All right, so let's go ahead and log in into the lab
and actually configure weighted random early detect.
Now what we're gonna find is if we just enable
weighted random early detect,
it's actually going to base it on IP precedence, not DSCP.
And Cisco actually has a bunch of default values
in place for IP precedence,
because there's only eight different tags in IP precedence.
Well, when we enable DSCP based weighted random early detect,
which is what we should do in real life situations,
then we're gonna find that, well, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
then we're gonna find that, well,
Cisco's not going to put a bunch of defaults
for all of the different possible tags.
And so now it is more up to us to create those.
But interestingly, IP precedence values
can give us a decent template to work off of.
So let's go ahead and see this in action.
What we're gonna do here is we're just going to
do some example red configurations by creating,
first of all, a class map.
So we're gonna do that match any concept for,
we'll do AF2X here,
and I'm gonna say match DSCP and list out all of those. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and I'm gonna say match DSCP and list out all of those.
And from here, we're going to get onto that policy map test.
And now I'm gonna configure that class.
So class AF2X.
And now I can enable random detect.
Now, oh, yeah, let's get a bandwidth command in there.
So that is going to be required.
I'm just gonna say bandwidth 10,000
and now enable random detect.
So now what we can do is apply this to an interface. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So now what we can do is apply this to an interface.
So let's get on interface gig one zero
and do that service policy command to apply it
and we'll do it in the outbound direction.
And then remember that amazing command
show policy map interface
that we talked about in the last skill.
This is a really good command
for weighted random early detect as well.
So here's our class AF2X.
We see the traffic that's coming into, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We see the traffic that's coming into,
into and out of it, et cetera,
depending on the direction.
But right away we see what happened here.
We configured weighted random early detect,
but we configured it with just the default settings,
which means we actually have enabled it for IP presidents.
Not ideal in a real world situation,
but what this allows us to do is see
how exactly it's configured.
So we can see some statistics here, which is cool.
But over here we see that Cisco with a class IP president zero WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
But over here we see that Cisco with a class IP president zero
sets the minimum threshold to 20 and the maximum to 40.
All of these are set to a maximum of 40 you'll notice.
And then the mark probability is set to one out of 10.
Now again, it's not the mark probability denominator
because the denominator is itself 10.
And we'll see how we configure that here in a moment,
but when we configure the denominator to be 10,
that makes it so that the mark probability itself
is one out of 10 or 10%.
So this percentage is what we grow to.
So for class zero, starting at an average cube size of 20 WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So for class zero, starting at an average cube size of 20
packets, it's going to grow linearly all the way up
to a 10% drop probability before we start tail dropping
everything.
Now putting everything at 40 here is usually not
a great idea.
And so I wouldn't necessarily take these as Cisco recommendations,
but it's kind of interesting to see where they start to drop
packets.
And we do see that something as important as an IP
president of seven is going to start getting dropped at 34. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
president of seven is going to start getting dropped at 34.
So let's start to change this.
We're going to switch it over to DSCP.
I'm going to get back onto my policy map, get into that class AF2X.
Whoops, we've got to do DSCP.
Did I do that right?
Nope.
I didn't add the DSCP.
That's funny.
OK, so it is just AF2X.
Perfect.
So we're back onto this.
I'm going to say no random detect,
because I have to disable IP precedence based random detect. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
because I have to disable IP precedence based random detect.
And now I'm going to say random detect question mark.
And we're going to see that I can add this DSCP based concept.
Now, precedence based is an option here,
but it's the default option.
So this is why we need to specify DSCP based.
And now I can start to look at my red configurations,
w red configurations.
Now, again, what if I just take a moment to say show policy map
interface gig 1, 0? WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
interface gig 1, 0?
This is still applied to the interface.
So here's my AF2X class.
And notice we don't actually have any weighted random early
detect configuration in place for DSCP.
There is no defaults for DSCP.
So that's something to keep in mind there.
But fortunately, we can configure it ourselves.
So what we're going to do is we're going to say random detect.
And then DSCP, I'm going to specify my tag here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And then DSCP, I'm going to specify my tag here.
So I can specify whichever tag we're going to put in here.
This is the 2xq I'm going to start with 23.
This is my higher percent chance traffic of dropping.
So we probably want a little bit lower threshold to start with.
So again, I can set my minimum threshold in packet count.
Amazing how many packets we can put in a queue.
That's at least according to Cisco range there.
But I'm just going to say, out of 40, I'm going to say 28 here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
But I'm just going to say, out of 40, I'm going to say 28 here.
And then maybe a max range of 34.
And then this is where I set my mark probability denominator.
So again, I'm not saying 1 out of 10,
because that'd be the mark probability.
I'm just specifying the denominator of 10.
So now let's go back and look at that interface configuration.
And we see that we have AF23 with a minimum threshold of 28,
max of 34, mark probability of 110.
So now I can do something similar here. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So now I can do something similar here.
Random detect DSCP AF22.
Let's make it a little bit higher, not 28, but 30.
And not 34, but 36.
And we can set a mark probability of 25 here.
We don't have to use the same slope.
So now if I look at this, we'll see
we've got AF23 at the original one that we configured.
But now AF22 starts at 30 and to 36 and has a--
I said 25, 1 out of 25.
Yeah, I meant to say 1 out of 4, so that was 25%. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Yeah, I meant to say 1 out of 4, so that was 25%.
But keep that in mind.
Maybe we should practice this a little bit,
make sure we've got everything down.
All right, there we go.
So I wanted it to be 25%.
That would be a mark probability of 1/4.
And lastly, our AF21 traffic should be even higher.
So minimum threshold 32, maximum threshold 38.
And then we can say maybe when I actually
make it a much lower slope. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
make it a much lower slope.
So rather than 4 or 10, I could do something like 20.
So that's like a 5%.
1 and 20 is 5% at the most before it starts dropping fully.
And so there we go.
There's our configuration in place.
And say, well, why wouldn't we specify this at 40?
We could.
We could say at 40 would start dropping traffic.
Just keep in mind that there is potentially value in putting
it lower.
Usually we would just say 40. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Usually we would just say 40.
I'm not sure why I did 38 there.
Now let's just put it at 40.
There we go.
We really shouldn't drop the highest priority packets
until the queue is full.
But either way, we do see that this
is going to allow us to configure that weighted random early
detect in a way that takes a look at the different tags,
drops them in the proper order at the proper rates
that we very intentionally configure.
And we can confirm the configuration with that awesome WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And we can confirm the configuration with that awesome
command show policy map interface to see and make sure
that our configuration is correct.