EVPN Summary

24 11 月, 2020,由 frank撰写

EVPN

在L2VPN中，我们常见的是VPLS，EoMPLS，AoTM等，这些技术主要利用伪线技术（Kompella/Martini）构造虚拟专网或专线，并由MPLS承载。虽然已经可以通过BGP自动发现并创建伪线，但基于伪线技术的L2VPN有很多缺陷，所以需要一个技术可以通过BGP来替代原来的伪线技术，因此才有了EVPN，EVPN带来最大的不同就是通过BGP控制平面来进行MAC学习，而不是数据平面。2015年提出的PBB-EVPN也是属于EVPN的一种。

EVPN带着替换伪线技术的使命而来，同之前一样，主要涉及点到点、点到多点，下图包含了我们常见的几种EVPN（我暂时没有把ETREE列出来），此篇文章主要以几类Route Type为例，展开整理EVPN的内容，以备以后复习

EVPN基础知识

EVPN Instance（ EVI）

即在PE上EVPN路由和转发的实例，每个实例都会共享同一个MAC-VRF。同一个EVI也可以跨多台PE，同一个物理口（bundle）可以属于多个EVI，如下图所示：

Ethernet Segment Identifier（ESI）

ES表示连接到一个或多个PE的“site”，ESI是标识ES的，由10byte组成。ES主要有两种：SHD（single home device）；MHD（Multi-hom device）；在SHD的场景中，ESI是全“0”的，只有在MHD的场景中，ESI是非“0”的

在MHD的常规部署模型里，CE与PE主要通过Bundle LACP连接，两台PE不在需要复杂的老的技术，如M-LACP，而是依靠EVPN来实现互通；根据服务类型和客户的需求，有不同的负载均衡模式，如下所示：

EVPN RD

如上所述，在PE上，EVPN通过BGP来完成MAC地址的学习，这些MAC地址会使用VPN的RD和RT技术来传递，对于RD，有几点需要说明下：

首先在EVPN中，RD “:0” 表示 EVPN全局属性，也可以叫per-Node/ESI RD，这包括RT4和RT1 per-ESI；主要用于DF选举，和 MAC 撤销
其次初始的RT4和RT1 per-ESI会通过RD “:1”发送给其他PE，所以你会在远端PE上发现这个RD的EVPN路由信息，不过注意的是，由于RFC没有定义一个update中包含多少个RTs，因此根据场景，可能会发现RD “:2” 或 “:3”；
最后关于在RD “:0” 和RD “:EVI”中都包含RT1，这有什么区别呢？其实“:0”中存的是RT1 per-ESI，而“:EVI”中存的是RT1 per-EVI；

我们来看下输出结果：

RP/0/RSP0/CPU0:PE1#sh bgp l2vpn evpn  | i Route Distinguisher                                                      
Sat Nov 21 02:03:01.575 UTC
Route Distinguisher: 192.168.0.1:0 (default for vrf ES:GLOBAL)  # PE1's global
Route Distinguisher: 192.168.0.1:300 (default for vrf 300) # PE1's EVI300
Route Distinguisher: 192.168.0.2:0    # PE2's global
Route Distinguisher: 192.168.0.2:1    # sent from PE2
Route Distinguisher: 192.168.0.2:300  # PE2's EVI300
Route Distinguisher: 192.168.0.3:1
Route Distinguisher: 192.168.0.3:300


RP/0/RSP0/CPU0:PE2#sh  bgp l2vpn evpn | i Route Distinguisher:                                                     
Sat Nov 21 02:05:03.617 UTC
Route Distinguisher: 192.168.0.1:0    # PE1's global
Route Distinguisher: 192.168.0.1:1    # sent from PE1
Route Distinguisher: 192.168.0.1:300  # PE1's EVI300
Route Distinguisher: 192.168.0.2:0 (default for vrf ES:GLOBAL)  # PE2's global
Route Distinguisher: 192.168.0.2:300 (default for vrf 300)      # PE2's EVI300
Route Distinguisher: 192.168.0.3:1
Route Distinguisher: 192.168.0.3:300

EVPN Route Type

在EVPN中，控制平面是通过BGP Route Type来承载并传递不同信息的，在这一系列总结中，我会主要围绕Route Type来展示控制平面和数据平面，这样会比较容易揭开EVPN的面纱。另外目前EVPN 的Type已经扩展到10+了，在这里暂时主要讲解最常用的前5种，其他的以后再做补充

