使用mtrace V2排除组播故障

简介

本文档介绍Cisco IOS^®XR中的mtrace版本2。

先决条件

要求

本文档没有任何特定的要求。

使用的组件

本文档特定于Cisco IOS^®XR，但不限于特定的软件版本或硬件。

本文档中的信息都是基于特定实验室环境中的设备编写的。本文档中使用的所有设备最初均采用原始（默认）配置。如果您使用的是真实网络，请确保您已经了解所有命令的潜在影响。

比较mtrace v1和mtrace v2

• mtrace v2 Reply message等同于mTrace v1 Response message。
• mtrace v1仅支持IPv4组播。mTrace v2支持IPv4和IPv6组播。
• mtrace v1查询和响应消息是IGMP消息。所有mTrace v2数据包都是UDP。
• mtrace v1有一个路由协议字段，路由协议是用于流向上游路由器的RPF的组播路由协议。mTrace v2有两个字段：一个用于用于RPF的单播路由协议，一个用于运行到上游路由器的组播路由协议。
• mtrace v1和v2的目标相同，数据包语法也非常相似。
• mtrace v1和v2对路由协议和转发代码使用不同的代码集。
• mtrace v2支持地址系列IPv6和特定UDP端口号(33435)。

mtrace v2详细信息

• 该工具允许跟踪从源到目的地的路径。它可验证采用的路径，也可能会指示任何问题，例如生存时间(TTL)或反向路径转发(RPF)。 
• mtrace v2和v1的目标相同。mtrace验证路径的方法是将数据包发送到目的地（最后一跳路由器或LHR），然后向后追踪通往源（源树）或Rendez-Vous Point (RP)路由器的路径。这意味着您必须指定目标（单播地址）、源（单播地址）和组播组。
• mtrace功能的真正强大之处在于，可以从网络中的任何路由器（发起方）执行mtrace命令。它不需要是第一跳路由器(FHR)或RP。

• mtrace v2在RFC 8487中指定：mtrace版本2：用于IP组播的traceroute设施
• mtrace v1on IOS-XR基于草案：draft-ietf-idmr-traceroute-ipm
• mtrace v2不支持mVPN

有三种类型的数据包用于mtrace。这三个数据包一起使mtrace起作用。发起方向最后一跳路由器发送mtrace查询数据包。此LHR将查询转换为请求数据包。然后，此数据包将逐跳单播转发到上游路由器。LHR和每个上游路由器都会添加一个响应数据块，其中包含接口地址、路由协议、转发代码等有用信息。当请求到达FHR时，它会将请求转换为应答数据包并将其转发给发起方。如果没有完成跟踪，中间路由器可能还会将回复返回到发起方，例如发生了致命错误，如“no route”。

请查看此映像，了解该过程以及三种mtrace数据包类型的处理。

发起方是R-10。LHR是LHR-4。FHR是FHR-3。RP是RP-5。网络正在运行PIM稀疏模式或任何源组播(ASM)。

mtrace请求消息如下所示。

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |           Length              |    # Hops     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                      Multicast Address                        |
     |                                                               |
     +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
     |                                                               |
     |                        Source Address                         |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                    Mtrace2 Client Address                     |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |            Query ID           |         Client Port #         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

客户端地址是发起方的地址，即执行mTrace v2命令的路由器。

响应数据块保存感兴趣的信息。此信息将添加到请求消息中。每台路由器都会向请求消息添加一个响应数据块。以下是响应数据块。

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |     Type      |           Length              |      MBZ      |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Query Arrival Time                       |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Incoming Interface Address                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                  Outgoing Interface Address                   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Upstream Router Address                     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .           Input packet count on Incoming Interface            .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .           Output packet count on Outgoing Interface           .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     .      Total number of packets for this source-group pair       .
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Rtg Protocol         |    Multicast Rtg Protocol     |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Fwd TTL    |      MBZ      |S|   Src Mask  |Forwarding Code|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

此响应块信息用于显示traceroute输出。每个响应块在mtrace输出中为一行。

路由协议和组播路由协议编号与IP组播MIB (RFC 5132)中的ipMcastRouteRtProtocol的值相同。它们与mtrace v1中使用的值不同。

IANA将其列出如下：

路由协议:

other     (1),  -- not specified
local     (2),  -- local interface
netmgmt   (3),  -- static route
icmp      (4),  -- result of ICMP Redirect

