應用典型組網
BFD和應用結合原理
在如上圖組網中,該場景主要用於TE tunnel的 HotStandBy 保護場景的快速切換。該場景的檢測目的是TE隧道內部主LSP是否可用。正常情況下,流量走主LSP。在主LSP上創建BFD會話,檢測該鏈路是否出現故障。當檢測到主LSP出現故障後,在轉發層就把流量切到備LSP 。在HotStandBy場景下,TE模塊會向底層下發兩條LSP信息,轉發平面根據底層表項中主LSP的狀態進行報文轉發,一旦主故障,BFD會將LSP down事件通過產品MSG ME模塊通告給588/2800,芯片將這主LSP表識為down,從而完成流量的切換。表項查詢過程如下:TunnelID->Tunnel Token->LSP status。故障前後表項狀態對比:
<code>[RT13]dis interface Tunnel 1/0/5
Tunnel1/0/5 current state : UP
Line protocol current state : UP
Last line protocol up time : 2010-08-28 14:37:42
Description:HUAWEI, Quidway Series, Tunnel1/0/5 Interface
Route Port,The Maximum Transmit Unit is 1500
Internet Address is unnumbered, using address of LoopBack0(10.8.8.1/32)
Encapsulation is TUNNEL, loopback not set
Tunnel destination 10.10.10.3
Tunnel up/down statistics 1
Tunnel protocol/transport MPLS/MPLS, ILM is available,
primary tunnel id is 0x200812a, secondary tunnel id is 0x0 //tunnel ID
300 seconds output rate 52808 bits/sec, 100 packets/sec
0 seconds output rate 0 bits/sec, 0 packets/sec
17767212 packets output, 1172698068 bytes
0 output error
[RT13]dis tu
[RT13]dis tunnel--in
[RT13]dis tunnel-in
[RT13]dis tunnel-info 200812a
Tunnel ID: 0x200812a
Tunnel Token: 298 //主lsp對應 token
Type: lsp
Destination: 10.10.10.3
Out Slot: 1
Instance ID: 0
Out Interface: GigabitEthernet1/0/2
Out Label: 3
Next Hop: 10.1.1.12
Lsp Index: 6172
[RT13-diagnose]efu mpls lsp_status query 1 298
-------------------- lsp status info ----------------
index is 298
value is 1 //故障前底層lsp 狀態1為UP,0為down
[RT13-diagnose]efu mpls lsp_status query 1 298
-------------------- lsp status info ----------------
index is 298
value is 0 //故障後,控制平面LSP沒有刪除前
[RT13-diagnose]display interface Tunnel 1/0/5
Tunnel1/0/5 current state : UP
Line protocol current state : UP
Last line protocol up time : 2010-08-28 14:37:42
Description:HUAWEI, Quidway Series, Tunnel1/0/5 Interface
Route Port,The Maximum Transmit Unit is 1500
Internet Address is unnumbered, using address of LoopBack0(10.8.8.1/32)
Encapsulation is TUNNEL, loopback not set
Tunnel destination 10.10.10.3
Tunnel up/down statistics 1
Tunnel protocol/transport MPLS/MPLS, ILM is available,
primary tunnel id is 0x0, secondary tunnel id is 0x0 //上層協議收斂後,當前tunnel走備份lsp,Tunnel ID 為 0
300 seconds output rate 46552 bits/sec, 83 packets/sec
0 seconds output rate 0 bits/sec, 0 packets/sec
18052440 packets output, 1191596192 bytes
0 output error
[RT13-diagnose]efu mpls lsp_status query 1 0
-------------------- lsp status info ----------------
index is 0
value is 1 // UP可用/<code>
需要注意的是當備份LSP也故障的話,Tunnel狀態為down,TnlM不會分配tnl ID。
該場景中BFD探測的對象是主LSP;產品MSG ME模塊將探測結果通告給轉發引擎588/2800,方法是將探測結果寫入表項;TEM 模塊負責 BFD session for lsp 和反向BFD session 創建。
BFD和應用推薦規格
