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消息等同于mTrace v1 Response消息。
- 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，该路由协议是用于RPF到上游路由器的组播路由协议。mTrace v2有两个字段：一个用于RPF的单播路由协议，另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)。
注意：cisco IOS XR软件上的MTRACE v2使用非标准端口33433，而不是标准RFC端口33435。
mtrace v2详细信息
- 该工具可用于跟踪从源到目的地的路径。它可验证采用的路径，也可指出任何问题，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（上一跳路由器或LHR），并向后追踪通往源（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功能的真正力量在于，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。
- rfc 8487中规定了MTRACE v2: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。这三个数据包共同使mtrace正常工作。发起方向最后一跳路由器发送一个mtrace Query数据包。此LHR将查询转换为请求数据包。然后，此数据包被单播逐跳转发到上游路由器。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，它会将请求转换为回复数据包并将其转发给发起方。如果跟踪未完成，例如发生致命错误，如“no route”，中间路由器可能还会将应答返回到发起者。
请查看此映像，了解三种mtrace数据包类型的过程和处理。
发起方为R-10。LHR为LHR-4。FHR为FHR-3。RP为RP-5。网络运行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。
响应数据块包含感兴趣的信息。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。每个响应块都是mtrace输出中的一行。
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)
此处显示了mtrace v2的转发代码。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
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
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)
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)
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)
响应地址是traceroute应答返回的地址。
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)
Examples
请注意，命令可从网络中的任何路由器启动，但不一定是从启用了PIM/组播的路由器启动的，也不一定是从所调查的特定共享树或源树启动的。
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]
您可以看到已针对共享树(*,G)执行mtrace。 mtrace从最后一跳路由器10.2.4.4开始，然后在共享树上返回到RP(10.0.0.5)。 原因在于，LHR-4路由器没有为组225.1.1.1的源10.1.3.3设置(S，G)MRIB条目。
[10.1.3.0/24]部分是用于RPF信息的单播路由。IOS-XR中的RPF信息始终是IPv4的/32条目。此信息源自单播路由。将显示此单播路由。
显示了组播协议。这是PIM。
跳数以相反方式显示，从最后一跳路由器的0开始，一直变为负数，直到到达第一跳路由器。
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
有源10.1.3.1的MRIB条目。对该源执行mtrace命令后，该命令会显示不同的输出。
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。该路径与(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
可以将debug IGMPmtrace v1用于显示trace路径沿途任何路由器上的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mtrace v2数据包使用的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。其它路由器无法完成mtrace。
如果路由器已同步时钟，则由于存在时间戳，您可以测量传播mtrace消息所需的时间。此时间仅作指示，因为这些消息在每一跳都被视为控制消息。
修订历史记录
| 版本 | 发布日期 | 备注 |
|---|---|---|
1.0 |
01-Jul-2024 |
初始版本 |
反馈