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[AUDIO LOGO]

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In this video, let's jump into
the command line on both iOS XR

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and iOS XE, and
we'll get an idea

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how route-refresh and
software configuration work

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on the two different platforms.

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We'll also take a
look at Wireshark,

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so we can see the
messages actually being

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sent between the two
routers on the wire.

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So let's jump in
and get started.

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We'll start on the command line
of router 1 looking at iOS XR.

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So since router 1
is running iOS XR,

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this will do route-refresh
automatically by default.

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So let's actually begin by
going into configuration mode

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into BGP, and let's do our
neighborship towards router 7.

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So that's 50.0.167.7.

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We'll go into our
address family for IPv4

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and let's configure
soft reconfiguration,

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and you can see here, it
only supports inbound.

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We haven't really mentioned
this before because there's not

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much to it.

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Doing an outbound
reconfiguration

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is actually quite simple.

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There's no special feature
or anything like that.

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We simply resend our local
BGP table to the neighbor

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through any new
outbound filters.

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So again, we haven't
really talked about it

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because there's honestly
nothing to talk about.

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The other router may not be
expecting an update from us,

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but it'll process
it if it comes in.

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So there's no notification or
any extra storing of tables

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or anything else
that needs to happen.

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For outbound, we just do it.

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So that's why the only
option here is inbound,

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and why we haven't
really discussed it.

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So let's go ahead
and do inbound.

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We'll commit those changes,
and we'll exit configuration.

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Now the first thing
we want to note

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is if we do a show BGP
neighbor for that 50.0.167.7

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and we do a received
routes, there's not

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going to be anything
shown, and it actually

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tells us right here that this
command is only available when

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inbound soft
reconfiguration is active.

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And it also tells
us that it's not

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going to be active if
the neighbor supports

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route-refresh.

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Now the cool thing is it does
tell us here how to fix it,

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but we're not going
to fix it just yet.

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We're going to
verify first that it

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is in fact using
route-refresh and ignoring

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the soft reconfiguration
that we just configured.

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Obviously, we can see that it
is, but let's take a look at it

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both in debug and in Wireshark.

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So first let's
turn on our debugs.

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So we'll start with a debug BGP
update for the address family

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IPv4 unicast, and
let's jump over

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and do a Wireshark capture.

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So here we've started a capture
on gigabit 3 of router 1,

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and we are filtering
it to be BGP but not

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if the BGP length is 19.

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That should specifically
keep out BGP

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keep alives just so we can
see the updates themselves.

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So now let's go do a
clear on our BGP session.

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So we'll say clear BGP
IPv4 towards that neighbor,

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and we'll do a soft inbound.

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So what we see here
is it's actually

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sending that refresh
request over to router 7,

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and then we see that we're
actually getting our updates

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as we requested them.

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So as we can see this did
not do soft reconfiguration,

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it's clearly a route refresh.

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We see the request go out, and
we see the updates coming in

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on our debug.

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Let's go see what
Wireshark showed us.

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So if we take a look
here at Wireshark,

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we can clearly see that
the first message sent here

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was from router 1 to
router 7, and it is in fact

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a route-refresh message.

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If we expand the
route refresh message,

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we can actually see here
that it was specifically

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for address family IPv4.

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And then if we look
back up at the top,

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we can see that our
second message coming in

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are the update messages
coming from router 7

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to router 1 actually
doing the route-refresh.

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So this was definitely a
route-refresh scenario.

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So let's go back
over to router 1

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and take a look at how we
get iOS XR to actually do

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the soft reconfiguration
inbound if the neighbor supports

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route-refresh.

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So before we go ahead
and fix it there's

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one more command we
can look at here,

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the show BGP neighbor detail.

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And if we scroll down a
bit, we can see right here

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under neighbor capabilities
that route-refresh

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is both advertised and received,
meaning both sides support

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route-refresh.

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So router 1 knows this.

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This is why router 1 is doing
the route refresh rather than

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the soft
reconfiguration inbound.

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So if we want it to
actually do that,

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we're going to have to force it.

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To do that, we'll go back
into configuration mode,

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back into the router,
back into the neighbor,

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back into the
address family, and

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after the soft
reconfiguration inbound,

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we're going to have
to turn on always.

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We'll commit those changes.

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Notice that since we still have
our debug on, as soon as we

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said commit, look what it did.

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If we scroll up just
a little bit here,

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we can see right here that it
sent a route-refresh request.

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So there's a little
bit of irony.

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It's doing a route-refresh to
populate the local table to do

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soft reconfiguration inbound.

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So there's nothing
wrong with this,

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it's just a little interesting
that it uses the newer

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method of doing a refresh, which
is the route-refresh request

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to populate the table
that we're going

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to be using for our soft
reconfiguration inbound.

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So let's see if that table
is actually populated now.

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So now let's look at
our received routes

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again, and notice that now we're
getting a prefix from router 7.

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So this is working properly.

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We now have this local copy.

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Also if we were to do a show IP
BGP for the prefix 108.8.8.0,

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notice here on the
entry from router 7,

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it's listing it as
both received and used.

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This means that it was received
through soft reconfiguration.