EVPN 流量 over SRTE

基于SR MPLS

EVPN ELAN over SRTE
EVPN ELINE over SRTE

基于SRv6

EVPN ELAN over SRTE
EVPN ELINE over SRTE

初始配置及Topology

Topology

PE1 初始配置

interface Bundle-Ether100
 lacp system mac 0100.0100.0100
 load-interval 30
!
interface Bundle-Ether100.33 l2transport
 encapsulation dot1q 33
 rewrite ingress tag pop 1 symmetric
!
interface Loopback0
 ipv4 address 192.168.0.1 255.255.255.255
!
interface HundredGigE0/0/0/1
 bundle id 100 mode active
!
interface HundredGigE0/0/0/2
 ipv4 address 13.1.1.1 255.255.255.0
!
router isis frank
 net 49.1921.6800.0001.00
 address-family ipv4 unicast
  metric-style wide
  segment-routing mpls
 !
 interface Loopback0
  passive
  circuit-type level-2-only
  address-family ipv4 unicast
   prefix-sid absolute 16001
  !
 !
 interface HundredGigE0/0/0/2
  circuit-type level-2-only
  point-to-point
  address-family ipv4 unicast
   fast-reroute per-prefix
   fast-reroute per-prefix ti-lfa
   metric 1
  !
 !
!
router bgp 65001
 bgp router-id 192.168.0.1
 address-family ipv4 unicast
 !
 address-family l2vpn evpn
 !
 neighbor 192.168.0.5
  remote-as 65001
  update-source Loopback0
  address-family l2vpn evpn
  !
 !
!
evpn
 evi 300
  bgp
   route-target import 65001:300
   route-target export 65001:300
  !
  advertise-mac
  !
 !
 interface Bundle-Ether100
  ethernet-segment
   identifier type 0 11.11.11.11.11.11.11.11.11
   bgp route-target 1111.1111.1111
  !
 !
!
l2vpn
 bridge group 100
  bridge-domain 300
   description elan
   interface Bundle-Ether100.33
    split-horizon group
   !
   evi 300
   !
  !

PE2 初始配置

interface Bundle-Ether100
 lacp system mac 0100.0100.0100
 load-interval 30
!
interface Bundle-Ether100.33 l2transport
 encapsulation dot1q 33
 rewrite ingress tag pop 1 symmetric
!
interface Loopback0
 ipv4 address 192.168.0.2 255.255.255.255
!
interface HundredGigE0/0/0/2
 bundle id 100 mode active
!
interface HundredGigE0/0/0/3
 ipv4 address 23.1.1.2 255.255.255.0
!
router isis frank
 net 49.1921.6800.0002.00
 address-family ipv4 unicast
  metric-style wide
  segment-routing mpls
 !
 interface Loopback0
  passive
  circuit-type level-2-only
  address-family ipv4 unicast
   prefix-sid absolute 16002
  !
 !
 interface HundredGigE0/0/0/3
  circuit-type level-2-only
  point-to-point
  address-family ipv4 unicast
   fast-reroute per-prefix
   fast-reroute per-prefix ti-lfa
   metric 1
  !
 !
!
router bgp 65001
 bgp router-id 192.168.0.2
 address-family l2vpn evpn
 !
 neighbor 192.168.0.5
  remote-as 65001
  update-source Loopback0
  address-family l2vpn evpn
  !
 !
!
evpn
 evi 300
  bgp
   route-target import 65001:300
   route-target export 65001:300
  !
  advertise-mac
  !
 !
 interface Bundle-Ether100
  ethernet-segment
   identifier type 0 11.11.11.11.11.11.11.11.11
   bgp route-target 1111.1111.1111
  !
 !
!
l2vpn
 bridge group 100
  bridge-domain 300
   description elan
   interface Bundle-Ether100.33
    split-horizon group
   !
   evi 300
   !
  !