-- the following are all dynamic

-- routing protocols

egp        (5),  -- Exterior Gateway Protocol
ggp        (6),  -- Gateway-Gateway Protocol
hello      (7),  -- FuzzBall HelloSpeak
rip        (8),  -- Berkeley RIP or RIP-II
isIs       (9),  -- Dual IS-IS
esIs       (10), -- ISO 9542
ciscoIgrp  (11), -- Cisco IGRP
bbnSpfIgp  (12), -- BBN SPF IGP
ospf       (13), -- Open Shortest Path First
bgp        (14), -- Border Gateway Protocol
idpr       (15), -- InterDomain Policy Routing
ciscoEigrp (16), -- Cisco EIGRP
dvmrp      (17), -- DVMRP
rpl        (18), -- RPL [RFC-ietf-roll-rpl-19]
dhcp       (19), -- DHCP [RFC2132]

组播路由协议：

other(1),          -- none of the following
local(2),          -- e.g., manually configured
netmgmt(3),        -- set via net.mgmt protocol
dvmrp(4),
mospf(5),
pimSparseDense(6), -- PIMv1, both DM and SM
cbt(7),
pimSparseMode(8),  -- PIM-SM
pimDenseMode(9),   -- PIM-DM
igmpOnly(10),
bgmp(11),
msdp(12)

mtrace v2的转发代码如下所示。它们与mtrace v1中的不同。

   Value  Name            Description
   -----  --------------  ----------------------------------------------
   0x00   NO_ERROR        No error.
   0x01   WRONG_IF        Mtrace2 Request arrived on an interface
                          for which this router does not perform
                          forwarding for the specified group to the
                          source or RP.
   0x02   PRUNE_SENT      This router has sent a prune upstream that
                          applies to the source and group in the
                          Mtrace2 Request.
   0x03   PRUNE_RCVD      This router has stopped forwarding for this
                          source and group in response to a Request
                          from the downstream router.
   0x04   SCOPED          The group is subject to administrative
                          scoping at this router.
   0x05   NO_ROUTE        This router has no route for the source or
                          group and no way to determine a potential
                          route.
   0x06   WRONG_LAST_HOP  This router is not the proper LHR.
   0x07   NOT_FORWARDING  This router is not forwarding this source and
                          group out the Outgoing Interface for an
                          unspecified reason.
   0x08   REACHED_RP      Reached the Rendezvous Point.
   0x09   RPF_IF          Mtrace2 Request arrived on the expected
                          RPF interface for this source and group.
   0x0A   NO_MULTICAST    Mtrace2 Request arrived on an interface
                          that is not enabled for multicast.
   0x0B   INFO_HIDDEN     One or more hops have been hidden from this
                          trace.
   0x0C   REACHED_GW      Mtrace2 Request arrived on a gateway (e.g.,
                          a NAT or firewall) that hides the
                          information between this router and the
                          Mtrace2 client.
   0x0D   UNKNOWN_QUERY   A non-transitive Extended Query Type was
                          received by a router that does not support
                          the type.
   0x80   FATAL_ERROR     A fatal error is one where the router may
                          know the upstream router but cannot forward
                          the message to it.
   0x81   NO_SPACE        There was not enough room to insert another
                          Standard Response Block in the packet.
   0x83   ADMIN_PROHIB    Mtrace2 is administratively prohibited.

ios-XR上的MTRACE v2

命令的语法

使用率: mtrace <src_addr> [<dest_addr>] [<group_addr>] [<resp_addr>] [<ttl>]

确保指定2以使用mtrace v2。

RP/0/RP0/CPU0:R-10#mtrace?
mtrace  mtrace2 

RP/0/RP0/CPU0:R-10#mtrace2 ?
  ipv4  IPv4 Address family
  ipv6  ipv6 Address Family

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 ?
  Hostname or A.B.C.D  Source to trace route from
  <cr>         

源地址是发起方的地址。  

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.3 ?
  Hostname or A.B.C.D  Destination of route
  debug                Mtrace client-side debugging(cisco-support)
  <cr>           

目的地址是LHR的地址。

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.3 10.2.4.4 ?
  Hostname or A.B.C.D  Group to trace route via
  debug                Mtrace client-side debugging(cisco-support)
  <cr>         

