外部網關協議----BGP及實驗
- bgp的特點
- bgp協議特征
- bgp報文型別
- open報文
- update報文
- natification報文
- Keepalive報文
- route-refresh
- bgp的六種狀態
- idle
- conncet
- active
- opensent
- openconfirm
- established
- 兩種bgp
- ibgp的水平分割
- bgp的兩張表
- bgp鄰居表
- bgp路由表
- bgp路由通告規則
- 實驗
bgp的特點
1.能夠承載大批量的路由資訊，能夠支撐大規模網路
2.不能自己發現鄰居
3.不能自己發現路由資訊
bgp協議特征
基于tcp，埠號179
1.運行bgp的路由器稱為bgp發言者
2.兩個建立bgp會話的路由器互為對等體
3.bgp路由器只發送增量的bgp路由更新，或進行觸發更新（不會周期性更新）
4.能夠承載大批量的路由前綴，用于大規模網路
bgp報文型別
open報文
建立鄰居關系 ，先建立tcp連接，成功后向對等體發送open報文
update報文
用于發送bgp路由資訊，連接建立后，發送路由或路由發生變化時，發送update通告對端
natification報文
報告錯誤，中止對等體關系，bgp在運行中發現錯誤時，發送此報文通告對方
Keepalive報文
維持bgp對等體關系，定時發送此報文以保持bgp對等體關系，默認60s，死亡時間是180s
route-refresh
改變路由策略后請求對等體重新發送路由資訊，當理由策略發生變化后，觸發請求對等體重新通告路由
bgp的六種狀態
idle
嘗試建立tcp連接，開始準備tcp連接
conncet
發tcp包，正在進行tcp連接，失敗進入active，反復嘗試連接，成功進入opensent
active
發tcp包，tcp連接沒成功，反復嘗試連接
opensent
發open包，tcp連接成功，開始發open包，攜帶引數協商對等體的建立
openconfirm
發Keepalive包，協商成功，自己發送Keepalive包，等待對方的Keepalive包
established
發update包，收到對方的Keepalive，對等體建立成功
兩種bgp
一種是ibgp，在同一個as區域里面的bgp路由
一種是ebgp，跨越不同as區域的bgp路由
ibgp的水平分割
路由器不能將自己從ibgp對等體學到的路由再傳遞給其他的ibgp對等體
bgp的兩張表
bgp鄰居表
記錄bgp對等體的表，查看命令dis bgp peer
bgp路由表
記錄bgp路由的表，查看命令dis bgp routing
bgp路由通告規則
①bgp只把最優路由傳給對等體
②路由器從ebgp對等體獲得的路由傳遞給所有的bgp對等體
③路由器從ibgp對等體獲得的路由不會傳遞給它的bgp對等體
④路由器從ibgp對等體獲得的路由是否通告給ebgp對等體要視igp和bgp同步情況決定
實驗
首先配置所以路由器的IP地址，在如圖所說的區域創建ospf協議和rip協議
<R1>
#
ospf 1 router-id 1.1.1.1
area 0.0.0.0
network 1.1.1.1 0.0.0.0
network 12.0.0.0 0.0.0.255
network 15.0.0.0 0.0.0.255
<R2>
#
ospf 1 router-id 2.2.2.2
area 0.0.0.0
network 2.2.2.2 0.0.0.0
network 12.0.0.0 0.0.0.255
#
rip 1
version 2
network 23.0.0.0
<R3>
#
rip 1
version 2
network 23.0.0.0
network 3.0.0.0
#
<R5>
#
ospf 1 router-id 5.5.5.5
area 0.0.0.0
network 5.5.5.5 0.0.0.0
network 15.0.0.0 0.0.0.255
能看到鄰居已經建立
<R1>
Please check whether system data has been changed, and save data in time
Configuration console time out, please press any key to log on
<R1>dis ospf pee
OSPF Process 1 with Router ID 1.1.1.1
Neighbors
Area 0.0.0.0 interface 12.0.0.1(GigabitEthernet0/0/0)'s neighbors
Router ID: 2.2.2.2 Address: 12.0.0.2
State: Full Mode:Nbr is Master Priority: 1
DR: 12.0.0.2 BDR: 12.0.0.1 MTU: 0
Dead timer due in 31 sec
Retrans timer interval: 5
Neighbor is up for 00:13:17
Authentication Sequence: [ 0 ]
Neighbors
Area 0.0.0.0 interface 15.0.0.1(GigabitEthernet0/0/1)'s neighbors
Router ID: 5.5.5.5 Address: 15.0.0.2
State: Full Mode:Nbr is Master Priority: 1
