 never Idle //TCP建立不成功

10.30.34.1 4 30 9 8 1 0 0 00:05:24 0

R4#

R5#sh ip bgp summary

BGP router identifier 10.10.0.5, local AS number 10

BGP table version is 1, main routing table version 1

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

10.10.0.2 4 10 12 12 1 0 0 00:08:35 0

10.20.24.2 4 40 0 0 0 0 0 never Idle//注意没有建立邻居

TCP建立不成功，这里的原因是配错IP

我们查看一下R5的BGP配置

router bgp 10

no synchronization

bgp log-neighbor-changes

network 10.10.0.0 mask 255.255.0.0

neighbor 10.10.0.2 remote-as 10

neighbor 10.10.0.2 update-source Loopback0

neighbor 10.20.24.2 remote-as 40 //错误所在低级错误

no auto-summary

我们改正过来

R5(config)#router bgp 10

R5(config-router)#no neighbor 10.20.24.2 remote-as 40

R5(config-router)#nei 10.20.45.2 remote-as 40

R5#sh ip bgp sum

BGP router identifier 10.10.0.5, local AS number 10

BGP table version is 13, main routing table version 12

3 network entries using 351 bytes of memory

6 path entries using 312 bytes of memory

7/3 BGP path/bestpath attribute entries using 868 bytes of memory

4 BGP AS-PATH entries using 96 bytes of memory

0 BGP route-map cache entries using 0 bytes of memory

0 BGP filter-list cache entries using 0 bytes of memory

BGP using 1627 total bytes of memory

BGP activity 6/3 prefixes, 10/4 paths, scan interval 60 secs

Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd

10.10.0.2 4 10 82 81 12 0 0 01:17:12 3

10.20.45.2 4 40 7 2 0 0 0 00:00:00 2

建立成功！！

2、BGP配置及调试（路由发布：静态注入）

R2(config)#ip route 10.10.0.0 255.255.0.0 null 0 //配置了一条静态路由

R2(config)#router bgp 10

R2(config-router)#net 10.10.0.0 mask 255.255.0.0 //注入这条静态路由

R2(config-router)#end

*Mar 1 02:16:13.491: %SYS-5-CONFIG_I: Configured from console by console

R2#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

10.0.0.0/8 is variably subnetted, 11 subnets, 4 masks

S 10.10.0.0/16 is directly connected, Null0

C 10.10.1.0/30 is directly connected, Ethernet1/0

O 10.10.0.1/32 [110/101] via 10.10.1.6, 00:37:53, Serial0/0

C 10.10.0.2/32 is directly connected, Loopback0

O 10.10.5.0/24 [110/110] via 10.10.1.6, 00:37:53, Serial0/0

C 10.10.1.4/30 is directly connected, Serial0/0

O 10.10.0.5/32 [110/101] via 10.10.1.2, 00:37:53, Ethernet1/0

O 10.10.0.6/32 [110/201] via 10.10.1.2, 00:37:53, Ethernet1/0

O 10.10.1.8/30 [110/200] via 10.10.1.2, 00:37:53, Ethernet1/0

O 10.10.1.12/30 [110/200] via 10.10.1.6, 00:37:53, Serial0/0

C 10.10.23.0/30 is directly connected, Serial0/1

R2#sh ip bgp

BGP table version is 2, local router ID is 10.10.0.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete //BGP的属性：源头

Network Next Hop Metric LocPrf Weight Path

*> 10.10.0.0/16 0.0.0.0 0 32768 i //这里的i表示IGP

注意：weight是cisco的私有值，不是BGP属性，不能在BGP邻居间传播，只在BGP本路由器内有效。Cisco里首选weight值最高的路由。

R5(config)# ip route 10.10.0.0 255.255.0.0 null 0

R5(config)#router bgp 10

R5(config-router)#net 10.10.0.0 mask 255.255.0.0

注意：R5上发布这条路由是为了备份

R3(config)#ip route 10.30.0.0 255.255.0.0 null 0

R3(config)#router bgp 30

R3(config-router)#net 10.30.0.0 mask 255.255.0.0

R4(config)#ip route 10.40.0.0 255.255.0.0 null 0

R4(config)#router bgp 40

R4(config-router)#net 10.40.0.0 mask 255.255.0.0

查看各设备BGP表

R2#sh ip bgp

BGP table version is 13, local router ID is 10.10.0.2

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* i10.10.0.0/16 10.10.0.5 0 100 0 i //从IBGP邻居学到的？

