為具有故障情況的多個站點之間的同一VPN配置重疊IP
簡介
本文檔描述了在SD-WAN重疊的多個站點中同一VPN中地址空間重疊的情況。它描述了示例網路、正常/故障轉移場景中的流量行為、配置和驗證。
必要條件
需求
Cisco建議您瞭解SD-WAN。
採用元件
本文中的資訊係根據以下軟體和硬體版本：
- SD-WAN控制器版本20.6.3
-
Cisco IOS® XE（在控制器模式下運行）17.6.3a
- 主機裝置(CSR1000V)17.3.3
本文中的資訊是根據特定實驗室環境內的裝置所建立。文中使用到的所有裝置皆從已清除（預設）的組態來啟動。如果您的網路運作中，請確保您瞭解任何指令可能造成的影響。
背景資訊
您可以在此處找到本文中使用的縮寫詞清單。
- 安全網際網路閘道 — SIG
- 虛擬路由和轉送 — VRF
- 虛擬私人網路 — VPN
- 直接網際網路接入 — DIA
- 網路位址轉譯 — NAT
- 多重協定標籤交換 — MPLS
- 服務端網路位址轉譯 — SS-NAT
- 資料中心 — 資料中心
- 重疊管理通訊協定 — OMP
- 網際網路通訊協定 — IP
有關服務端NAT：服務端NAT的詳細資訊，請參閱思科文檔
網路圖表
在此特定拓撲中，有1個DC（DC只有MPLS傳輸，但在實際場景中可能有多個傳輸）和2個分支位置，它們通過MPLS和網際網路傳輸連線到SD-WAN重疊。所有位置都配置了服務VPN 10。分支機構將SIG隧道（主要和備份）配置為Zscaler。DIA針對特定目標IP進行配置，以繞過擴展器。如果分支機構出現網際網路鏈路故障，則所有流量必須通過MPLS傳輸傳送到DC。
eBGP在服務VPN 10上配置，DC端有Zscaler路由器。DC路由器從Zscaler路由器接收預設路由，並將其重分配到OMP中。
規格
- 利用服務端VPN 10上Branch 1和Branch 2的重疊IP地址。
- 在典型場景中，當MPLS和網際網路傳輸啟動時，來自VPN 10的流量必須通過SIG隧道退出。
- 對於特定IP目標字首，流量必須繞過SIG隧道並通過DIA退出。
- 在網際網路鏈路發生故障的情況下，來自VPN 10的所有網際網路繫結流量必須通過DC退出。
解決方案
為了達到此要求，使用了SD-WAN功能服務端NAT和帶資料的DIA策略。
- 在每個分支路由器上使用不同的NAT池IP地址配置服務端NAT。
- 在流量傳送到SD-WAN重疊時，如果出現網際網路鏈路故障，會將源IP通過NAT從配置的NAT池轉換到IP地址。
- DC路由器看到重疊子網的NAT後地址。
設定
Branch-1配置
Branch-1路由器的配置如下。
vrf definition 10
rd 1:10
!
address-family ipv4
route-target export 1:10
route-target import 1:10
exit-address-family
!
interface GigabitEthernet2
description "Internet TLOC"
ip address 198.51.100.1 255.255.255.0
ip nat outside
!
interface GigabitEthernet3
description "MPLS TLOC"
ip address 172.20.1.10 255.255.255.0
!
interface GigabitEthernet4
description "Service Side VPN 10"
vrf forwarding 10
ip address 192.168.10.1 255.255.255.0
!
interface Tunnel2
ip unnumbered GigabitEthernet2
tunnel source GigabitEthernet2
tunnel mode sdwan
!
interface Tunnel3
ip unnumbered GigabitEthernet3
tunnel source GigabitEthernet3
tunnel mode sdwan
!
interface Tunnel100512
ip address 10.10.1.1 255.255.255.252
tunnel source GigabitEthernet2
tunnel destination 203.0.113.1
tunnel vrf multiplexing
!
interface Tunnel100513
ip address 10.10.1.5 255.255.255.252
tunnel source GigabitEthernet2
tunnel destination 203.0.113.2
tunnel vrf multiplexing
!
ip sdwan route vrf 10 0.0.0.0/0 tunnel active Tunnel100512 backup Tunnel100513
ip nat pool natpool1 172.16.2.1 172.16.2.2 prefix-length 30
ip nat inside source list nat-dia-vpn-hop-access-list interface GigabitEthernet2 overload
ip nat inside source list global-list pool natpool1 vrf 10 match-in-vrf overload
ip nat route vrf 10 192.0.2.1 255.255.255.255 global
!
ip route 0.0.0.0 0.0.0.0 198.51.100.100
ip route 0.0.0.0 0.0.0.0 172.20.1.100
!