DR: 15.0.0.2 BDR: 15.0.0.1 MTU: 0
Dead timer due in 37 sec
Retrans timer interval: 5
Neighbor is up for 00:13:18
Authentication Sequence: [ 0 ]
<R1>
然后R1，R2，R5互相建立ibgp鄰居，R2，R3互相建立ebgp鄰居
<R5>
#
bgp 100
router-id 5.5.5.5
peer 1.1.1.1 as-number 100
peer 1.1.1.1 connect-interface LoopBack0
peer 2.2.2.2 as-number 100
#
ipv4-family unicast
undo synchronization
network 202.0.0.0
network 202.0.1.0
peer 1.1.1.1 enable
peer 2.2.2.2 enable
<R1>
#
bgp 100
router-id 1.1.1.1
peer 2.2.2.2 as-number 100
peer 2.2.2.2 connect-interface LoopBack0
peer 5.5.5.5 as-number 100
peer 5.5.5.5 connect-interface LoopBack0
#
<R2>
#
bgp 100
router-id 2.2.2.2
peer 1.1.1.1 as-number 100
peer 1.1.1.1 connect-interface LoopBack0
peer 5.5.5.5 as-number 100
peer 5.5.5.5 connect-interface LoopBack0
peer 23.0.0.2 as-number 200
#
<R3>
#
bgp 200
router-id 3.3.3.3
peer 23.0.0.1 as-number 100
能看到鄰居已經建立
<R2>dis bgp peer
BGP local router ID : 2.2.2.2
Local AS number : 100
Total number of peers : 3 Peers in established state : 3
Peer V AS MsgRcvd MsgSent OutQ Up/Down State Pre
fRcv
1.1.1.1 4 100 16 22 0 00:14:11 Established
0
5.5.5.5 4 100 18 22 0 00:14:11 Established
2
23.0.0.2 4 200 17 24 0 00:14:41 Established
1
<R2>
然后將202.0.0.1和202.0.1.1的路由寫進bgp路由表，
[R5-bgp]dis th
[V200R003C00]
#
bgp 100
router-id 5.5.5.5
peer 1.1.1.1 as-number 100
peer 1.1.1.1 connect-interface LoopBack0
peer 2.2.2.2 as-number 100
#
ipv4-family unicast
undo synchronization
network 202.0.0.0
network 202.0.1.0
peer 1.1.1.1 enable
peer 2.2.2.2 enable
#
return
將ospf注入bgp協議中并將R2與R3相連的網段直連寫進bgp路由表，然后修改R5到R3的bgp下一跳介面
import-route ospf 1
peer 1.1.1.1 enable
peer 1.1.1.1 next-hop-local
peer 5.5.5.5 enable
peer 23.0.0.2 enable
此時R3可以ping通202.0.0.1和202.0.1.1的主機
<R3>ping -a 3.3.3.3 202.0.0.1
PING 202.0.0.1: 56 data bytes, press CTRL_C to break
Reply from 202.0.0.1: bytes=56 Sequence=1 ttl=253 time=60 ms
Reply from 202.0.0.1: bytes=56 Sequence=2 ttl=253 time=40 ms
Reply from 202.0.0.1: bytes=56 Sequence=3 ttl=253 time=30 ms
Reply from 202.0.0.1: bytes=56 Sequence=4 ttl=253 time=30 ms
Reply from 202.0.0.1: bytes=56 Sequence=5 ttl=253 time=30 ms
--- 202.0.0.1 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 30/38/60 ms
<R3>ping -a 3.3.3.3 202.0.1.1
PING 202.0.1.1: 56 data bytes, press CTRL_C to break
Reply from 202.0.1.1: bytes=56 Sequence=1 ttl=253 time=40 ms
Reply from 202.0.1.1: bytes=56 Sequence=2 ttl=253 time=30 ms
Reply from 202.0.1.1: bytes=56 Sequence=3 ttl=253 time=30 ms