*> 0.0.0.0 0 32768 i //静态注入的IGP

*> 10.30.0.0/16 10.10.23.2 0 0 30 i

*>i10.40.0.0/16 10.20.45.2 0 100 0 40 i //不会改变下一跳？

* 10.10.23.2 0 30 40 i

问题：什么叫IGP？从IBGP邻居学到的为什么也是i? （这里的i是指path那里的标记）

解答：i是表示该路由在来源路由器那里是IGP。（来源路由器指最先发起该条路由的路由器）

* i10.10.0.0/16

最前面的i是指该路由是内部路由，即从IBGP学来的BGP路由。

R5#sh ip bgp

BGP table version is 13, local router ID is 10.10.0.5

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* i10.10.0.0/16 10.10.0.2 0 100 0 i //

*> 0.0.0.0 0 32768 i

* 10.30.0.0/16 10.20.45.2 0 40 30 i

*>i 10.10.23.2 0 100 0 30 i

*> 10.40.0.0/16 10.20.45.2 0 0 40 i

//cisco首选weight值最高的路由；其他厂家，选择本地始发的路由

本地始发的路由下一跳0.0.0.0，向BGP邻居通告时，将下一跳改为自己。

//选择AS-PATH最短的路由

BGP只把最优的路由通告给它的邻居，以及基于邻居的水平分割。

上面R2将10.30.0.0传给IBGP邻居R5时不改变下一跳。

R3#sh ip bgp

BGP table version is 12, local router ID is 10.10.0.3

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

* 10.10.0.0/16 10.30.34.2 0 40 10 i

*> 10.10.23.1 0 0 10 i

*> 10.30.0.0/16 0.0.0.0 0 32768 i //本地始发路由

* 10.40.0.0/16 10.10.23.1 0 10 40 i

*> 10.30.34.2 0 0 40 i

R4#sh ip bgp

BGP table version is 21, local router ID is 10.10.0.4

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete

Network Next Hop Metric LocPrf Weight Path

*> 10.10.0.0/16 10.20.45.1 0 0 10 i

* 10.30.34.1 0 30 10 i

* 10.30.0.0/16 10.20.45.1 0 10 30 i//下一跳改为自己

*> 10.30.34.1 0 0 30 i

*> 10.40.0.0/16 0.0.0.0 0 32768 i

上面R3与R4：R3的本地始发路由下一跳为0.0.0.0 ，向BGP邻居R4通告时，将下一跳改为自己.