组地址是正在跟踪的组播流的组地址。

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.3 10.2.4.4 225.1.1.1 ?
  Hostname or A.B.C.D  response address to receive response
  debug                Mtrace client-side debugging(cisco-support)
  <cr>       

响应地址是traceroute回复所返回的地址。    

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.3 10.2.4.4 225.1.1.1 10.0.0.10 ?
  <1-255>  Time-to-live for multicasted trace request
  debug    Mtrace client-side debugging(cisco-support)
  <cr>     

Examples

请注意，该命令可从网络中的任何路由器（不一定是启用PIM/组播的路由器）或正在调查的特定共享或源树启动。

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.3 10.2.4.4 225.1.1.1 10.0.0.10      
Type escape sequence to abort.

Mtrace from 10.1.3.3 to 10.2.4.4 
via group 225.1.1.1
From source (?) to destination (?)
Querying full reverse path... 

 0  10.2.4.4
-1  10.4.7.4 PIM  [10.1.3.0/24]
-2  10.5.7.7 PIM  [10.1.3.0/24]
-3  0.0.0.0 PIM Reached RP/Core [10.1.3.0/24]

您可以看到已对共享树(*，G)执行mtrace。mtrace从最后一跳路由器10.2.4.4开始，然后返回到RP (10.0.0.5)的共享树。原因是对于组225.1.1.1的源10.1.3.3，LHR-4路由器没有(S，G) MRIB条目。

[10.1.3.0/24]部分是用于RPF信息的单播路由。对于IPv4，IOS-XR中的RPF信息始终为/32条目。此信息来自单播路由。将显示此单播路由。

显示的是组播协议。这是PIM。

跳数显示反向，从最后一跳路由器的0开始，到到达第一跳路由器为止一直为负。

接下来是源树的情况。

RP/0/RP0/CPU0:LHR-4#show mrib route 225.1.1.1

IP Multicast Routing Information Base
Entry flags: L - Domain-Local Source, E - External Source to the Domain,
    C - Directly-Connected Check, S - Signal, IA - Inherit Accept,
    IF - Inherit From, D - Drop, ME - MDT Encap, EID - Encap ID,
    MD - MDT Decap, MT - MDT Threshold Crossed, MH - MDT interface handle
    CD - Conditional Decap, MPLS - MPLS Decap, EX - Extranet
    MoFE - MoFRR Enabled, MoFS - MoFRR State, MoFP - MoFRR Primary
    MoFB - MoFRR Backup, RPFID - RPF ID Set, X - VXLAN
Interface flags: F - Forward, A - Accept, IC - Internal Copy,
    NS - Negate Signal, DP - Don't Preserve, SP - Signal Present,
    II - Internal Interest, ID - Internal Disinterest, LI - Local Interest,
    LD - Local Disinterest, DI - Decapsulation Interface
    EI - Encapsulation Interface, MI - MDT Interface, LVIF - MPLS Encap,
    EX - Extranet, A2 - Secondary Accept, MT - MDT Threshold Crossed,
    MA - Data MDT Assigned, LMI - mLDP MDT Interface, TMI - P2MP-TE MDT Interface
    IRMI - IR MDT Interface, TRMI - TREE SID MDT Interface, MH - Multihome Interface

(*,225.1.1.1) RPF nbr: 10.4.7.7 Flags: C RPF
  Up: 1d21h
  Incoming Interface List
    GigabitEthernet0/0/0/1 Flags: A NS, Up: 1d21h
  Outgoing Interface List
    GigabitEthernet0/0/0/0 Flags: F NS LI, Up: 1d21h

(10.1.3.1,225.1.1.1) RPF nbr: 10.4.9.9 Flags: RPF
  Up: 1d18h
  Incoming Interface List
    GigabitEthernet0/0/0/2 Flags: A, Up: 1d18h
  Outgoing Interface List
    GigabitEthernet0/0/0/0 Flags: F NS, Up: 1d18h

存在源10.1.3.1的MRIB条目。完成该源时，mtrace命令将显示不同的输出。

RP/0/RP0/CPU0:R-10#mtrace2 ipv4 10.1.3.1 10.2.4.4 225.1.1.1 10.0.0.10  
Type escape sequence to abort.

Mtrace from 10.1.3.1 to 10.2.4.4 
via group 225.1.1.1
From source (?) to destination (?)
Querying full reverse path... 

