Specifications

308 Implementing IBM System Networking 10Gb Ethernet Switches
Connecting via DATA port.
[host 10.0.100.1, max tries 5, delay 1000 msec , length 0]
10.0.100.1: #1 ok, RTT 0 msec.
10.0.100.1: #2 ok, RTT 0 msec.
10.0.100.1: #3 ok, RTT 1 msec.
10.0.100.1: #4 ok, RTT 0 msec.
10.0.100.1: #5 ok, RTT 0 msec.
You can see in the output that all five ICMP Echo requests received the replies. There is also
additional information about the Round Trip Time (RTT), that is, the time it took for the ACC-2
to receive the response from AGG-1. 0 msec means that the time was less than 1 ms.
Traceroute
You can use the traceroute command to not only verify connectivity to a remote network
node, but to track the responses from intermediate nodes as well. This action is done by
using the Time-To-Live (TTL) field in IP packets. The traceroute command sends a UDP
packet to a port that is likely to not be used on a remote node with a TTL of 1. After the packet
reaches the intermediate router, the TTL is decremented, and the ICMP time-exceeded
message is sent back to the originating node, which increments the TTL to 2, and the process
repeats. After the UDP packet reaches a destination host, an ICMP port-unreachable
message is sent back to the sender. This action provides the sender with information about
all intermediate routers on the way to the destination.
The command shown in Example 7-20 verifies which hops are on the way from the ACC-2
switch to AGG-1.
Example 7-20 Traceroute command example
ACC-2#traceroute 10.0.100.1 data-port
Connecting via DATA port.
[host 10.0.100.1, max-hops 32, delay 2048 msec]
1 10.0.100.1 0 ms
Trace host responded.
From the output, you see that there is only one hop on the way from ACC-2 to AGG-1, and it
is AGG-1 itself. We use OSPF in our network, which selects this path as the shortest one.
For test purposes, we shut down the direct links between ACC-2 and AGG-1 (ports 3 and 4)
and run traceroute again. The output is shown in Example 7-21.
Example 7-21 Traceroute command example
ACC-2#traceroute 10.0.100.1 data-port
Connecting via DATA port.
[host 10.0.100.1, max-hops 32, delay 2048 msec]
1 10.0.104.1 0 ms
2 10.0.100.1 1 ms
Trace host responded.
Now we can see that in order to get to AGG-1, ACC-2 uses the AGG-2 (10.0.104.1) switch
as the intermediate router.