一、说明

本篇主要描述BGP EVPN VxLAN VNI间(同租户，不同VNI)互通的控制层面操作，同时也描述了BGP EVPN VxLAN相同VNI内主机互通的过程；
本篇也描述了数据层面的转发过程；
本篇网络拓扑和配置信息全部基于前两篇“4 基于BGP EVPN实现Cisco VxLAN实验 & 分布式任播网关”和“5 基于BGP EVPN实现Cisco VxLAN控制层面之MAC学习”；
本篇新加了ARP抑制配置，另外与之前不同，本篇VRF名称由"Tenant-A"变更为"ta"。

二、拓扑

image.png

三、控制层面操作

3.1 MAC-IP学习过程

本节详细介绍了本端VTEP交换机如何从终端主机生成的免费ARP消息中了解其本地连接的主机的IP地址，以及Host Mobility Manager(HMM-主机移动管理器)组件如何将信息装载进相关VNI的L2RIB中(保留MAC-IP地址信息的L2RIB数据库也被称为IP VRF)；
本节展示了如何使用BGP EVPN Route Type 2(MAC/MAC-IP通告路由)将路由从L2RIB导出到BGP Loc-RIB，再通过BGP Adj-RIB-Out通告给远端VTEP交换机；
本节展示了路由信息如何最终到达远端VTEP的L2RIB中。

3.1.1 本端VTEP的ARP学习

PC1启动后，它会发送Gratuitous ARP(GARP-免费ARP)来验证其IP地址的唯一性，VTEP交换机Leaf-1从接口E1/3接收到GARP消息，并将来自PC1 MAC的MAC-IP地址绑定信息和来自GARP有效载荷的PC1 IP字段装载进ARP表中；
下方展示了VRF ta的ARP表。在NX-OS中，本地学习的ARP条目的默认老化时间为1500秒，比MAC地址老化计时器短300秒。当ARP老化计时器超时后，交换机会通过向主机发送ARP请求来检查主机的存在。如果主机响应ARP请求，则交换机将重置老化计时器。如果主机未响应ARP请求，则该条目将从ARP表中删除，但在发送删除消息之前，会在BGP EVPN表中额外保留1800秒(MAC老化计时器)。MAC地址老化定时器应大于ARP老化定时器，这是因为ARP刷新进程还将更新MAC表，并且可以避免不必要的泛洪。

Leaf-1# sh ip arp vrf ta

Flags: * - Adjacencies learnt on non-active FHRP router
       + - Adjacencies synced via CFSoE
       # - Adjacencies Throttled for Glean
       CP - Added via L2RIB, Control plane Adjacencies
       PS - Added via L2RIB, Peer Sync
       RO - Re-Originated Peer Sync Entry
       D - Static Adjacencies attached to down interface

IP ARP Table for context ta
Total number of entries: 1
Address         Age       MAC Address     Interface       Flags
172.16.1.1      00:02:00  0050.7966.6806  Vlan10

3.1.2 本端VTEP的MAC-IP

主机移动管理器组件(HMM)将MAC-IP信息作为本地路由进行学习;
HMM将信息装载进本地主机数据库中，并将MAC-IP信息转发到L2RIB;
本地主机数据库包含有关IP地址(/32)、MAC地址、SVI和本地接口的信息。L2RIB中具有相同的信息(除了没有SVI外)；
下方展示了Leaf-1上部分MAC-IP的学习过程；

Leaf-1# show system internal l2rib event-history mac-ip
L2RIB MAC-IP Object Event Logs:
[10/12/20 14:25:31.870 CST 1 29704] Rcvd MAC-IP ROUTE BASE msg: obj_type: 13 oper_type: 1 oper_sbtype: 0 producer: 12
[10/12/20 14:25:31.870 CST 2 29704] Rcvd MAC-IP ROUTE msg: (10, 0050.7966.6806, 172.16.1.1), l2 vni 0, l3 vni 13960, 
[10/12/20 14:25:31.870 CST 3 29704] Rcvd MAC-IP ROUTE msg: flags , admin_dist 7, seq 0, soo 0, peerid 0, 
[10/12/20 14:25:31.870 CST 4 29704] Rcvd MAC-IP ROUTE msg: res 0, esi (F), ifindex 0, nh_count 0, pc-ifindex 0
[10/12/20 14:25:31.871 CST 5 29704] (10,0050.7966.6806,172.16.1.1):MAC-IP entry created
[10/12/20 14:25:31.871 CST 6 29704] (10,0050.7966.6806,172.16.1.1,12):MAC-IP route created with flags 0, l3 vni 13960, seq 0
[10/12/20 14:25:31.871 CST 7 29704] (10,0050.7966.6806,172.16.1.1,12): admin dist 7, soo 0, peerid 0, peer ifindex 0
[10/12/20 14:25:31.871 CST 8 29704] (10,0050.7966.6806,172.16.1.1,12): esi (F), pc-ifindex 0
[10/12/20 14:25:31.875 CST 9 29704] (10,0050.7966.6806,172.16.1.1,12):Encoding MAC-IP best route (ADD, client id 5), esi: (F)

下方展示了Leaf-上VRF ta的本地主机数据库中与PC1的MAC-IP相关绑定信息；

Leaf-1# show fabric forwarding ip local-host-db vrf ta
HMM host IPv4 routing table information for VRF ta
Status: *-valid, x-deleted, D-Duplicate, DF-Duplicate and frozen, 
        c-cleaned in 00:01:49

    Host                 MAC Address        SVI        Flags      Physical Interface
*   172.16.1.1/32        0050.7966.6806     Vlan10     0x420201   Ethernet1/3

下方表明了有关L2RIB下IP VRF中PC1的MAC-IP的信息是由HMM组件产生的

Leaf-1# show l2route mac-ip topology 10 detail
Flags -(Rmac):Router MAC (Stt):Static (L):Local (R):Remote (V):vPC link 
(Dup):Duplicate (Spl):Split (Rcv):Recv(D):Del Pending (S):Stale (C):Clear
(Ps):Peer Sync (Ro):Re-Originated 
Topology    Mac Address    Prod   Flags         Seq No     Host IP         Next-Hops      
----------- -------------- ------ ---------- --------------- ---------------
10          0050.7966.6806 HMM    --            0          172.16.1.1     Local          
            Sent To: BGP
            L3-Info: 13960