 0  10.2.4.4
-1  10.4.9.4 PIM  [10.1.3.0/24]
-2  10.8.9.9 PIM  [10.1.3.0/24]
-3  10.3.8.8 PIM  [10.1.3.0/24]
-4  10.1.3.3 PIM  [10.1.3.0/24]

请注意，反向路径现在为LHR4 - IR-9 - IR-8 - FHR-3。这是从FHR-3到LHR-4的源树。这与(S，G)的MRIB条目匹配。

RP/0/RP0/CPU0:FHR-3#show mrib route 225.1.1.1

IP Multicast Routing Information Base
Entry flags: L - Domain-Local Source, E - External Source to the Domain,
    C - Directly-Connected Check, S - Signal, IA - Inherit Accept,
    IF - Inherit From, D - Drop, ME - MDT Encap, EID - Encap ID,
    MD - MDT Decap, MT - MDT Threshold Crossed, MH - MDT interface handle
    CD - Conditional Decap, MPLS - MPLS Decap, EX - Extranet
    MoFE - MoFRR Enabled, MoFS - MoFRR State, MoFP - MoFRR Primary
    MoFB - MoFRR Backup, RPFID - RPF ID Set, X - VXLAN
Interface flags: F - Forward, A - Accept, IC - Internal Copy,
    NS - Negate Signal, DP - Don't Preserve, SP - Signal Present,
    II - Internal Interest, ID - Internal Disinterest, LI - Local Interest,
    LD - Local Disinterest, DI - Decapsulation Interface
    EI - Encapsulation Interface, MI - MDT Interface, LVIF - MPLS Encap,
    EX - Extranet, A2 - Secondary Accept, MT - MDT Threshold Crossed,
    MA - Data MDT Assigned, LMI - mLDP MDT Interface, TMI - P2MP-TE MDT Interface
    IRMI - IR MDT Interface, TRMI - TREE SID MDT Interface, MH - Multihome Interface

(10.1.3.1,225.1.1.1) RPF nbr: 10.1.3.1 Flags: RPF
  Up: 1d21h
  Incoming Interface List
    GigabitEthernet0/0/0/0 Flags: A, Up: 1d21h
  Outgoing Interface List
    GigabitEthernet0/0/0/2 Flags: F NS, Up: 1d18h

您可以将debug IGMP与mtrace v1一起使用，以便在跟踪路径上的任何路由器上显示mTrace数据包。mtrace v2使用UDP数据包，因此IGMP调试不能用于mtrace v2。

但是，您可以重点关注IOS-XR上的mtrace v2数据包所使用的UDP端口33433。

示例：

在中间路由器上调试UDP mtracev2数据包。

IR-9：

RP/0/RP0/CPU0:IR-9#show access-lists 

ipv4 access-list mtracev2
 10 permit udp any eq 33433 any eq 33433

RP/0/RP0/CPU0:IR-9#debug udp packet v4-access-list mtracev2 location 0/RP0/CPU0 

RP/0/RP0/CPU0:IR-9#show debug                                

####  debug flags set from tty 'con0_RP0_CPU0'  ####
udp packet flag is ON with value '0x1:0x0:0x4:mtracev2:0x0:::'

RP/0/RP0/CPU0:IR-9#RP/0/RP0/CPU0:IR-9#

RP/0/RP0/CPU0:IR-9#

RP/0/RP0/CPU0:Jun 19 07:20:13.123 UTC: syslog_dev[115]: udp[214] PID-22001: R 42469 ms LEN 60    10.4.9.4:33433 <-> 10.4.9.9:33433
RP/0/RP0/CPU0:Jun 19 07:20:13.123 UTC: syslog_dev[115]: udp[214] PID-22001:  
RP/0/RP0/CPU0:Jun 19 07:20:13.139 UTC: syslog_dev[115]: udp[214] PID-22062: S    15 ms LEN 100   10.8.9.9:33433 <-> 10.8.9.8:33433 
RP/0/RP0/CPU0:Jun 19 07:20:13.139 UTC: syslog_dev[115]: udp[214] PID-22062:  

中间路由器接收并发送mtrace v2消息。

备注

确保您知道哪些路由器是FHR和LHR。其他路由器无法完成mtrace。

如果路由器已同步时钟，由于存在时间戳，您可以测量传播mtrace消息所需的时间。此时间仅用于指示，因为这些消息在每一跳都被视为控制消息。