分支2配置
Branch-2路由器的配置如下。
vrf definition 10
rd 1:10
!
address-family ipv4
route-target export 1:10
route-target import 1:10
exit-address-family
!
address-family ipv6
exit-address-family
!
interface GigabitEthernet2
description "Internet TLOC"
ip address 198.51.100.2 255.255.255.0
ip nat outside
!
!
interface GigabitEthernet3
description "MPLS TLOC"
ip address 172.20.1.20 255.255.255.0
!
interface GigabitEthernet4
description "Service Side VPN 10"
vrf forwarding 10
ip address 192.168.10.1 255.255.255.0
!
interface Tunnel2
ip unnumbered GigabitEthernet2
tunnel source GigabitEthernet2
tunnel mode sdwan
!
interface Tunnel3
ip unnumbered GigabitEthernet3
tunnel source GigabitEthernet3
tunnel mode sdwan
!
interface Tunnel100512
ip address 10.10.2.1 255.255.255.252
tunnel source GigabitEthernet2
tunnel destination 203.0.113.1
tunnel vrf multiplexing
!
interface Tunnel100513
ip address 10.10.2.5 255.255.255.252
tunnel source GigabitEthernet2
tunnel destination 203.0.113.2
tunnel vrf multiplexing
!
!
ip sdwan route vrf 10 0.0.0.0/0 tunnel active Tunnel100512 backup Tunnel100513
ip nat route vrf 10 192.0.2.1 255.255.255.255 global
ip nat pool natpool1 172.16.2.9 172.16.2.10 prefix-length 30
ip nat inside source list nat-dia-vpn-hop-access-list interface GigabitEthernet2 overload
ip nat inside source list global-list pool natpool1 vrf 10 match-in-vrf overload
!
ip route 0.0.0.0 0.0.0.0 198.51.100.100
ip route 0.0.0.0 0.0.0.0 172.20.1.100
!
DC-Router配置
DC路由器配置如下。
vrf definition 10
rd 1:10
!
address-family ipv4
route-target export 10:10
route-target import 10:10
exit-address-family
!
interface Tunnel2
ip unnumbered GigabitEthernet2
tunnel source GigabitEthernet2
tunnel mode sdwan
!
interface GigabitEthernet2
ip address 172.20.1.30 255.255.255.0
description "MPLS TLOC"
!
interface GigabitEthernet4
description "Service Side VPN 10"
vrf forwarding 10
ip address 172.31.19.19 255.255.255.252
!
router bgp 10
bgp log-neighbor-changes
distance bgp 20 200 20
!
address-family ipv4 vrf 10
redistribute omp
neighbor 172.31.19.20 remote-as 100
neighbor 172.31.19.20 activate
neighbor 172.31.19.20 send-community both
exit-address-family
!
!
ip route 0.0.0.0 0.0.0.0 172.20.1.100
!
vSmart策略
vSmart策略配置如下。
data-policy _VPN10-VPN20_1-Branch-A-B-Central-NAT-DIA
vpn-list VPN10
sequence 1
match
source-ip 192.168.10.0/24
!
action accept
nat pool 1
!
default-action accept
!
site-list BranchA-B
site-id 11
site-id 22
!
site-list DC
site-id 33
!
vpn-list VPN10
vpn 10
!
prefix-list _AnyIpv4PrefixList
ip-prefix 0.0.0.0/0 le 32
!
apply-policy
site-list BranchA-B
data-policy _VPN10_1-Branch-A-B-Central-NAT-DIA from-service
!
故障轉移方案
Branch-1流量正常案例
當兩個傳輸均開啟時（如輸出所示），預設情況下，流量會透過主SIG通道退出 Tunnel100512. 主通道關閉時，流量會交換到備份通道 Tunnel100513.