3.1.3 本端VTEP的BGP路由导出

VTEP交换机Leaf-1将来自L2RIB的MAC-IP路由装载进BGP Loc-RIB中；
MAC-IP信息被作为单独的BGP EVPN Route Type 2更新进行通告(使用MAC-only和MAC IP的专用NLRI更新)，MAC-only和MAC-IP路由更新携带的NLRI信息的区别在于：MAC-IP通告除了携带主机的MAC地址外，还携带了主机的IP地址、掩码信息以及MPLS标签栈2的信息，该信息定义了VRF ta中使用的L3VNI；
另外MAC-IP更新消息中还有两个扩展团体属性，包含RT 65234:13960和路由器MAC 5e00.0000.0007；
下方展示了VTEP交换机Leaf-1如何接收MAC-IP路由信息并将其安装到RIB和BGP Loc-RIB中的内部过程，掩码长度包括RD(8×8bit)+MAC地址(6×8bit)+IP地址(4×8bit)=18个8bit即144bit；

Leaf-1# show bgp internal event-history events | in 6806
BRIB：
2020 Oct 12 17:36:36.317231: (default) BRIB: [L2VPN EVPN] Installing prefix 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/144 (local) via 3.3.3.3 label 10010 (0x0/0x0) into BRIB with extcomm Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007
RIB：
2020 Oct 12 17:36:36.319783: (default) RIB: [L2VPN EVPN] add prefix 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1] (flags 0x1) : OK
, total 1
EVENT：
2020 Oct 12 17:36:36.316899: EVT: Received from L2RIB MAC-IP route: Add ESI 0000.0000.0000.0000.0000 topo 10010 mac 0050.7966.6806 ip 172.16.1.1 L3 VN
I 13960 flags 00000000 soo 0 seq 0, reorig :0

下方展示有关PC1的MAC-IP NLRI的BGP Loc-RIB；

Leaf-1# sh bgp l2vpn evpn 172.16.1.1
BGP routing table information for VRF default, address family L2VPN EVPN
Route Distinguisher: 3.3.3.3:32777    (L2VNI 10010)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272, version 969
Paths: (1 available, best #1)
Flags: (0x000102) (high32 00000000) on xmit-list, is not in l2rib/evpn

  Advertised path-id 1
  Path type: local, path is valid, is best path
  AS-Path: NONE, path locally originated
    3.3.3.3 (metric 0) from 0.0.0.0 (3.3.3.3)
      Origin IGP, MED not set, localpref 100, weight 32768
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007

  Path-id 1 advertised to peers:
    1.1.1.1            2.2.2.2

上方输出中的前缀信息解释可参考下表；

前缀信息	说明	备注
2	BGP EVPN Route-Type 2	MAC/MAC-IP路由通告
0	Ethernet Segment Identifier (ESI)	全部置零=单宿主站点
0	Ethernet Tag Id	EVPN路由必须使用0
48	MAC地址长度	/
0050.7966.6806	MAC地址	/
32	IP地址长度	/
172.16.1.1	IP地址	/
/272	MAC-IP VRF NLRI的长度(以bit为单位)	RD(8×8bit) + MAC address(6×8bit) + L2VNI Id(3×8bit) + L3VNI Id(3×8bit) + IP address(4×8bit) + ESI(10×8bit) = 34×8bit即272bits

上方输出中的L2VNI信息显示在“Received label”字段中，另外还有三个BGP扩展团体属性；

BGP扩展团体	说明	备注
RT:65234:10010	用于导出/导入策略(L2VNI)	VNI 10010对应VLAN 10
RT:65234:13960	用于导出/导入策略(L3VNI)	VNI 13960对应VLAN 3960
ENCAP:8	定义数据层面的封装类型为VxLAN	/
Router MAC:5000.0003.0007	用于路由数据包的内层MAC头源地址	这是必要的，因为VxLAN为MAC in UDP封装机制，并且L3边界上的数据有效负载不携带源主机的MAC地址，所以使用RMAC。

3.1.4 远端VTEP的BGP路由导入

VTEP交换机Leaf-2接收BGP EVPN MAC路由通告并将其装载进BGP Adj-RIB-In数据库中，并且无需进行任何修改；
Leaf-2从BGP Adj-RIB-In数据库中将路由导入到BGP Loc-RIB，并通过最佳路径选择进程将其装载进L2RIB；
当远端VTEP交换机Leaf-2将路由从BGP Adj-RIB装载进BGP Loc-RIB时，它将根据其BGP RID:VLAN ID组合将RD更改为4.4.4.4:32777，此过程与MAC-only路由导入相同，并且基于相同的RT 65234:10010；
下方展示了内部导入过程，Leaf-2将接收到的MAC-IP路由装载进RD 3.3.3.3:32777的BGP Adj-RIB-In中，再将此路由导入到RD 4.4.4.4:32777的BGP Adj-RIB-In中，并装载进BGP Loc-RIB中，最后将其导入L2RIB中。请注意，下方输出还包含L3RIB的装载过程；