Reply from 202.0.1.1: bytes=56 Sequence=4 ttl=253 time=40 ms
Reply from 202.0.1.1: bytes=56 Sequence=5 ttl=253 time=40 ms
--- 202.0.1.1 ping statistics ---
5 packet(s) transmitted
5 packet(s) received
0.00% packet loss
round-trip min/avg/max = 30/36/40 ms
<R3>
并且路由條目是ebgp
<R3>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 15 Routes : 15
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 EBGP 255 1 D 23.0.0.1 GigabitEthernet
0/0/0
2.2.2.2/32 EBGP 255 0 D 23.0.0.1 GigabitEthernet
0/0/0
3.3.3.3/32 Direct 0 0 D 127.0.0.1 LoopBack0
5.5.5.5/32 EBGP 255 2 D 23.0.0.1 GigabitEthernet
0/0/0
12.0.0.0/30 EBGP 255 0 D 23.0.0.1 GigabitEthernet
0/0/0
15.0.0.0/30 EBGP 255 2 D 23.0.0.1 GigabitEthernet
0/0/0
23.0.0.0/30 Direct 0 0 D 23.0.0.2 GigabitEthernet
0/0/0
23.0.0.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
23.0.0.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
202.0.0.0/24 EBGP 255 0 D 23.0.0.1 GigabitEthernet
0/0/0
202.0.1.0/24 EBGP 255 0 D 23.0.0.1 GigabitEthernet
0/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R3>
在R2上看202.0.0.1和202.0.1.1的主機路由條目是ibgp
<R2>dis ip ro
Route Flags: R - relay, D - download to fib
------------------------------------------------------------------------------
Routing Tables: Public
Destinations : 17 Routes : 17
Destination/Mask Proto Pre Cost Flags NextHop Interface
1.1.1.1/32 OSPF 10 1 D 12.0.0.1 GigabitEthernet
0/0/0
2.2.2.2/32 Direct 0 0 D 127.0.0.1 LoopBack0
3.3.3.3/32 RIP 100 1 D 23.0.0.2 GigabitEthernet
0/0/1
5.5.5.5/32 OSPF 10 2 D 12.0.0.1 GigabitEthernet
0/0/0
12.0.0.0/30 Direct 0 0 D 12.0.0.2 GigabitEthernet
0/0/0
12.0.0.2/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
12.0.0.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/0
15.0.0.0/30 OSPF 10 2 D 12.0.0.1 GigabitEthernet
0/0/0
23.0.0.0/30 Direct 0 0 D 23.0.0.1 GigabitEthernet
0/0/1
23.0.0.1/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
23.0.0.3/32 Direct 0 0 D 127.0.0.1 GigabitEthernet
0/0/1
127.0.0.0/8 Direct 0 0 D 127.0.0.1 InLoopBack0
127.0.0.1/32 Direct 0 0 D 127.0.0.1 InLoopBack0
127.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
202.0.0.0/24 IBGP 255 0 RD 5.5.5.5 GigabitEthernet
0/0/0
202.0.1.0/24 IBGP 255 0 RD 5.5.5.5 GigabitEthernet
0/0/0
255.255.255.255/32 Direct 0 0 D 127.0.0.1 InLoopBack0
<R2>
總結：bgp協議的鄰居和路由條目都必須手動進行操作，自己本身不能發現鄰居和路由
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