Branch-1#show ip route vrf 10
Routing Table: 10
<SNIP>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
S* 0.0.0.0/0 [2/0], Tunnel100512
192.0.2.0/32 is subnetted, 1 subnets
n Nd 192.0.2.1 [6/0], 3d02h, Null0
n Ni 172.16.2.0 [7/0], 3d04h, Null0
m 172.16.2.8 [251/0] via 172.31.31.2, 3d01h, Sdwan-system-intf
Branch-1#
Traceroute顯示流量通過SIG通道。
Host-BR-1#ping 192.0.2.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/49/101 ms
Host-BR-1#
Host-BR-1#traceroute 192.0.2.100 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.100
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.10.1 38 msec 7 msec 4 msec
2 203.0.113.1 79 msec * 62 msec
Host-BR-1#
到特定目的地的流量 192.0.2.1 通過DIA（NAT到WAN IP地址）退出。
Host-BR-1#ping 192.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/49/101 ms
Host-BR-1#
Branch-1#sh ip nat translation
Pro Inside global Inside local Outside local Outside global
icmp 198.51.100.1:1 192.168.10.10:1 192.0.2.1:1 192.0.2.1:1
Total number of translations: 1
Branch-1#
Branch-2流量正常案例
在Branch-2路由器上也觀察到類似行為。
Branch-2#show ip route vrf 10
Routing Table: 10
<SNIP>
Gateway of last resort is 0.0.0.0 to network 0.0.0.0
S* 0.0.0.0/0 [2/0], Tunnel100512
192.0.2.0/32 is subnetted, 1 subnets
n Nd 192.0.2.1 [6/0], 00:00:08, Null0
m 172.16.2.0 [251/0] via 172.31.31.1, 3d01h, Sdwan-system-intf
n Ni 172.16.2.8 [7/0], 3d04h, Null0
Branch-2#
Host-BR-2#ping 192.0.2.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/49/101 ms
Host-BR-2#
Host-BR-2#traceroute 192.0.2.100 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.100
VRF info: (vrf in name/id, vrf out name/id)
1 192.168.10.1 38 msec 7 msec 4 msec
2 203.0.113.1 79 msec * 62 msec
Host-BR-2#
Host-BR-2#ping 192.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/49/101 ms
Host-BR-2#
Branch-2#show ip nat translation
Pro Inside global Inside local Outside local Outside global
icmp 198.51.100.2:1 192.168.10.10:1 192.0.2.1:1 192.0.2.1:1
Total number of translations: 1
Branch-2#
故障方案
Branch-1故障場景
本節介紹Internet故障期間的行為。
Internet鏈路被管理性關閉以模擬Internet故障鏈路。
Branch-1#show sdwan control local-properties
<SNIP>
PUBLIC PUBLIC PRIVATE PRIVATE PRIVATE MAX
INTERFACE IPv4 PORT IPv4 IPv6 PORT VS/VM COLOR STATE CNTRL
---------------------------------------------------------------------------------------------------------------------
GigabitEthernet2 198.51.100.1 12346 198.51.100.1 :: 12346 1/0 biz-internet down
GigabitEthernet3 172.20.1.10 12346 172.20.1.10 :: 12346 1/1 mpls up
Branch-1#
輸出顯示，在Internet鏈路故障場景中，Branch-1路由器通過OMP從DC路由器接收預設路由。172.31.31.3是DC路由器的系統IP。
Branch-1#show ip route vrf 10
<SNIP>
Gateway of last resort is 172.31.31.3 to network 0.0.0.0
m* 0.0.0.0/0 [251/0] via 172.31.31.3, 00:01:17, Sdwan-system-intf
<SNIP>
目的地為 192.0.2.100 獲取到服務端NAT池的NAT並通過DC退出。
Host-BR-1#ping 192.0.2.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 10/37/103 ms
Host-BR-1#
Branch-1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 172.16.2.1:3 192.168.10.1:3 192.0.2.100:3 192.0.2.100:3
Total number of translations: 1
Branch-1#
Traceroute結果顯示流量採用DC路徑。172.20.1.30是DC路由器的MPLS傳輸WAN IP。
Host-BR-1#traceroute 192.0.2.100 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.100
1 192.168.10.1 26 msec 5 msec 3 msec
2 172.20.1.30 10 msec 5 msec 27 msec
<SNIP>
Branch-1#show sdwan bfd sessions
SOURCE TLOC REMOTE TLOC DST PUBLIC DST PUBLIC DETECT TX
SYSTEM IP SITE ID STATE COLOR COLOR SOURCE IP IP PORT ENCAP MULTIPLIER INTERVAL(msec) UPTIME TRANSITIONS