Leaf-2# show bgp internal event-history events | i 6806
2020 Oct 12 21:52:48.495013: (default) RIB: [L2VPN EVPN]: Send to L2RIB 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:
[0]:[0.0.0.0]/112
2020 Oct 12 21:52:48.494399: (default) RIB: [L2VPN EVPN] For 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0.0.
0]/112, added 0 next hops, suppress 0
2020 Oct 12 21:52:48.494371: (default) RIB: [L2VPN EVPN] Add/delete 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:
[0.0.0.0]/112, flags=0x210, in_rib: yes
2020 Oct 12 21:52:48.493006: (default) BRIB: [L2VPN EVPN] Marking imported path for dest 4.4.4.4:32777:[2]:[0]:[0]:[48]:
[0050.7966.6806]:[0]:[0.0.0.0]/112 as deleted, path ibgp
2020 Oct 12 21:52:48.492893: EVT: [L2VPN EVPN] Deleting imported path [2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0.0.0]
2020 Oct 12 21:52:48.492506: (default) RIB: [L2VPN EVPN] Add/delete 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:
[0.0.0.0]/112, flags=0x200, evi_ctx invalid, in_rib: no
2020 Oct 12 21:52:48.491786: (default) BRIB: [L2VPN EVPN] Marking path for dest 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.796
6.6806]:[0]:[0.0.0.0]/112 from peer 2.2.2.2 as deleted, pflags = 0x40000011, reeval=0
2020 Oct 12 21:52:48.474282: (default) RIB: [L2VPN EVPN] Suppressing 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]
:[0.0.0.0]/112 download to L2RIB
2020 Oct 12 21:52:48.474255: (default) RIB: [L2VPN EVPN] For 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0.0.
0]/112, added 1 next hops, suppress 1
2020 Oct 12 21:52:48.474189: (default) RIB: [L2VPN EVPN] Adding 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0
.0.0]/112 via 3.3.3.3 to NH list (flags2: 0x0)
2020 Oct 12 21:52:48.473909: (default) RIB: [L2VPN EVPN] Add/delete 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:
[0.0.0.0]/112, flags=0x210, in_rib: yes
2020 Oct 12 21:52:48.473593: (default) IMP: [L2VPN EVPN] Import of 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[
0.0.0.0]/112 (EVI: 0) to RD 4.4.4.4:65534 (0) inhibited, no Type2 for EAD-ES import
2020 Oct 12 21:52:48.472917: (default) IMP: [L2VPN EVPN] Importing prefix 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806
]:[0]:[0.0.0.0]/112 to  RD 4.4.4.4:32777
2020 Oct 12 21:52:48.466435: (default) RIB: [L2VPN EVPN] Add/delete 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:
[0.0.0.0]/112, flags=0x200, evi_ctx invalid, in_rib: no
2020 Oct 12 21:52:48.465106: (default) BRIB: [L2VPN EVPN] Marking path for dest 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.796
6.6806]:[0]:[0.0.0.0]/112 from peer 1.1.1.1 as deleted, pflags = 0x40000011, reeval=0
2020 Oct 12 21:47:48.453800: (default) RIB: [L2VPN EVPN]: Send to L2RIB 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:
[0]:[0.0.0.0]/112
2020 Oct 12 21:47:48.451605: (default) RIB: [L2VPN EVPN] For 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0.0.
0]/112, added 1 next hops, suppress 0
2020 Oct 12 21:47:48.451584: (default) RIB: [L2VPN EVPN] Adding 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:[0.0
.0.0]/112 via 3.3.3.3 to NH list (flags2: 0x0)
2020 Oct 12 21:47:48.451553: (default) RIB: [L2VPN EVPN] Add/delete 4.4.4.4:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[0]:
[0.0.0.0]/112, flags=0x200, in_rib: no

下方展示了Leaf-2上BGP-RIB(BRIB)的部分输出(Adj-RIB-In和Loc-RIB)。输出的上半部分描述了从Spine-1接收到的原始、未修改的NLRI，该NLRI装载在Adj-RIB-In中。输出的中间部分显示了已装载进BGP Loc-RIB中并且修改了RD值的相同NLRI，此NLRI基于RT 65234:10010实现路由的正确导入。输出的下半部分显示了与中间部分相同的NLRI(此NLRI与RD 4.4.4.4:3一同装载)，它用于VNI间(L3VNI)的流量转发，基于在VRF Context中的配置自动生成的RT 65234:13960导入到相关的L3VNI Loc-RIB。

Leaf-2# show bgp l2vpn evpn 172.16.1.1 vrf ta
BGP routing table information for VRF default, address family L2VPN EVPN
Route Distinguisher: 3.3.3.3:32777
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272, version 801
Paths: (2 available, best #2)
Flags: (0x000202) (high32 00000000) on xmit-list, is not in l2rib/evpn, is not in HW

  Path type: internal, path is valid, not best reason: Neighbor Address
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 2.2.2.2 (2.2.2.2)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007
      Originator: 3.3.3.3 Cluster list: 2.2.2.2 

  Advertised path-id 1
  Path type: internal, path is valid, is best path
             Imported to 3 destination(s)
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

Route Distinguisher: 4.4.4.4:32777    (L2VNI 10010)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272, version 824
Paths: (1 available, best #1)
Flags: (0x000212) (high32 00000000) on xmit-list, is in l2rib/evpn, is not in HW

  Advertised path-id 1
  Path type: internal, path is valid, is best path, in rib
             Imported from 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272 
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

Route Distinguisher: 4.4.4.4:3    (L3VNI 13960)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272, version 799
Paths: (1 available, best #1)
Flags: (0x000202) (high32 00000000) on xmit-list, is not in l2rib/evpn, is not in HW

  Advertised path-id 1
  Path type: internal, path is valid, is best path
             Imported from 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/272 
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

3.1.5 远端VTEP的IP VRF

远端VTEP Leaf-2会验证从NLRI找到的下一跳IP地址的可达性，HMM组件将MAC-IP路由装载进L2RIB中。这时本地拓扑ID为10(基于VLAN 10)，路由信息的来源是BGP，下一跳接口信息指向VTEP交换机Leaf-1的NVE1接口绑定的源IP地址；
在此阶段，两个VTEP交换机在其L2RIB以及BGP表中都具有了PC1的MAC-IP信息，但是只有本端VTEP交换机Leaf-1才将MAC-IP绑定信息装载进ARP表中；
下方展示了Leaf-2上的部分MAC-IP学习过程；

Leaf-2# sh system internal l2rib event-history mac-ip
L2RIB MAC-IP Object Event Logs:
[10/12/20 14:25:33.711 CST 1 29679] Rcvd MAC-IP ROUTE BASE msg: obj_type: 13 oper_type: 1 oper_sbtype: 0 producer: 5
[10/12/20 14:25:33.711 CST 2 29679] Rcvd MAC-IP ROUTE msg: (10, 0050.7966.6806, 172.16.1.1), l2 vni 0, l3 vni 0, 
[10/12/20 14:25:33.711 CST 3 29679] Rcvd MAC-IP ROUTE msg: flags , admin_dist 0, seq 0, soo 0, peerid 0, 
[10/12/20 14:25:33.711 CST 4 29679] Rcvd MAC-IP ROUTE msg: res 0, esi (F), ifindex 0, nh_count 1, pc-ifindex 0
[10/12/20 14:25:33.711 CST 5 29679] NH: 3.3.3.3
[10/12/20 14:25:33.713 CST 6 29679] (10,0050.7966.6806,172.16.1.1):MAC-IP entry created
[10/12/20 14:25:33.713 CST 7 29679] (10,0050.7966.6806,172.16.1.1,5):MAC-IP route created with flags 0, l3 vni 0, seq 0
[10/12/20 14:25:33.713 CST 8 29679] (10,0050.7966.6806,172.16.1.1,5): admin dist 20, soo 0, peerid 0, peer ifindex 0
[10/12/20 14:25:33.714 CST 9 29679] (10,0050.7966.6806,172.16.1.1,5): esi (F), pc-ifindex 0
[10/12/20 14:25:45.795 CST a 29679] Rcvd MAC-IP ROUTE BASE msg: obj_type: 13 oper_type: 1 oper_sbtype: 0 producer: 12
[10/12/20 14:25:45.795 CST b 29679] Rcvd MAC-IP ROUTE msg: (10, 0050.7966.6808, 172.16.1.3), l2 vni 0, l3 vni 13960, 
[10/12/20 14:25:45.795 CST c 29679] Rcvd MAC-IP ROUTE msg: flags , admin_dist 7, seq 0, soo 0, peerid 0, 
[10/12/20 14:25:45.795 CST d 29679] Rcvd MAC-IP ROUTE msg: res 0, esi (F), ifindex 0, nh_count 0, pc-ifindex 0
[10/12/20 14:25:45.795 CST e 29679] (10,0050.7966.6808,172.16.1.3):MAC-IP entry created
[10/12/20 14:25:45.795 CST f 29679] (10,0050.7966.6808,172.16.1.3,12):MAC-IP route created with flags 0, l3 vni 13960, s
eq 0
[10/12/20 14:25:45.795 CST 10 29679] (10,0050.7966.6808,172.16.1.3,12): admin dist 7, soo 0, peerid 0, peer ifindex 0
[10/12/20 14:25:45.795 CST 11 29679] (10,0050.7966.6808,172.16.1.3,12): esi (F), pc-ifindex 0
[10/12/20 14:25:45.800 CST 12 29679] (10,0050.7966.6808,172.16.1.3,12):Encoding MAC-IP best route (ADD, client id 5), es

