Cisco MIBGP MPLS ×××配置指導
1 BGP/MPLS ×××概述
BGP/MPLS ×××是一種三層×××技術,該技術使用MBGP在骨幹網絡發佈×××V4路由,使用MPLS在骨幹網上轉發×××報文。三層×××一般部署在運營商或者大型企業網內部,因爲其可以比較方便的支持MPLS QoS和TE技術,所以做爲企業DCN網絡的基本模型獲得愈來愈普遍的應用。
本文主要提供Cisco設備自治系統內的三層×××配置,並對關鍵點進行簡單分析。
2 一些基本概念
如上圖,整個三層×××網絡主要由CE、PE和P設備這三部分組成;圖中的R1和R5爲CE設備,即用戶網絡邊緣設備,能夠是一個用戶網絡,也能夠是一臺路由器,也能夠是一臺用戶主機,對於CE而言,CE感知不到×××的存在,也不須要支持MPLS功能,做爲CE,它與PE直連,只須要支持普通IP便可,與PE互通的網絡協議能夠是EBGP、多實例的IGP或者靜態路由,這個是具體狀況而言,本文的配置採用EBGP鏈接PE和CE;圖中的R2和R4爲PE設備,即服務提供商邊緣設備,與CE直連,在三層×××網絡中,對於×××的處理都發生在PE上;圖中的R3爲P設備,即整個網絡中的骨幹路由器,不與CE直連,P能夠和PE鏈接,也能夠和P鏈接,固然也能夠不存在,即整個三層×××網絡中只有PE設備,沒有P設備,對於P而言,只須要具備基本的MPLS轉發能力便可。
RD:Route Distinguisher,RD 用於發佈×××路由時區分使用相同地址的IPv4 前綴,好比兩個不一樣的×××均有相同的IPv4前綴,若是不加以區分的話,就不可以正常的經過BGP發佈給鄰居,這裏經過RD和普通的IPv4前綴造成一個新的×××V4的地址,而後經過MBGP發佈給對端鄰居,從而區分不一樣×××中的相同地址,這樣就能夠實現三層×××中地址重疊這一功能。須要注意的是必須保證RD值全局惟一,即不一樣的×××設置不一樣的RD。具體的RD格式這裏不做詳細描述。
RT:Route Target,RT是一種BGP擴展團體屬性,用來控制××× 路由信息的發佈。因爲RD不能用於判斷某條路由的發起者,也不能判斷某條路由屬於哪一個×××。這時就須要用到RT,RT用來描述一條×××v4路由能夠爲哪些×××所接收,以及PE能夠接收哪些×××發送來的路由。
3 網絡分析
R二、R3和R4之間部署IGP和LDP,R2和R4之間創建MIBG鄰居;
R1和R二、R4和R5之間分別創建普通EBGP鄰居;
R2和R4上配置vrf,將其與R1和R5直連的鏈路配置屬於該vrf。
4 數據設計
Loopback地址:202.1.1.X/32,X=一、二、三、四、5,即路由器序號;
接口地址:80.X.Y.Z/24,X/Y=路由器序號,Z=一、2,路由器序號小的爲1,大的爲2;
IGP:PE-P-PE之間部署OSPF和LDP;
AS:R2和R4的AS號爲100,R1的AS號爲1000,R5的AS號爲5000;
Vrf:RT爲100:1,RD爲100:1。
5 配置步驟
配置LSR的各接口地址;
配置OSPF保證LSR之間可達;
配置MPLS基本能力;
配置MIBGP和EBGP;
配置vrf以及相應的RD、RT。
6 詳細配置
爲了節約版本,只羅列出5臺路由器的相關配置,其餘無關配置均不貼出來。
[R1]
R1#show run
!
version 12.4
!
hostname R1
!
ip cef
!
no mpls ip
!
interface Loopback0
ip address 202.1.1.1 255.255.255.255
!
interface Ethernet4/0
ip address 80.1.2.1 255.255.255.0
duplex full
!
router bgp 1000
no synchronization
bgp log-neighbor-changes
redistribute connected
neighbor 80.1.2.2 remote-as 100
no auto-summary
!
end
[R2]
R2#show run
!
version 12.4
!
hostname R2
!
ip cef
!
ip vrf vrf1
rd 100:1
route-target export 100:1
route-target import 100:1
!
interface Loopback0
ip address 202.1.1.2 255.255.255.255
!
interface Ethernet4/0
ip vrf forwarding vrf1
ip address 80.1.2.2 255.255.255.0
duplex full
!
interface Ethernet4/1
ip address 80.2.3.1 255.255.255.0
duplex full
mpls ip
!
router ospf 1
log-adjacency-changes
network 80.1.2.0 0.0.0.255 area 0
network 80.2.3.0 0.0.0.255 area 0
network 202.1.1.2 0.0.0.0 area 0
!
router bgp 100
bgp log-neighbor-changes
neighbor 202.1.1.4 remote-as 100
neighbor 202.1.1.4 update-source Loopback0
!
address-family ipv4
no neighbor 202.1.1.4 activate
no auto-summary
no synchronization
exit-address-family
!
address-family ***v4
neighbor 202.1.1.4 activate
neighbor 202.1.1.4 send-community extended
exit-address-family
!
address-family ipv4 vrf vrf1
redistribute connected
neighbor 80.1.2.1 remote-as 1000
neighbor 80.1.2.1 activate
no synchronization
exit-address-family
!
end
[R3]
R3#show run
!
version 12.4
!
hostname R3
!
ip cef
!
interface Loopback0
ip address 202.1.1.3 255.255.255.255
!
interface Ethernet4/1
ip address 80.2.3.2 255.255.255.0
duplex full
mpls ip
!
