This is one of multiple IP version 6 troubleshooting videos in this network.
We've been told that a write of one on the left cannot ping the looped back of a rudder three the rudder
on the right so let's verify that now because this is IP version 6 of rather than IP version 4 notice
no IP version 4 rights exist in the writing table.
We need to do all our testing using IP version 6 something like paying the loop back of rudder 3 we
get a failure.
We are not able to ping the loop back of rudder 3.
Let's do a trace right and see how far we get okay.
So what do you think about to this output what's going on here.
Notice we're told that the destination was not found inside the max hop count diameter so let's do that
again.
Notice what's happening.
So where is the traffic going.
Now this is a good example of a rotting loop.
So if we scroll up notice what's happening.
Traffic it goes to RADA too.
Then it goes to RADA one then two wrote it two then two brought a one back to wrote it to back to RADA
one and so forth and so on.
So we have a loop taking place here.
So let's have a look at the writing table show IP these six right rudder one has a default route to
2001 Column 1 Column column 2 which is rather 2.
Hence the traffic is being sent to RADA too but on rudder to show IP v 6 around can you see the problem
here.
Pause the video if you need to but see if you can find the problem OK so we have a static default route
to write a three That looks okay there's a static round to the loop back of rudder one that also looks
okay here's a static route to the loop back of rotors three but that looks wrong.
Notice where it's pointing it's saying to get to the Loop pack of Rider 3 we need to go via route of
1.
So that's definitely not right and it's kind of redundant because we have this default front in the
routing table.
So show run pipe include route we need to get rid of this route and either fix the next hop or simply
remove it and rely on the default draft here.
So Ken wrote a one paying
the loop backup Rider 3.
OK the pings are still failing let's do a trace to that address the packet gets sent to brought to you
but then goes nowhere else.
So it doesn't look like it gets any further based on that output.
So Ken wrote it to ping the loop back of wrought a three
yes it can.
So rather to keeping the loop back wrote a three but rather one containing the loop back of rather three
so on rather three letters to a debug and check if the traffic is actually getting two rather three
from rather one and we can see that it is so we can see that the pings are arriving at a rather three
but it looks like the reply is not getting back to broader one so rather three received an echo request
from 2001 Colin one color in column one which is right one destination is the loop back of rudder three
so that the echo is sent but it's not getting back again so let's turn off debugging and let's do a
debug HPV six packet now in the real world you need to be very careful doing this I'm going to send
a single packet and let's see what happens again be very careful doing this in the real world you'll
get a lot of output even in the small network if we don't turn off debugging we might get a lot of output
on the console so there's the debug I sent a single ping from right I want to write a three we've got
a destination lookup for that the rudder sees that as a local network connected to the loop back so
that looks good but notice here IP these six forward no right to destination 2001 Colin one Colin Colin
one source is the loop back of rudder three destination is the gigabit 00 interface of rudder one and
we're told that there's no valid dropped so it doesn't look like a router three knows how to get back
to rudder one so show IP these six right is there a raft in the routing table to get back to rudder
one.
And the answer is No.
We have this static raft which would allow rather three to ping the loop back of rudder one but it can't
paying two thousand and one.
So what we need to do is add a static front to 2001 column one colon colon zero slash 64 and send that
to rudder to now let's do the ping again.
Notice the pings succeeded
and without using the repeat command the pings now succeed so we can get to the loop back of rudder
three and we can get to the physical interface of rudder three so be careful with pings.
This applies to both IP version 4 and IP version 6.
Just because I can send traffic to you doesn't mean that you know how to send traffic back to me.
Both sides need rots in the writing table to enable two way communication.
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