下方表明了L2RIB中的MAC-IP信息是由BGP产生的；

Leaf-2# show l2route mac-ip topology 10 detail
Flags -(Rmac):Router MAC (Stt):Static (L):Local (R):Remote (V):vPC link 
(Dup):Duplicate (Spl):Split (Rcv):Recv(D):Del Pending (S):Stale (C):Clear
(Ps):Peer Sync (Ro):Re-Originated 
Topology    Mac Address    Prod   Flags         Seq No     Host IP         Next-Hops      
----------- -------------- ------ ---------- --------------- ---------------
10          0050.7966.6806 BGP    --            0          172.16.1.1     3.3.3.3        
            Sent To: ARP

经过以上阶段，两个VTEP交换机都具有了PC1的MAC-IP信息。

3.2 ARP抑制

章节3.1说明了如何在BGP EVPN VxLAN Fabric中传播MAC-IP地址信息。本节介绍了VTEP交换机的ARP抑制机制如何利用MAC-IP绑定信息来减少VxLAN Fabric中不必要的2层BUM(广播、未知单播、组播)流量。

3.2.1 配置Leaf交换机：启用ARP抑制

Leaf-1配置：

interface nve1
  member vni 10010
    suppress-arp
  member vni 10020
    suppress-arp

Leaf-2配置：

interface nve1
  member vni 10010
    suppress-arp
  member vni 10020
    suppress-arp

Leaf-3配置：

interface nve1
  member vni 10010
    suppress-arp
  member vni 10020
    suppress-arp

3.2.2 查看ARP抑制缓存

从启动PC1的阶段开始，当PC1开机后，PC1将GARP/ARP消息发送到网络，Leaf-1将MAC-IP绑定信息安装载进VRF ta的ARP表中，下方展示了Leaf-1的ARP表；

Leaf-1# show  ip arp vrf ta
Flags: * - Adjacencies learnt on non-active FHRP router
       + - Adjacencies synced via CFSoE
       # - Adjacencies Throttled for Glean
       CP - Added via L2RIB, Control plane Adjacencies
       PS - Added via L2RIB, Peer Sync
       RO - Re-Originated Peer Sync Entry
       D - Static Adjacencies attached to down interface

IP ARP Table for context ta
Total number of entries: 1
Address         Age       MAC Address     Interface       Flags
172.16.1.1      00:01:03  0050.7966.6806  Vlan10

当在本端VTEP交换机上启用基于VNI的ARP抑制时，MAC-IP地址绑定信息也会从ARP表装载进本地ARP抑制缓存中，下方展示了Leaf-1的ARP抑制缓存表；

Leaf-1# show ip arp suppression-cache detail
Flags: + - Adjacencies synced via CFSoE
       L - Local Adjacency
       R - Remote Adjacency
       L2 - Learnt over L2 interface
       PS - Added via L2RIB, Peer Sync
       RO - Dervied from L2RIB Peer Sync Entry

Ip Address      Age      Mac Address    Vlan Physical-ifindex    Flags    Remote
 Vtep Addrs

172.16.1.1      00:03:55 0050.7966.6806   10 Ethernet1/3         L

在远端VTEP交换机(Leaf-2)上启用ARP抑制后，ARP抑制缓存信息将从L2RIB中获取。下方展示了Leaf-2上关于PC1的ARP抑制缓存表；

Leaf-2# show ip arp suppression-cache detail
Flags: + - Adjacencies synced via CFSoE
       L - Local Adjacency
       R - Remote Adjacency
       L2 - Learnt over L2 interface
       PS - Added via L2RIB, Peer Sync
       RO - Dervied from L2RIB Peer Sync Entry

Ip Address      Age      Mac Address    Vlan Physical-ifindex    Flags    Remote Vtep Addrs

172.16.1.1      05:01:11 0050.7966.6806   10 (null)              R        3.3.3.3

3.2.3 抑制场景对比：

无抑制：当收到ARP请求报文时，本地所有ARP请求都发往VNI所关联的组播组，并且所有加入该组播组的VTEP交换机都会接收ARP请求消息，并将其转发到数据包VxLAN包头中VNI ID所定义的广播域的端口；
ARP抑制：当收到ARP请求报文时，本地VTEP交换机检查请求的MAC-IP绑定信息是否存储在本地ARP抑制缓存中。如果检查通过，则本地交换机直接将ARP回复发送给请求者，而不会将ARP请求泛洪到网络中。如果ARP抑制缓存检查未命中，则将ARP请求泛洪到网络中(建议在Intra-VNI访问可达性测试之通过后再启用ARP抑制)；
ARP和未知单播抑制：在命中ARP抑制检查的情况下，其工作原理与ARP抑制相同。但是如果未命中，则会丢弃ARP请求，所以此特性要求VxLAN Fabric中不能有静默主机。

3.3 主机路由通告：VNI间路由(L3VNI)