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It's being stored
locally, and it also

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happens to be, in this case,
the path that we're using.

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Also if we look at the details
of that neighborship now,

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notice that under
address family IPv4,

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next to the inbound software
configuration allowed,

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it actually says to
override route-refresh.

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So now that this is
supposedly working properly,

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let's verify it.

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So let's go ahead and do a soft
clear to that neighbor again.

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So the main thing
we want to see here

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is that it did not send
a route-refresh message.

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Now it's showing the replay
of the local table that's

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what these debugs
are, but there's

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no route-refresh
message being sent.

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In fact, we can see
right here that it's

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marking the neighbor for
soft reconfiguration.

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We could also see
this in Wireshark.

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Notice that we only have two
route-refresh messages here.

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The first one is the one
we looked at initially.

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The second one is
from when we enabled

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the soft
reconfiguration inbound.

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We saw that it did
a route refresh

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to get that information.

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But notice this third time
that we did the clear,

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there's no route-refresh
message for the third time

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we clear the neighborship.

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So we can see clearly this is
doing software reconfiguration

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now.

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So let's go back to router 1.

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First let's turn off
all of our debugging,

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and now let's look at this
same feature on iOS XE.

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So let's jump over
to router 7 next.

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So first on router 7, let's
look at its default behavior.

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So let's start with a
debug IP BGP update.

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Then we'll do an inbound
clear to our router neighbor.

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So although this one doesn't
actually say in the debug

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that it sent a
route-refresh request,

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we can see that as soon as
we hit Enter, all of a sudden

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we received all these
updates coming from router 1.

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So that's a pretty
good indicator

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that it was a route-refresh.

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We can also, of course,
see this in Wireshark.

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As we can see here
in Wireshark, we now

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have a third route-refresh
message in our output.

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And notice that this one is
coming from the source of .7

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going to the destination
of .1 So this is 7 asking 1

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for the route-refresh.

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So this is showing
that default behavior.

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Something else of interest
to note on iOS XE.

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If we come back over
here to router 7

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and instead we do a
soft in and hit Enter,

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we'll notice that it actually
does the exact same thing.

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There's no difference between
soft in and in on iOS XE.

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This is still doing
a route-refresh.

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If we look at Wireshark,
there's a second request

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now from router 7 to router
1, so this is clearly

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sending out refresh messages.

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The point is that both commands
do the same thing on iOS XE.

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Now let's turn on
soft configuration

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and see what changes.

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So first we'll go into
configuration mode.

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Router BGP 65001.

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For the neighbor, 50.0.167.1.

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We will do soft configuration.

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Just like iOS XR, inbound is,
of course, the only option.

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We'll end our configuration.

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And as we can see,
just like iOS XR,

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this already did
another route-refresh

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to populate the soft
reconfiguration inbound table.

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So this is doing the
exact same thing.

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Now if we do our
clear in again, notice

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how it's just doing a soft
reconfiguration inbound.

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It did not get all
those updates again,

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and it completed
in 2 milliseconds.

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The other update really didn't
tell us how long it took,

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so we don't really
have a comparison,

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but it was pretty quick.

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Also note that if we
again do the soft in,

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this is going to do
the exact same thing.

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So these two commands
in and soft in on iOS XE

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do exactly the same thing.

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The only real difference is
whether soft reconfiguration

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inbound is enabled or not.

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Just as a quick note in case
you're wondering why there's

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two different commands, on older
versions of the code going back

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quite a bit, in was
to do route-refresh,

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soft in was to do soft
reconfiguration inbound.

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And if you tried to do soft in
without enabling the feature,

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the router would yell at you
and say, no, you can't do that.

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You haven't enabled soft
reconfiguration inbound yet.

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Now it just looks and sees, oh,
well, route-refresh is enabled.

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That's good enough.

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So I see that you type
soft in, but we'll just

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do a route-refresh.

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So both commands on current
code do the same thing just

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based on whether soft
reconfiguration inbound is

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enabled, and of course,
assuming route-refresh

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was negotiated with the
neighbor during bring up.

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Just to completely verify,
let's go back here to Wireshark,

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and we can see
here that there was

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that last route-refresh message
sent to populate the software

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configuration table.

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But after that,
there are no more

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even though we did the
clear two more times.

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They're not here because they
were soft reconfiguration.

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And just like on iOS XR,
go back over to router 7.

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We can see that received
table here as well.

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If we do a show IP BGP
neighbor for the 50.0.167.1,

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we can do received routes.

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Here we can see the table that
we received from router 1.

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So we can see that this is
working exactly as we expected.

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In this video, we took a
look at how iOS XR and iOS

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XE behave in regard to
soft reconfiguration

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inbound versus route-refresh.

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We saw that both of them will
do route-refresh by default,

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but, of course, we can enable
the soft reconfiguration

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inbound.

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The interesting thing
to take away from this,

248
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though, is even if you enable
soft reconfiguration inbound

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on iOS XR, it actually won't
do it if the neighbor itself

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supports route-refresh, so
you have to actually force it

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00:14:11,970 --> 00:14:14,170
by saying always.

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I hope this has been
informative for you,

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and I'd like to thank
you for viewing.

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