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
172.31.31.2 22 up mpls mpls 172.20.1.10 172.20.1.20 12406 ipsec 7 1000 0:14:56:54 0
172.31.31.3 33 up mpls mpls 172.20.1.10 172.20.1.30 12406 ipsec 7 1000 0:14:56:57 0
Branch-1#
目的地為特定IP 192.0.2.1的流量也會通過NAT傳送到服務端NAT池，並通過DC退出。
Host-BR-1#ping 192.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 10/37/103 ms
Host-BR-1#
Branch-1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 172.16.2.1:4 192.168.10.10:4 192.0.2.1:4 192.0.2.1:4
Total number of translations: 1
Branch-1#
Host-BR-1#traceroute 192.0.2.1 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.1
1 192.168.10.1 26 msec 5 msec 3 msec
2 172.20.1.30 10 msec 5 msec 27 msec
<SNIP>
從vSmart推送的資料策略配置：
Branch-1#show sdwan policy from-vsmart
from-vsmart data-policy _VPN10-VPN20_1-Branch-A-B-Central-NAT-DIA
direction from-service
vpn-list VPN10
sequence 1
match
source-ip 192.168.10.0/24
action accept
count NAT_VRF10_BRANCH_A_B_-968382210
nat pool 1
!
from-vsmart lists vpn-list VPN10
vpn 10
!
Branch-1#
Branch-1#show run | sec "natpool1"
<SNIP>
ip nat pool natpool1 172.16.2.1 172.16.2.2 prefix-length 30
Branch-2故障場景
發生網際網路故障切換時，在Branch-2路由器上也觀察到類似行為。
Branch-2#show sdwan control local-properties
<SNIP>
PUBLIC PUBLIC PRIVATE PRIVATE PRIVATE MAX
INTERFACE IPv4 PORT IPv4 IPv6 PORT VS/VM COLOR STATE CNTRL
---------------------------------------------------------------------------------------------------------------------
GigabitEthernet2 198.51.100.2 12346 198.51.100.2 :: 12346 1/0 biz-internet down
GigabitEthernet3 172.20.1.20 12346 172.20.1.20 :: 12346 1/1 mpls up
Branch-2#
Branch-2#show ip route vrf 10
<SNIP>
Gateway of last resort is 172.31.31.3 to network 0.0.0.0
m* 0.0.0.0/0 [251/0] via 172.31.31.3, 00:10:17, Sdwan-system-intf
<SNIP>
Host-BR-2#ping 192.0.2.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.100, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 10/37/103 ms
Host-BR-2#
Branch-2#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 172.16.2.9:3 192.168.10.1:3 192.0.2.100:3 192.0.2.100:3
Total number of translations: 1
Branch-2#
Host-BR-2#traceroute 192.0.2.100 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.100
1 192.168.10.1 26 msec 5 msec 3 msec
2 172.20.1.30 10 msec 5 msec 27 msec
<SNIP>
Host-BR-2#ping 192.0.2.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 10/37/103 ms
Host-BR-2#
Branch-2#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 172.16.2.9:4 192.168.10.10:4 192.0.2.1:4 192.0.2.1:4
Total number of translations: 1
Branch-2#
Host-BR-2#traceroute 192.0.2.1 numeric
Type escape sequence to abort.
Tracing the route to 192.0.2.1
1 192.168.10.1 26 msec 5 msec 3 msec
2 172.20.1.30 10 msec 5 msec 27 msec
<SNIP>
Branch-2#show sdwan policy from-vsmart
from-vsmart data-policy _VPN10-VPN20_1-Branch-A-B-Central-NAT-DIA
direction from-service
vpn-list VPN10
sequence 1
match
source-ip 192.168.10.0/24
action accept
count NAT_VRF10_BRANCH_A_B_-968382210
nat pool 1
!
from-vsmart lists vpn-list VPN10-VPN20
vpn 10
!
Branch-2#
Branch-2#show run | sec "natpool1"
<SNIP>
ip nat pool natpool1 172.16.2.9 172.16.2.9 prefix-length 30
DC路由器路由狀態
路由表從DC路由器捕獲。
如輸出所示，DC路由器能夠使用 post-NAT IP源自 SS-NAT pool （172.16.2.0和172.16.2.8），而不是實際的LAN IP 192.168.10.0/24172.31.31.1 和 172.31.31.2 是 system-ip 為Branch-1/Branch-2配置。System-IP 172.31.31.10 屬於 vSmart.