上篇和本篇前半部分介绍了终端主机的MAC和MAC-IP信息如何在VxLAN Fabirc中传播以及如何利用这些信息实现VNI内交换和MAC地址解析，也介绍了利用ARP抑制机制减少BUM流量。本节将说明如何将主机路由导入L3RIB，以及如何利用此信息实现VNI间路由。

3.3.1 本端VTEP RIB中的主机路由

章节3.1介绍了本地VTEP交换机如何将MAC-IP地址绑定信息装载进ARP表中，以及HMM(主机移动管理器)组件如何将信息装载进L2RIB中。除了此过程之外，HMM组件还会将ARP表中的MAC-IP信息装载进L3RIB中；
下方展示了本地VTEP交换机Leaf-1中的VRF ta的RIB。该路由是从VLAN 10中获悉的，并由HMM装载进RIB中；

Leaf-1# show  ip route  172.16.1.1 vrf ta
IP Route Table for VRF "ta"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%' in via output denotes VRF 

172.16.1.1/32, ubest/mbest: 1/0, attached
    *via 172.16.1.1, Vlan10, [190/0], 1d05h, hmm

3.3.2 本端VTEP上BGP进程中的主机路由

章节3.1还介绍了如何将MAC-IP信息从L2RIB发送到Loc-RIB，再从Loc-RIB发送到Adj-RIB-Out，然后将其通告为BGP EVPN Route type 2，发送至到远端VTEP交换机；
下方展示了与PC1的IP地址相关的BGP Loc-RIB；

Leaf-1# show bgp l2vpn evpn 172.16.1.1
BGP routing table information for VRF default, address family L2VPN EVPN
Route Distinguisher: 3.3.3.3:32777    (L2VNI 10010)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/
272, version 969
Paths: (1 available, best #1)
Flags: (0x000102) (high32 00000000) on xmit-list, is not in l2rib/evpn

  Advertised path-id 1
  Path type: local, path is valid, is best path
  AS-Path: NONE, path locally originated
    3.3.3.3 (metric 0) from 0.0.0.0 (3.3.3.3)
      Origin IGP, MED not set, localpref 100, weight 32768
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0
007

  Path-id 1 advertised to peers:
    1.1.1.1            2.2.2.2

3.3.3 远端VTEP上BGP进程中的主机路由

章节3.1没有说明MAC-IP路由信息如何最终进入远端VTEP交换机的L3RIB；
有关PC1 MAC-IP NLRI的BGP EVPN Route Type 2更新还包含了RT 65234:13960(L3VNI)；
接收到的NLRI信息通过BGP的Import Policy Engine(基于RT 65234:13960导入)发送，最终将L3VNI条目发送到Loc-RIB；
在Input Policy处理期间，原始RD 3.3.3.3:32777更改为VRF ta特定的RD 4.4.4.4:3:3(3 = VRF ta的VRF ID)，RD用于在不同的VRF中的区分重叠的IP地址；
下方展示了Leaf-2的BGP表，可以看到上方描述的所有详细信息(其中包含了原始的信息、修改RD后的信息、L3VNI信息等)；

Leaf-2# show bgp l2vpn evpn 172.16.1.1 
BGP routing table information for VRF default, address family L2VPN EVPN
Route Distinguisher: 3.3.3.3:32777
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/
272, version 801
Paths: (2 available, best #2)
Flags: (0x000202) (high32 00000000) on xmit-list, is not in l2rib/evpn, is not i
n HW

  Path type: internal, path is valid, not best reason: Neighbor Address
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 2.2.2.2 (2.2.2.2)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0
007
      Originator: 3.3.3.3 Cluster list: 2.2.2.2 

  Advertised path-id 1
  Path type: internal, path is valid, is best path
             Imported to 3 destination(s)
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0
007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

Route Distinguisher: 4.4.4.4:32777    (L2VNI 10010)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/
272, version 824
Paths: (1 available, best #1)
Flags: (0x000212) (high32 00000000) on xmit-list, is in l2rib/evpn, is not in HW

  Advertised path-id 1
  Path type: internal, path is valid, is best path, in rib
             Imported from 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:
[172.16.1.1]/272 
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0
007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

Route Distinguisher: 4.4.4.4:3    (L3VNI 13960)
BGP routing table entry for [2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:[172.16.1.1]/
272, version 799
Paths: (1 available, best #1)
Flags: (0x000202) (high32 00000000) on xmit-list, is not in l2rib/evpn, is not i
n HW

  Advertised path-id 1
  Path type: internal, path is valid, is best path
             Imported from 3.3.3.3:32777:[2]:[0]:[0]:[48]:[0050.7966.6806]:[32]:
[172.16.1.1]/272 
  AS-Path: NONE, path sourced internal to AS
    3.3.3.3 (metric 81) from 1.1.1.1 (1.1.1.1)
      Origin IGP, MED not set, localpref 100, weight 0
      Received label 10010 13960
      Extcommunity: RT:65234:10010 RT:65234:13960 ENCAP:8 Router MAC:5000.0003.0
007
      Originator: 3.3.3.3 Cluster list: 1.1.1.1 

  Path-id 1 not advertised to any peer

下方展示了Leaf-2上的VRF信息，其中包含了VRF ID；

Leaf-2# show vrf
VRF-Name                           VRF-ID State   Reason                        
default                                 1 Up      --                            
management                              2 Up      --                            
ta                                      3 Up      --

3.3.4 将主机路由装载进远端VTEP的RIB

该路由已从BGP Loc-RIB装载进L3 RIB。RIB条目包括有关下一跳地址和隧道ID、封装类型(VxLAN)、网段ID和路由来源(BGP)信息；
在此阶段，本端VTEP交换机Leaf-1和远端VTEP交换机Leaf-2都能够将来自不同L2VNI主机的流量(VNI间流量)路由到PC1(属于L2VNI 10010)。
下方展示了Leaf-2上VRF ta RIB中有关172.16.1.1/32的路由条目；

Leaf-2# show ip route 172.16.1.1 vrf ta 
IP Route Table for VRF "ta"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%' in via output denotes VRF 

172.16.1.1/32, ubest/mbest: 1/0
    *via 3.3.3.3%default, [200/0], 1d02h, bgp-65234, internal, tag 65234 (evpn) 
segid: 13960 tunnelid: 0x3030303 encap: VXLAN

