tracert ipv6

Function

The tracert ipv6 command checks the path of packets from the source to the destination, checks IPv6 network connectivity, and locates a network fault.

Format

Only S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support -v.

Parameters

Parameter	Description	Value
-f first-hop-limit	Specifies the initial hop-limit. Carried in the IPv6 header, the hop-limit (time to live) indicates the lifetime of IPv6 packets and specifies the maximum number of hops that the IPv6 packets can pass through. The hop-limit field in IPv6 packets is similar to the TTL field in the IPv4 packets. The hop-limit value is set on the source and reduced by 1 each time the packet passes through a Layer 3 device. When the hop-limit value is reduced to 0 on a Layer 3 device, the Layer 3 device discards the packet and sends an ICMPv6 Timeout message to the source. If first-hop-limit is specified and the number of hops is smaller than the specified value, the hop-limit value will be greater than 0 after the packet passes through all the nodes. Therefore, no ICMPv6 Timeout message is sent to the source. If max-hop-limit is specified, the value of first-hop-limit must be smaller than the value of max-hop-limit.	The value is an integer that ranges from 1 to 255. The default value is 1.
-m max-hop-limit	Specifies the maximum hop-limit. Usually, the maximum hop-limit is set to the number of hops that a packet passes through. To change the hop-limit value, you need to use this parameter. If first-hop-limit is specified, the value of max-hop-limit must be greater than the value of first-hop-limit.	The value is an integer that ranges from 1 to 255. The default value is 30.
-p port-number	Specifies the UDP port number of the destination. If no UDP port number is specified for the destination, when you run the tracert ipv6 command, a port with the port number greater than 32768 is randomly chosen for the destination to receive tracert packets. Before specifying the UDP port number for the destination, ensure that the port is not in use; otherwise, the tracert fails.	The value is an integer that ranges from 1 to 65535. The default value is 33434.
-q probes	Specifies the number of tracert packets sent each time. In the case of poor network quality, you can set probes to a comparatively large value to ensure that tracert packets can reach the destination.	The value is an integer that ranges from 1 to 65535. The default value is 3.
-w timeout	Sets the timeout period to wait for a reply. If a tracert packet times out when reaching a gateway, an asterisk (*) is displayed. In the case of poor network quality and a low network transmission rate, you are advised to prolong the timeout period.	The value is an integer that ranges from 1 to 65535, in milliseconds. The default value is 5000.
vpn-instance vpn-instance-name	Specifies the name of a VPN instance for the IPv6 address family.	The value must be an existing VPN instance name.
-a source-ipv6-address	Specifies the source address of a tracert packet. If this parameter is not specified, the IP address of the outbound interface is used as the source IP address for sending tracert packets.	The value is a 32-digit hexadecimal number, in the format of X:X:X:X:X:X:X:X.
-s packetsize	Specifies the length of an ICMPv6 Echo Request message, excluding the IP header and ICMPv6 header.	The value is an integer that ranges from 20 to 9600, in bytes. The default value is 56.
-name	Displays the name of the destination host.	-
-v	Displays the MPLS label carried in the ICMP Time Exceeded packet.	By default, the MPLS label carried in the ICMP Time Exceeded is not displayed. Instead, only the path information carried in the ICMP Time Exceeded and Port-Unreachable packets is displayed.
host	Specifies the host name or IPv6 address of the destination host.	The value is a string of 1 to 255 case-sensitive characters, spaces not supported. When double quotation marks are used around the string, spaces are allowed in the string. The IPv6 address is a 32–bit string in hexadecimal format, namely, the format X:X:X:X:X:X:X:X.

Views

All views

Default Level

0: Visit level

Usage Guidelines

Usage Scenario

When a fault occurs on the network and the peer is an IPv6 device, you can run the ping ipv6 command to check network connectivity based on the reply message, and then run the tracert ipv6 command to locate the fault.

You can specify different parameters in the tracert ipv6 command for different scenarios:

To check information about nodes between the source and the IPv6 destination, run the tracert ipv6 host command.
To check information about nodes between the source and the IPv6 destination on a Layer 3 VPN, run the tracert ipv6 vpn-instance vpn-instance-name host command. On a Layer 3 VPN, devices may not have routing information about each other. Therefore, you cannot use the tracert ipv6 host command to check whether the peer is reachable. To check information about nodes between the source and the IPv6 destination in a specified VPN instance, run the tracert ipv6 vpn-instance vpn-instance-name host command.
On an unstable network, you can run the tracert ipv6 -q probes -w timeout host command to check information about nodes between the source and the IPv6 destination. If the network is unreliable, set the packet transmission count (-q) and timeout (-w) to the upper limits. This makes the test result accurate.
To check information about nodes along a segment of a path, run the tracert ipv6 -f first-hop-limit -m max-hop-limit host command that has initial hop-limit and maximum hop-limit specified.

Prerequisites

The UDP module of each node is working properly; otherwise, the IPv6 tracert operation fails.
The VPN module of each node is working properly if vpn-instance is specified.
The ICMPv6 module of each node is working properly; otherwise, " * * * " is displayed.

Procedure

The execution process of the tracert ipv6 command is as follows:

The source sends a packet with the hop-limit being 1. After the hop-limit times out, the first hop sends an ICMPv6 Error message to the source, indicating that the packet cannot be forwarded.
The source sends a packet with the hop-limit being 2. After the hop-limit times out, the second hop sends an ICMPv6 Error message to the source, indicating that the packet cannot be forwarded.
The source sends a packet with the hop-limit being 3. After the hop-limit times out, the third hop sends an ICMPv6 Error message to the source, indicating that the packet cannot be forwarded.
The preceding process proceeds until the packet reaches the destination.

When receiving an IPv6 packet, each destination hop cannot find the port specified in the IPv6 packet, and therefore returns an ICMPv6 Port Unreachable message, indicating that the destination port is unreachable and the IPv6 tracert ends. In this manner, the result of each probe is displayed on the source, according to which you can find the path from the source to the destination.

Configuration Impact

If a fault occurs when you run the tracert ipv6 command, the following information may be displayed:

!H: The host is unreachable.
!N: The network is unreachable.
!: The port is unreachable.
!P: The protocol type is incorrect.
!F: The packet is incorrectly fragmented.
!S: The source route is incorrect.

Precautions

By default, the ICMPv6 module is automatically enabled after you enable the IPv6 module.

Example

# Set the number of packets to be sent to 5 and timeout period to 8000 ms, and tracert the gateways from the source to the destination at FC00::3.

<HUAWEI> tracert ipv6 -q 5 -w 8000 FC00::3
traceroute to FC00::3 30 hops max,60 bytes packet
1 FC00:1::3 26 ms 23 ms 26 ms 30 ms 29 ms 
2 FC00::3 3020 ms 3024 ms 4040 ms 6820 ms 5584 ms

**Table 1** Description of the tracert ipv6 command output
Item	Description
traceroute to HH:HH::HH:H	IPv6 address of the destination host.
x hops max	Maximum hop-limit value.
x bytes packet	Length of a tracert packet.
1 2	Sequence number of the received ICMPv6 Echo Reply message.
HH:HH::HH:H	Address of the IPCMPv6 Echo Reply message.
26 ms 23 ms 26 ms 30 ms 29 ms	RTT, in milliseconds.