PE3 初始配置

interface Bundle-Ether100
 lacp system mac 0100.0100.0100
 load-interval 30
!
interface Bundle-Ether100.33 l2transport
 encapsulation dot1q 33
 rewrite ingress tag pop 1 symmetric
!
interface Loopback0
 ipv4 address 192.168.0.3 255.255.255.255
!
interface HundredGigE0/0/0/1
 bundle id 100 mode active
!
interface HundredGigE0/0/0/2
 ipv4 address 13.1.1.3 255.255.255.0
!
interface HundredGigE0/0/0/3
 ipv4 address 23.1.1.3 255.255.255.0
!
interface HundredGigE0/0/0/4
 ipv4 address 35.1.1.3 255.255.255.0
!
router isis frank
 net 49.1921.6800.0003.00
 address-family ipv4 unicast
  metric-style wide
  segment-routing mpls
 !
 interface Loopback0
  passive
  circuit-type level-2-only
  address-family ipv4 unicast
   prefix-sid absolute 16003
  !
 !
 interface HundredGigE0/0/0/2
  circuit-type level-2-only
  point-to-point
  address-family ipv4 unicast
   fast-reroute per-prefix
   fast-reroute per-prefix ti-lfa
   metric 1
  !
 !
 interface HundredGigE0/0/0/3
  circuit-type level-2-only
  point-to-point
  address-family ipv4 unicast
   fast-reroute per-prefix
   fast-reroute per-prefix ti-lfa
   metric 1
  !
 !
 interface HundredGigE0/0/0/4
  circuit-type level-2-only
  point-to-point
  address-family ipv4 unicast
   metric 5000
  !
 !
!
router bgp 65001
 bgp router-id 192.168.0.3
 address-family l2vpn evpn
 !
 neighbor 192.168.0.5
  remote-as 65001
  update-source Loopback0
  !
  address-family l2vpn evpn
  !
 !
evpn
 evi 300
  bgp
   route-target import 65001:300
   route-target export 65001:300
  !
  advertise-mac
  !
 !
 interface Bundle-Ether100
  ethernet-segment
   identifier type 0 22.22.22.22.22.22.22.22.22
   bgp route-target 2222.2222.2222
  !
 !
!
l2vpn
 bridge group 100
  bridge-domain 300
   description elan
   interface Bundle-Ether100.33
    split-horizon group
   !
   evi 300
   !
  !

EVPN基本信息

PE1 LFIB

RP/0/RSP0/CPU0:PE1#sh mpls for
Sat Dec  5 07:54:43.861 UTC
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------
16002  16002       SR Pfx (idx 2)     Hu0/0/0/2    13.1.1.3        0           
16003  Pop         SR Pfx (idx 3)     Hu0/0/0/2    13.1.1.3        0           
24000  Pop         EVPN:300 U         BD=0 E       point2point     0           
24001  Pop         EVPN:300 M         BD=0 EIM     point2point     0           
24003  24002       EVPN:300                        192.168.0.2     0           
24004  Pop         SR Adj (idx 1)     Hu0/0/0/2    13.1.1.3        0           
24005  Pop         SR Adj (idx 3)     Hu0/0/0/2    13.1.1.3        0

PE2 LFIB

RP/0/RSP0/CPU0:PE2#sh mpls for
Sat Dec  5 13:07:20.806 UTC
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------
16001  16001       SR Pfx (idx 1)     Hu0/0/0/3    23.1.1.3        0           
16003  Pop         SR Pfx (idx 3)     Hu0/0/0/3    23.1.1.3        162         
24000  Pop         SR Adj (idx 1)     Hu0/0/0/3    23.1.1.3        0           
24001  Pop         SR Adj (idx 3)     Hu0/0/0/3    23.1.1.3        0           
24002  Pop         EVPN:300 U         BD=0 E       point2point     170         
24003  Pop         EVPN:300 M         BD=0 EIM     point2point     640         
24005  24000       EVPN:300                        192.168.0.1     0           
24006  24004       EVPN:300                        192.168.0.3     0

PE3 LFIB

RP/0/RSP0/CPU0:PE3#sh mpls for
Sat Dec  5 12:56:26.731 UTC
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes       
Label  Label       or ID              Interface                    Switched    
------ ----------- ------------------ ------------ --------------- ------------
16001  Pop         SR Pfx (idx 1)     Hu0/0/0/2    13.1.1.1        56          
16002  Pop         SR Pfx (idx 2)     Hu0/0/0/3    23.1.1.2        830         
24000  Pop         SR Adj (idx 1)     Hu0/0/0/3    23.1.1.2        0           
24001  Pop         SR Adj (idx 3)     Hu0/0/0/3    23.1.1.2        0           
24002  Pop         SR Adj (idx 1)     Hu0/0/0/2    13.1.1.1        0           
24003  Pop         SR Adj (idx 3)     Hu0/0/0/2    13.1.1.1        0           
24004  Pop         EVPN:300 U         BD=0 E       point2point     170         
24005  Pop         EVPN:300 M         BD=0 EIM     point2point     320         
24007  Pop         SR Adj (idx 1)     Hu0/0/0/4    35.1.1.5        0           
24008  Pop         SR Adj (idx 3)     Hu0/0/0/4    35.1.1.5        0           
24009  24000       EVPN:300                        192.168.0.1     0           
       24002       EVPN:300                        192.168.0.2     0

config_include_rr_tgn.zip 下载

本文出自 Frank's Blog

本文链接：EVPN Summary
版权声明：本文为原创文章，仅代表个人观点，版权归 Frank Zhao 所有，转载时请注明本文出处及文章链接

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