interface Ethernet4/2
ip address 80.3.4.1 255.255.255.0
duplex half
mpls ip
!
router ospf 1
log-adjacency-changes
network 80.1.3.0 0.0.0.255 area 0
network 80.2.3.0 0.0.0.255 area 0
network 80.3.4.0 0.0.0.255 area 0
network 202.1.1.3 0.0.0.0 area 0
!
end
[R4]
R4#show run
!
version 12.4
!
hostname R4
!
ip cef
!
ip vrf vrf1
rd 100:1
route-target export 100:1
route-target import 100:1
!
interface Loopback0
ip address 202.1.1.4 255.255.255.255
!
interface Ethernet4/2
ip address 80.3.4.2 255.255.255.0
duplex half
mpls ip
!
interface Ethernet4/3
ip vrf forwarding vrf1
ip address 80.4.5.1 255.255.255.0
duplex half
!
router ospf 1
log-adjacency-changes
network 80.3.4.0 0.0.0.255 area 0
network 80.4.5.0 0.0.0.255 area 0
network 202.1.1.4 0.0.0.0 area 0
!
router bgp 100
bgp log-neighbor-changes
neighbor 202.1.1.2 remote-as 100
neighbor 202.1.1.2 update-source Loopback0
!
address-family ipv4
no neighbor 202.1.1.2 activate
no auto-summary
no synchronization
exit-address-family
!
address-family ***v4
neighbor 202.1.1.2 activate
neighbor 202.1.1.2 send-community extended
exit-address-family
!
address-family ipv4 vrf vrf1
neighbor 80.4.5.2 remote-as 5000
neighbor 80.4.5.2 activate
no synchronization
exit-address-family
!
end
[R5]
R5#
R5#show run
!
version 12.4
!
hostname R5
!
ip cef
!
no mpls ip
!
interface Loopback0
ip address 202.1.1.5 255.255.255.255
!
interface Ethernet4/3
ip address 80.4.5.2 255.255.255.0
duplex half
!
router bgp 5000
no synchronization
bgp log-neighbor-changes
redistribute connected
neighbor 80.4.5.1 remote-as 100
no auto-summary
!
end
R5#
7 顯示信息
BGP
鄰居的創建
在R2上顯示BGP鄰居能夠看出,R2和R1創建EBGP鄰居,和R4創建MIBGP鄰居:
R2#show bgp ***v4 unicast all neighbors
BGP neighbor is 80.1.2.1, vrf vrf1, remote AS 1000, external link
BGP version 4, remote router ID 202.1.1.1
BGP state = Established, up for 00:57:54
Last read 00:00:55, last write 00:00:55, 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
BGP neighbor is 202.1.1.4, remote AS 100, internal link
BGP version 4, remote router ID 202.1.1.4
BGP state = Established, up for 00:56:46
Last read 00:00:46, last write 00:00:46, hold time is 180, keepalive interval
is 60 seconds
Neighbor capabilities:
Route refresh: advertised and received(old & new)
Address family ×××v4 Unicast: advertised and received
當BGP鄰居創建好以後,此時R2已經可以學習到×××V4路由,以下:
R2#show ip route vrf vrf1
Routing Table: vrf1
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
80.0.0.0/24 is subnetted, 2 subnets
B 80.4.5.0 [200/0] via 202.1.1.4, 00:57:58
C 80.1.2.0 is directly connected, Ethernet4/0
202.1.1.0/32 is subnetted, 2 subnets
B 202.1.1.1 [20/0] via 80.1.2.1, 00:59:13
B 202.1.1.5 [200/0] via 202.1.1.4, 00:57:58
R1和R5上也有各自的路由信息了,可是此時若是在R1上ping R5,卻不能通,爲何?由於BGP只是用於信令層面上的路由信息的發佈,要打通轉發層面,必須在R2-R3-R4之間配置LDP。
公網標籤和私網標籤
在徹底作好配置以後,咱們能夠在R2和R4上看到公網標籤和私網標籤,公網標籤是由LDP觸發的,因爲指導×××數據報文在MPLS域中轉發,而私網標籤則是由MBGP觸發的,用於指導×××數據在私網×××中的轉發,這一點在跨域的三層×××中體現的比較明顯。從公網和私網標籤的簡單分析,咱們能夠看出×××中的數據轉發時,是攜帶了兩層MPLS標籤的,即內層標籤爲私網標籤,外層標籤爲公網標籤,這裏咱們能夠經過顯示標籤信息和捕獲數據報文映射對比一下。
在R4上顯示LDP公網標籤,能夠看出R4到R2出標籤爲16:
R4#show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 80.2.3.0/24 0 Et4/2 80.3.4.1
17 16 202.1.1.2/32 0 Et4/2 80.3.4.1
18 Pop tag 202.1.1.3/32 0 Et4/2 80.3.4.1
19 Untagged 202.1.1.5/32[V] 3420 Et4/3 80.4.5.2
20 Aggregate 80.4.5.0/24[V] 0
R4#
在R4上顯示MBGP私網標籤,能夠看出到R1的出標籤爲19:
R4#show bgp ***v4 unicast all labels
NetworkNext Hop In label/Out label
Route Distinguisher: 100:1 (vrf1)
80.1.2.0/24 202.1.1.2 nolabel/18
80.4.5.0/24 80.4.5.2 20/aggregate(vrf1)
202.1.1.1/32 202.1.1.2 nolabel/19
202.1.1.5/32 80.4.5.2 19/nolabel
那麼正常的從R5到R1的×××數據的標籤頭就應該是
16|19,從下面捕獲的報文中咱們就能夠看出確實如此:
總結:本文寫的不是很詳細,惟有配置最完整,用以提供給有必定基礎的兄弟參考,網絡這個東西不能閉門造車,溝通越多提升越快。