查看个设备的全局路由表

R3>en

R3#sh ip route

10.0.0.0/8 is variably subnetted, 7 subnets, 4 masks

B 10.10.0.0/16 [20/0] via 10.10.23.1, 01:20:27

C 10.10.0.3/32 is directly connected, Loopback0

S 10.30.0.0/16 is directly connected, Null0

C 10.30.3.0/24 is directly connected, Ethernet1/1

C 10.10.23.0/30 is directly connected, Serial0/0

B 10.40.0.0/16 [20/0] via 10.30.34.2, 00:00:03

C 10.30.34.0/30 is directly connected, Serial0/1

10.0.0.0/8 is variably subnetted, 7 subnets, 4 masks

B 10.10.0.0/16 [20/0] via 10.20.45.1, 00:17:49 //邻居的静态注入

C 10.10.0.4/32 is directly connected, Loopback0

B 10.30.0.0/16 [20/0] via 10.20.45.1, 00:01:00 //邻居的静态注入

S 10.40.0.0/16 is directly connected, Null0 自己的静态路由管理距离是0

C 10.40.4.0/24 is directly connected, Ethernet1/1

C 10.20.45.0/30 is directly connected, Serial0/1

C 10.30.34.0/30 is directly connected, Serial0/0

注意：不同类型的路由协议优选原则按照管理距离

而BGP自己的路由优选原则是根据那几个属性，不要混淆了。。

10.0.0.0/8 is variably subnetted, 11 subnets, 3 masks

S 10.10.0.0/16 is directly connected, Null0 //优选管理距离小的静态路由

C 10.10.1.0/30 is directly connected, Ethernet1/0

C 10.10.0.2/32 is directly connected, Loopback0

O 10.10.0.5/32 [110/101] via 10.10.1.2, 00:00:03, Ethernet1/0 //IGP

O 10.10.0.6/32 [110/201] via 10.10.1.2, 00:00:03, Ethernet1/0

O 10.10.1.8/30 [110/200] via 10.10.1.2, 00:00:03, Ethernet1/0

O 10.10.1.12/30 [110/210] via 10.10.1.2, 00:00:03, Ethernet1/0

B 10.30.0.0/16 [20/0] via 10.10.23.2, 01:22:20

C 10.10.23.0/30 is directly connected, Serial0/1

B 10.40.0.0/16 [200/0] via 10.20.45.2, 00:16:09

O 10.20.45.0/30 [110/164] via 10.10.1.2, 00:00:03, Ethernet1/0 //递归查找

10.0.0.0/8 is variably subnetted, 11 subnets, 3 masks

S 10.10.0.0/16 is directly connected, Null0

C 10.10.1.0/30 is directly connected, Ethernet1/0

O 10.10.0.2/32 [110/101] via 10.10.1.1, 00:00:02, Ethernet1/0

C 10.10.0.5/32 is directly connected, Loopback0

O 10.10.0.6/32 [110/101] via 10.10.1.10, 00:00:02, Serial0/1

C 10.10.1.8/30 is directly connected, Serial0/1

O 10.10.1.12/30 [110/110] via 10.10.1.10, 00:00:02, Serial0/1

B 10.30.0.0/16 [200/0] via 10.10.23.2, 01:32:36

O E1 10.10.23.0/30 [110/1100] via 10.10.1.1, 00:00:02, Ethernet1/0//从R2学来的通过重发布进来OSPF进程的直连路由

B 10.40.0.0/16 [20/0] via 10.20.45.2, 00:17:57

C 10.20.45.0/30 is directly connected, Serial0/0

10.0.0.0/8 is variably subnetted, 11 subnets, 3 masks

O 10.10.1.0/30 [110/200] via 10.10.1.5, 00:00:31, Serial0/1

C 10.10.0.1/32 is directly connected, Loopback0

O 10.10.0.2/32 [110/101] via 10.10.1.5, 00:00:31, Serial0/1

C 10.10.5.0/24 is directly connected, Ethernet1/1

C 10.10.1.4/30 is directly connected, Serial0/1

O 10.10.0.5/32 [110/201] via 10.10.1.5, 00:00:31, Serial0/1

O 10.10.0.6/32 [110/301] via 10.10.1.5, 00:00:31, Serial0/1

O 10.10.1.8/30 [110/300] via 10.10.1.5, 00:00:31, Serial0/1

C 10.10.1.12/30 is directly connected, Ethernet1/0

O E1 10.10.23.0/30 [110/1100] via 10.10.1.5, 00:00:31, Serial0/1

O 10.20.45.0/30 [110/264] via 10.10.1.5, 00:00:31, Serial0/1

O*E1 0.0.0.0/0 [110/2100] via 10.10.1.5, 00:00:31, Serial0/1//从R5学到的重发布缺省

1）R2与R1之间的链路为什么在数据链路层上是一下子up一下子down呢？以致导致学到的这条路由是从R5来的？

2）注意：R1没有收到BGP路由是因为，运行BGP的路由器只会把自己的BGP路由表发给自己的BGP邻居。

10.0.0.0/8 is variably subnetted, 12 subnets, 3 masks

O 10.10.1.0/30 [110/200] via 10.10.1.9, 00:00:23, Serial0/0

O 10.10.0.1/32 [110/301] via 10.10.1.9, 00:00:23, Serial0/0

O 10.10.0.2/32 [110/201] via 10.10.1.9, 00:00:23, Serial0/0

O 10.10.5.0/24 [110/310] via 10.10.1.9, 00:00:23, Serial0/0

O 10.10.1.4/30 [110/300] via 10.10.1.9, 00:00:23, Serial0/0

O 10.10.0.5/32 [110/101] via 10.10.1.9, 00:00:23, Serial0/0

C 10.10.6.0/24 is directly connected, Ethernet1/1

C 10.10.0.6/32 is directly connected, Loopback0

C 10.10.1.8/30 is directly connected, Serial0/0

C 10.10.1.12/30 is directly connected, Ethernet1/0

O E1 10.10.23.0/30 [110/1200] via 10.10.1.9, 00:00:23, Serial0/0

O 10.20.45.0/30 [110/164] via 10.10.1.9, 00:00:23, Serial0/0

O*E1 0.0.0.0/0 [110/2100] via 10.10.1.9, 00:00:24, Serial0/0