2-2 
Figure 2-1 Traceroute process 
Device A
Hop Limit=1
Hop Limit exceeded
Hop Limit=2
Hop Limit exceeded
Hop Limit=n
UDP port unreachable
Device B Device C Device D
 
 
As 
Figure 2-1 shows, the traceroute process is as follows: 
z  The source sends an IP datagram with the Hop Limit of 1. 
z  If the first hop device receiving the datagram reads the Hop Limit of 1, it will discard the packet and 
return an ICMP timeout error message. Thus, the source can get the first device’s address in the 
route.  
z  The source sends a datagram with the Hop Limit of 2 and the second hop device returns an ICMP 
timeout error message. The source gets the second device’s address in the route. 
z  This process continues until the datagram reaches the destination host. As there is no application 
using the UDP port, the destination returns a “port unreachable” ICMP error message. 
z  The source receives the “port unreachable” ICMP error message and understands that the packet 
has reached the destination, and thus determines the route of the packet from source to 
destination. 
Table 2-2 Traceroute IPv6 
To do…  Use the command…  Remarks 
Traceroute IPv6 
tracert ipv6 [ -f first-ttl | -m max-ttl | -p 
port | -q packet-num | -w timeout ]* 
remote-system
 
Required 
Available in any view 
 
IPv6 TFTP 
IPv6 supports TFTP (Trivial File Transfer Protocol). As a client, the device can download files from or 
upload files to a TFTP server. For details about TFTP, see FTP-SFTP-TFTP. 
Configuration preparation 
Enable TFTP on the TFTP server and specify the path to download or upload files. For specific 
operations, refer to TFTP server configuration specifications. 
IPv6 TFTP configuration 
You can use the commands listed in Table 2-3 to download files from a TFTP server or upload files to a 
TFTP server.