下方展示了BGP递归数据库，其中3.3.3.3用于目标172.16.1.1的下一跳；

Leaf-2# show nve internal bgp rnh database vni 13960
--------------------------------------------
Total peer-vni msgs recvd from bgp: 23
Peer add requests: 14
Peer update requests: 0
Peer delete requests: 9
Peer add/update requests: 14
Peer add ignored (peer exists): 0
Peer update ignored (invalid opc): 0
Peer delete ignored (invalid opc): 0
Peer add/update ignored (malloc error): 0
Peer add/update ignored (vni not cp): 0
Peer delete ignored (vni not cp): 0
--------------------------------------------
Showing BGP RNH Database, size : 5 vni 13960 

Flag codes: 0 - ISSU Done/ISSU N/A        1 - ADD_ISSU_PENDING         
            2 - DEL_ISSU_PENDING          3 - UPD_ISSU_PENDING
        

VNI    Peer-IP            Peer-MAC            Tunnel-ID  Encap     (A/S)  FlagsP
T   
13960  3.3.3.3            5000.0003.0007      0x3030303  vxlan     (1/0)    0  F
AB
13960  5.5.5.5            5000.0005.0007      0x5050505  vxlan     (1/0)    0  F
AB

下方展示了Leaf-2上关于VRF ta的完整路由表；

Leaf-2# show  ip route vrf ta
IP Route Table for VRF "ta"
'*' denotes best ucast next-hop
'**' denotes best mcast next-hop
'[x/y]' denotes [preference/metric]
'%' in via output denotes VRF 

172.16.1.0/24, ubest/mbest: 1/0, attached
    *via 172.16.1.254, Vlan10, [0/0], 1d06h, direct
172.16.1.1/32, ubest/mbest: 1/0
    *via 3.3.3.3%default, [200/0], 1d02h, bgp-65234, internal, tag 65234 (evpn) 
segid: 13960 tunnelid: 0x3030303 encap: VXLAN
 
172.16.1.3/32, ubest/mbest: 1/0, attached
    *via 172.16.1.3, Vlan10, [190/0], 1d06h, hmm
172.16.1.5/32, ubest/mbest: 1/0
    *via 5.5.5.5%default, [200/0], 1d02h, bgp-65234, internal, tag 65234 (evpn) 
segid: 13960 tunnelid: 0x5050505 encap: VXLAN
 
172.16.1.254/32, ubest/mbest: 1/0, attached
    *via 172.16.1.254, Vlan10, [0/0], 1d06h, local
172.16.2.0/24, ubest/mbest: 1/0, attached
    *via 172.16.2.254, Vlan20, [0/0], 1d06h, direct
172.16.2.2/32, ubest/mbest: 1/0, attached
    *via 172.16.2.2, Vlan20, [190/0], 1d06h, hmm
172.16.2.4/32, ubest/mbest: 1/0
    *via 5.5.5.5%default, [200/0], 1d02h, bgp-65234, internal, tag 65234 (evpn) 
segid: 13960 tunnelid: 0x5050505 encap: VXLAN
 
172.16.2.254/32, ubest/mbest: 1/0, attached
    *via 172.16.2.254, Vlan20, [0/0], 1d06h, local

四、数据层面操作

4.1 ARP抑制过程

当PC1开机后，即使我们在VTEP Leaf-1的NVE1接口下启用了ARP抑制，从主机PC1接收到的GARP也会被VxLAN封装并泛洪到组播组239.0.0.1；
这是因为VTEP Leaf-1在ARP表和ARP抑制缓存中都没有有关主机PC1的IP/MAC地址信息；
从下方VTEP Leaf-1的Debug输出中也可以看到上方关于ARP的描述过程，Leaf-从主机PC1接收GARP，它没有172.16.1.1的缓存条目，因此必须泛洪该帧，然后Leaf-将更新其ARP抑制缓存和L2RIB；

Leaf-1# terminal monitor
Leaf-1# debug ip arp cache
Leaf-1# debug ip arp event
Leaf-1# debug ip arp suppression-event
Leaf-1# 
Leaf-1# 2020 Oct 13 20:47:51.940670 arp: arp_process_receive_packet_msg: VINCI: Anycast Proxy mode  
2020 Oct 13 20:47:51.940988 arp: arp_process_packet_in_l3_mode: GARP:  Vlan: 10, Dest-ip: 172.16.1.1, Mac-Addr: 0050.7966.6806, ifindex: 0x0   
2020 Oct 13 20:47:51.941107 arp: arp_cache_resolve_l3_addr: arp_cache_resolve_l3_addr 
2020 Oct 13 20:47:51.941173 arp: arp_cache_resolve_l3_addr: mac: 0050.7966.6806, phy-ifindex:0x1a000400, is_local:TRUE 
2020 Oct 13 20:47:51.941283 arp: arp_process_receive_packet_msg: GARP count on the interface Vlan10 is 1 
2020 Oct 13 20:47:51.941696 arp: arp_process_receive_packet_msg: NO GARP storm on interface Vlan10 
2020 Oct 13 20:47:51.941771 arp: arp_process_receive_packet_msg: Existing entry found for source 172.16.1.1 on Vlan10 
2020 Oct 13 20:47:51.941839 arp: arp_add_adj: arp_add_adj: Updating MAC on interface Vlan10, phy-interface Ethernet1/3, flags:0x1 
2020 Oct 13 20:47:51.941927 arp: arp_adj_update_state_get_action_on_add: Successful action on add Previous State:0x10, Current State:0x10 Received event:Data Plane Add, entry: 172.16.1.1, 0050.7966.6806, Vlan10, action to be taken send_to_am:FALSE, arp_aging:TRUE 
2020 Oct 13 20:47:51.942079 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Create request for sw-bd: 10, mac: 0050.7966.6806 ip: 172.16.1.1, uuid: 268, vlan_mode: 2, ifindex: 0x901000a, phyifindex 0x1a000400 
2020 Oct 13 20:47:51.942191 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Post L2FM lookup MAC binding : for sw-bd: 10, mac: 0050.7966.6806 ip: 172.16.1.1, uuid: 268, vlan_mode: 2, ifindex: 0x901000a, phyifindex 0x1a000400 
2020 Oct 13 20:47:51.942251 arp: arp_cache_create_cache_node: create node for uuid:268, sw-bd:10, ip:172.16.1.1, mac:0050.7966.6806, mode:2, flags:0x10 is_timer: 0 
2020 Oct 13 20:47:51.942396 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Entry with same ip/vlan exists 
2020 Oct 13 20:47:51.942472 arp: arp_add_adj: Entry added for 172.16.1.1, 0050.7966.6806, state 2 on interface Vlan10, physical interface Ethernet1/3, ismct 0. flags:0x10, Rearp (interval: 0, count: 0), TTL: 1500 seconds update_shm:TRUE 
2020 Oct 13 20:47:51.942541 arp: arp_add_adj: Adj info: iod: 139, phy-iod: 9, ip: 172.16.1.1, mac: 0050.7966.6806, type: 0, sync: FALSE, suppress-mode: L2/L3 ARP Suppression flags:0x10 
2020 Oct 13 20:47:51.942595 arp: arp_process_receive_packet_msg: VINCI: enhanced_proxy: 0, traditional_proxy: 1, adj_added: 0 
2020 Oct 13 20:47:51.943681 arp: arp_cache_create_cache_node: create node for uuid:268, sw-bd:10, ip:172.16.1.1, mac:0050.7966.6806, mode:2, flags:0x10 is_timer: 0 
2020 Oct 13 20:47:51.944623 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Entry with same ip/vlan exists 
2020 Oct 13 20:47:51.944702 arp: arp_add_adj: Entry added for 172.16.1.1, 0050.7966.6806, state 2 on interface Vlan10, physical interface Ethernet1/3, ismct 0. flags:0x10, Rearp (interval: 0, count: 0), TTL: 1500 seconds update_shm:TRUE 
2020 Oct 13 20:47:51.945113 arp: arp_add_adj: Adj info: iod: 139, phy-iod: 9, ip: 172.16.1.1, mac: 0050.7966.6806, type: 0, sync: FALSE, suppress-mode: L2/L3 ARP Suppression flags:0x10 
2020 Oct 13 20:47:51.945239 arp: arp_process_receive_packet_msg: Received ARP request on Vlan10 (Ethernet1/3) 
2020 Oct 13 20:47:51.945375 arp: arp_process_receive_packet_msg: Gratuitous ARP request received on Vlan10 (Ethernet1/3).Proxy or Anycast Gateway enabled on Vlan10.Dropping the packet