TE隧道接入業務不同則,對故障感知也不同,對於語音業務,一般要求<200ms,對於上網業務,對故障感知要求在秒級就可以
典型應用局點
西班牙T局,有該場景應用。AC、AG設備間部署TE Tunnel熱備份業務(hot-standby),可以通過,通過在AC上配置 BFD for te lsp來達到業務毫秒級收斂,
配置過程
1、 在PE1上配置到PE2的TE tunnel,通過顯示路徑讓主隧道是PE1-P1-PE2,備份隧道為PE1-P2-PE2,如下:
<code>[RT13-Tunnel0/0/5]dis this
#
interface Tunnel0/0/5
ip address unnumbered interface LoopBack0
tunnel-protocol mpls te
destination 10.10.10.3
mpls te tunnel-id 5
mpls te record-route label
mpls te path explicit-path 13-11-12
mpls te path explicit-path 13-14-12 secondary
mpls te backup hot-standby
mpls te igp shortcut
mpls te igp metric absolute 1
mpls te commit
statistic enable
#
return
[RT13-Tunnel0/0/5] /<code>
2、 在MPLS視圖下使能mpls te bfd,在遠端BFD 視圖配置mpls-passive
<code>[RT13-mpls]dis this
#
mpls lsr-id 10.8.8.1
mpls
mpls te
mpls te bfd enable
mpls rsvp-te
mpls rsvp-te hello
mpls rsvp-te hello full-gr
mpls te cspf
#
[RT12-bfd]dis this
#
bfd
mpls-passive
# /<code>
3、 查看BFD session 建立情況,以及PST 位標示情況
<code>[RT13]display bfd session discriminator 8524 verbose
--------------------------------------------------------------------------------
Session MIndex : 16714 State : Up Name : dyn_8524
--------------------------------------------------------------------------------
Local Discriminator : 8524 Remote Discriminator : 8568
Session Detect Mode : Asynchronous Mode Without Echo Function
BFD Bind Type : TE_LSP
Bind Session Type : Dynamic
Bind Peer IP Address : 10.10.10.3
NextHop Ip Address : 10.1.1.12
Bind Interface : Tunnel0/0/5 TE LSP Type : Primary
Tunnel Id : 0xc006040a LSP Token : 0x2008120
FSM Board Id : 1 TOS-EXP : 7
Min Tx Interval (ms) : 10 Min Rx Interval (ms) : 10
Actual Tx Interval (ms): 10 Actual Rx Interval (ms): 10
Local Detect Multi : 3 Detect Interval (ms) : 30
Echo Passive : Disable Acl Number : -
Destination Port : 3784 TTL : 1
Proc Interface Status : Disable Process PST : Enable
WTR Interval (ms) : -
Active Multi : 3
Last Local Diagnostic : No Diagnostic
Bind Application : LSPM | L2VPN | TUNNEL_PS
Session TX TmrID : - Session Detect TmrID : -
Session Init TmrID : - Session WTR TmrID : -
Session Echo Tx TmrID : -
PDT Index : FSM-1000002 | RCV-2 | IF-1020000 | TOKEN-0
Session Description : -/<code>
4、 查看Tunnel接口狀態
<code>[RT13]display mpls te tunnel-interface Tunnel 0/0/5
Tunnel Name : Tunnel0/0/5
Tunnel State Desc : Primary CR-LSP Up and HotBackup CR-LSP Up
Tunnel Attributes :
Session ID : 5
Ingress LSR ID : 10.8.8.1 Egress LSR ID: 10.10.10.3
Admin State : UP Oper State : UP
Signaling Protocol : RSVP
Tie-Breaking Policy : None Metric Type : None
Car Policy : Disabled Bfd Cap : Enabled/<code>
配置說明:
配置BFD for LSP 在 HSB場景下使用,也可以通過配置相應靜態bfd session 來實現。不過在配置中需要注意需要手工使能pis 和pst標識。
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