DC-RTR#show ip route vrf 10
Routing Table: 10
<SNIP>
m 172.16.2.0 [251/0] via 172.31.31.1, 02:44:25, Sdwan-system-intf
m 172.16.2.8 [251/0] via 172.31.31.2, 02:43:33, Sdwan-system-intf
m 192.168.10.0[251/0] via 172.31.31.2, 03:01:35, Sdwan-system-intf
[251/0] via 172.31.31.1, 03:01:35, Sdwan-system-intf
DC-RTR#show sdwan omp routes
<SNIP> PATH ATTRIBUTE
VPN PREFIX FROM PEER ID LABEL STATUS TYPE TLOC IP COLOR ENCAP PREFERENCE
--------------------------------------------------------------------------------------------------------------------------------------
10 172.16.2.0/30 172.31.31.10 6 1002 C,I,R installed 172.31.31.1 mpls ipsec -
172.31.31.10 10 1002 Inv,U installed 172.31.31.1 biz-internet ipsec -
10 172.16.2.8/30 172.31.31.10 8 1002 C,I,R installed 172.31.31.2 mpls ipsec -
10 192.168.10.0/24 172.31.31.10 1 1002 C,I,R installed 172.31.31.1 mpls ipsec -
172.31.31.10 2 1002 C,I,R installed 172.31.31.2 mpls ipsec -
172.31.31.10 12 1002 Inv,U installed 172.31.31.1 biz-internet ipsec -
驗證
目前尚無適用於此組態的具體驗證程式。
疑難排解
目前尚無適用於此組態的具體疑難排解資訊。
其他資訊
案例1
在控制器運行於20.3.4版且cEdge運行相同配置的17.3.3a或更低版本的情況下，可以觀察到，在正常/故障轉移情況下，流量會通過NAT連線到服務端NAT池，並中斷流量。
cEdge捕獲：
Host-BR-1#ping 192.0.2.100
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.0.2.100, timeout is 2 seconds:
U.U.U
Success rate is 0 percent (0/5)
Host-BR-1#
Branch-1#show ip nat translations
Pro Inside global Inside local Outside local Outside global
icmp 172.16.2.1:3 192.168.10.1:3 192.0.2.100:3 192.0.2.100:3
Total number of translations: 1
Branch-1#
WOW-Branch-1#show run | sec "natpool1"
<SNIP>
ip nat pool natpool1 172.16.2.1 172.16.2.2 prefix-length 30
從17.3.3a版上運行的cEdge捕獲輸出。通過SIG隧道發往的流量通過NAT連線到SS-NAT池並被丟棄。從17.3.6版本開始提供修復程式。
案例2
要求(含UTD檢查的服務端NAT(SS-NAT))
假設使用者已請求以下要求：
1.當網際網路和MPLS傳輸均正常運行時，VPN 10中的無線客戶端可以定向到資料中心中的ISE進行身份驗證。此外，通過SD-WAN重疊傳輸的VPN 10流量可以接受檢查。由於此流量是重疊的一部分，VPN 10利用SS-NAT功能。[UTD + SS-NAT]
2.如果網際網路傳輸不可用，則來自VPN 10的所有流量（包括無線和有線流量）均可使用MPLS傳輸通過重疊進行路由。此流量也可能受到檢查。[UTD + SS-NAT]
這些要求旨在確保不同網路條件下分支機構1中VPN 10的安全和監控流量。
在上述兩種情況下，您都使用SS-NAT組合進行UTD檢測。以下是該場景的UTD配置示例。
policy utd-policy-vrf-10
all-interfaces
vrf 10
threat-inspection profile TEST_IDS_Policy
exit
警告：請注意，目前不支援UTD與SS-NAT的組合。因此，此組合併不按預期工作。未來版本中可能包含此問題的修補程式。
因應措施
解決方法是禁用重疊IP VPN（本例中為VPN 10）上的UTD策略並啟用全域性VPN。
註：此配置已在17.6版中測試和驗證。
policy utd-policy-vrf-global
all-interfaces
vrf global
threat-inspection profile TEST_IDS_Policy
exit
修訂記錄
| 修訂 | 發佈日期 | 意見 |
|---|---|---|
1.0 |
09-Oct-2023 |
初始版本 |
意見