下方展示了Leaf-2上的Debug ARP中关于PC1的输出；

Leaf-2# terminal monitor
Leaf-2# debug ip arp cache
Leaf-2# debug ip arp event
Leaf-2# debug ip arp suppression-event
Leaf-2# 
2020 Oct 13 20:55:25.960139 arp: arp_l2rib_msg_cb: arp_l2rib_msg_cb: (Type: Route) Len: 184 Seq: 0, del: 0 (Prod: 5) , peer-id = 0 
2020 Oct 13 20:55:25.960255 arp: arp_l2rib_msg_cb: MAC address: 0050.7966.6806 Remote Host IP: 172.16.1.1 
2020 Oct 13 20:55:25.960564 arp: arp_l2rib_msg_cb: Host IP 172.16.1.1, Remote vtep addr count = 1 
2020 Oct 13 20:55:25.960647 arp: arp_l2rib_msg_cb: RNHs : 3.3.3.3 
2020 Oct 13 20:55:25.960752 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Create request for sw-bd: 10, mac: 0050.7966.6806 ip: 172.16.1.1, uuid: 1290, vlan_mode: 2, ifindex: 0x0, phyifindex 0x0 
2020 Oct 13 20:55:25.960893 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Failed to get phy_iod for ifindex 0x0 : Reason no such pss key 
2020 Oct 13 20:55:25.960964 arp: arp_cache_add_entry_to_cache_and_upd_l2rib: Post L2FM lookup MAC binding : for sw-bd: 10, mac: 0050.7966.6806 ip: 172.16.1.1, uuid: 1290, vlan_mode: 2, ifindex: 0x0, phyifindex 0x0 
2020 Oct 13 20:55:25.961034 arp: arp_cache_create_cache_node: create node for uuid:1290, sw-bd:10, ip:172.16.1.1, mac:0050.7966.6806, mode:2, flags:0x0 is_timer: 0 
2020 Oct 13 20:55:25.961282 arp: arp_cache_create_cache_node: Host IP 172.16.1.1, Remote vtep addr count = 1 
2020 Oct 13 20:55:25.961349 arp: arp_cache_create_cache_node: RNHs : 3.3.3.3 
2020 Oct 13 20:55:25.961622 arp: arp_cache_create_cache_node: New entry: create node 0x6c13ea74 0x6c13ee1c, uuid: 1290, sw-bd: 10, ip:172.16.1.1, mac: 0050.7966.6806, is_local: FALSE, num-macs: 1

下方展示了Leaf-1的ARP缓存抑制表；

Leaf-1# show ip arp suppression-cache detail 
Flags: + - Adjacencies synced via CFSoE
       L - Local Adjacency
       R - Remote Adjacency
       L2 - Learnt over L2 interface
       PS - Added via L2RIB, Peer Sync
       RO - Dervied from L2RIB Peer Sync Entry

Ip Address      Age      Mac Address    Vlan Physical-ifindex    Flags    Remote
 Vtep Addrs

172.16.1.1      00:03:44 0050.7966.6806   10 Ethernet1/3         L

下方展示了Leaf-2的ARP缓存抑制表；

Leaf-2# show ip arp suppression-cache detail 
Flags: + - Adjacencies synced via CFSoE
       L - Local Adjacency
       R - Remote Adjacency
       L2 - Learnt over L2 interface
       PS - Added via L2RIB, Peer Sync
       RO - Dervied from L2RIB Peer Sync Entry

Ip Address      Age      Mac Address    Vlan Physical-ifindex    Flags    Remote
 Vtep Addrs

172.16.1.1      00:03:01 0050.7966.6806   10 (null)              R        3.3.3.
3

4.2 ARP抑制验证

在PC3(172.16.1.3)上ping PC1(172.16.1.1)

PC3> ping 172.16.1.1
84 bytes from 172.16.1.1 icmp_seq=1 ttl=64 time=58.651 ms
84 bytes from 172.16.1.1 icmp_seq=2 ttl=64 time=52.082 ms
84 bytes from 172.16.1.1 icmp_seq=3 ttl=64 time=54.362 ms
84 bytes from 172.16.1.1 icmp_seq=4 ttl=64 time=67.275 ms
84 bytes from 172.16.1.1 icmp_seq=5 ttl=64 time=50.352 ms

这时本地VTEP Leaf-2能够应答ARP请求消息，因为它具有存储在ARP抑制缓存中的信息。因此，当主机首次加入网络时，它会发送一条GARP消息，以确保分配给它的IP地址是唯一的；
由于ARP表或ARP抑制高速缓存都没有关于要求的IP-mac绑定的条目，因此该消息将泛洪到其他VTEP叶子交换机。但在这些表完成更新后，下次主机间通讯时无需再进行ARP请求泛洪；
下方展示了Leaf-2发送ARP回复消息的过程；

Leaf-2# 2020 Oct 13 21:02:00.100412 arp: arp_process_receive_packet_msg: VINCI: Anycast Proxy mode  
2020 Oct 13 21:02:00.100797 arp: arp_cache_resolve_l3_addr: arp_cache_resolve_l3_addr 
2020 Oct 13 21:02:00.101111 arp: arp_cache_resolve_l3_addr: mac: 0050.7966.6806, phy-ifindex:0x0, is_local:FALSE 
2020 Oct 13 21:02:00.101405 arp: arp_process_packet_in_l3_mode: ARP request: iod: 139, Vlan: 10, Dest-ip: 172.16.1.1, Mac-Addr: 0050.7966.6806, ifindex: 0x0, is_local: FALSE 
2020 Oct 13 21:02:00.101802 arp: arp_send_response_internal: ARP response from 172.16.1.1 to 172.16.1.3 on Vlan10, phy iod Ethernet1/4, vlan 10, svi_flag: 1 
2020 Oct 13 21:02:00.101867 arp: arp_send_response_internal: arp_send_response_internal: VINCI: is_flood: 0, iod: 139 phyiod: 10 
2020 Oct 13 21:02:00.101953 arp: arp_send_packet: Packet for 0050.7966.6808/172.16.1.3, iod 139(Vlan10), phy_iod 10(Ethernet1/4), phy_is_mct 0, flood_bd 0, flood port 1, skip_unnumbered_flood 0

4.3 同VRF，不同VNI下的主机互通

关于同VNI下主机互通已在上篇展示，本篇不再展示；
本节以PC1(172.16.1.1) ping PC2(172.162.2.)为例。

4.3.1 Leaf-1的VNI内交换

因为目标IP地址在另一个子网中，所以PC1使用Anycast Gateway MAC(AGM) 1234.1234.1234作为目标MAC地址，PC1向其默认网关Leaf-1发送ICMP请求消息，可参考下图；

image.png

4.3.2 Leaf-1上将数据包从L2VNI 10010路由到L3VNI 13960

本地VTEP交换机Leaf-1接收帧。目标IP地址172.16.2.2(主机PC3)是通过BGP学习的，并与下一跳IP地址4.4.4.4(Leaf-2)一起装载进RIB中，并在数据平面中也封装了其他信息，例如L3VNI和封装类型；
Leaf-1对下一跳地址进行递归路由查找，封装原始数据包并加上包含VNI ID(13960)的VxLAN包头，并通过Spine-1和Spine2将数据包路由到Leaf-2(外层MAC地址属于Spine-1和Spine-2)；
因为VxLAN属于MAC in UDP封装类型，所以必须有内层源MAC地址和目标MAC地址。内层源MAC地址是从Inter-VNI路由中使用的SVI(SVI VLAN 3960)中获取的，内层目标地址是BGP扩展团体通过BGP更新接收到的RMAC。

4.3.3 Leaf-2上将数据包从L3VNI 13960路由到L2VNI 10020

当VTEP交换机Leaf-2收到VxLAN封装的数据包时，它将拆掉VxLAN包头。由于VNI 13960已关联到VRF ta，因此路由决策基于VRF ta的RIB;
Leaf-2将原始ICMP请求路由到VLAN 20，并通过接口E1/3转发出去；
以上过程描述了对称式集成路由与桥接(IRB)模型，其中数据包首先由本地VTEP交换，然后通过使用VxLAN包头中的公用L3VNI在VxLAN Fabric中进行路由。接收方VTEP交换机收到数据包后拆掉VxLAN封装，并根据原始IP数据包的目标IP地址做出路由决策。在路由选择决定之后，数据包被转发到目的地(bridge-route-route-bridge)，数据包回程遵循相同的模型；
使用对称式IRB提供了设计上的灵活性，因为与非对称式IRB不同，无需将所有VNI配置到所有的VTEP交换机。非对称式IRB基于"bridge-route-bridge"模型，其中没有公用的L3VNI用于VNI间路由。例如：如果我们在VxLAN Fabric中使用非对称式IRB，则主机PC1会将数据包发送至默认网关(bridge部分)，就像在对称式IRB中一样。本地VTEP交换机Leaf-1做出路由决策，但不是使用的公用L3VNI，而是使用VxLAN包头中的VNI 10020，该包头关联到VLAN 20(VNI 10020关联的VLAN)，这是“route”部分。接收方VTEP交换机Leaf-2收到数据包后拆掉VxLAN包头，并基于VxLAN 10020将数据包转发至VLAN 20，最终到达主机PC3。
测试PC1 ping PC3，并在Spine与Leaf之间抓包，下方展示了抓包结果；

image.png

以上说明了如何在VxLAN Fabric中传播主机的IP地址以及如何将其装载进L3RIB中。

五、总结

image.png

六、引用参考

膜拜大佬：Toni Pasanen
https://nwktimes.blogspot.com/2018/05/vxlan-part-vii-vxlan-bgp-evpn-control.html

6 基于BGP EVPN实现Cisco VxLAN控制层面之MAC-IP学习和主机路由通告

一、说明

二、拓扑

三、控制层面操作

3.1 MAC-IP学习过程

3.1.1 本端VTEP的ARP学习

3.1.2 本端VTEP的MAC-IP

3.1.3 本端VTEP的BGP路由导出

3.1.4 远端VTEP的BGP路由导入

3.1.5 远端VTEP的IP VRF

3.2 ARP抑制

3.2.1 配置Leaf交换机：启用ARP抑制

3.2.2 查看ARP抑制缓存

3.2.3 抑制场景对比：

3.3 主机路由通告：VNI间路由(L3VNI)

3.3.1 本端VTEP RIB中的主机路由

3.3.2 本端VTEP上BGP进程中的主机路由

3.3.3 远端VTEP上BGP进程中的主机路由

3.3.4 将主机路由装载进远端VTEP的RIB

四、数据层面操作

4.1 ARP抑制过程

4.2 ARP抑制验证

4.3 同VRF，不同VNI下的主机互通

4.3.1 Leaf-1的VNI内交换

4.3.2 Leaf-1上将数据包从L2VNI 10010路由到L3VNI 13960

4.3.3 Leaf-2上将数据包从L3VNI 13960路由到L2VNI 10020

五、总结

六、引用参考

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