So here are my two routers, let's have a look at the logging levels, show logging on router 1, there's the
command, console
logging by default has enabled the level is debugging.
Other places where you can log are on the monitor.
That's typically when you telnet to a device buffer at the moment, the buffer logging is disabled.
Trap logging, which is used with the log server is set to the informational level, so notice console
is debugging level.
That's a level 7 trap logging is set by default on this router to informational, which is level
six.
So router 2 show logging
or show logging, rather.
Now, this router hasn't been changed
this is the defaults, so console is level 7, monitor is level 7 buffer is disabled and trap.
In other words, sending to syslog is set to informational.
So let's see what happens when we make some changes on the routers. I'll configure an IP address on each
router.
So, no, shut the interface.
Notice what happens when I type when the interface comes up.
In this case, the text is recopied
but on most routers by default, it will not be recopied. The reason it's done here is because, I'm
running this router within GNS3 and,
and by default on this GNS3 router, this command logging synchronoss was typed on the console.
So if I typed do show run
and have a look at the console
of this router.
What you'll notice is that logging Synchronoss has been enabled, which means when I'm typing a command,
I'm not interrupted and I'll just demonstrate that again, if I type interface loopback 0 and then
start typing the IP address.
Notice the command is retyped
on the console.
However, if I go into the console of this router and type no logging Synchronoss
and then type interface loopback 0 and start typing.
Notice my text is not recopied, it's stuck up there, so I need to press tab as an example to see what
I was typing.
So generally, you're going to want to type
logging Synchronoss on your console so that your text is recopied.
I'll enable OSPF on these routers
in area 0
just to make it simple.
I'll enable OSPF on all interfaces.
Just before I enable it on the other router, I'm going to enable OSPF adjacencies
and hit enter on the right hand side router.
Notice on the left hand side router, I'm getting a lot of output on the interface because I've enabled
debugging on router 2 I'm not getting any output because I haven't enabled debugging.
So on router 1 I'm seeing a lot of information, so show
IP OSPF neighbors an example shows me my neighbor relationship.
On router 2 I just got a level 5 notification saying that the neighbor relationship came up.
So level 5 is a notice, which is normal, but significant conditions, so I was informed that a
neighbor relationship came up but nothing else was displayed. Whereas on router 1 because I enabled
I was adjacency debugging.
I'm seeing a lot of output on the console of this router
and the reason it displays on the console is that I have a debugging level of logging on the console.
So when you enable debugging, you see the output.
Let's do the test again, so on the interface, I'll shut first Ethernet 00 on router 2.
So I see logging information that the adjacency went down, level 5 `interface went down level 5
message.
Line protocol has gone down level 5 message when I no shut the interface again
notice I see a lot of OSPF output on router 1
and once again, that's because I enabled debugging.
So if I type, show debug
you can see that OSPF adjacency debugging has been enabled and the level of logging is set at level
7.
If I, however, changed the logging on
the console
to level 3, level 3 is error conditions as an example. What would happen now
when I do the same test? So I've shut the interface on router 2
I'll no shut it.
On router 1 show debug
I'm still running the OSPF debugging, but notice I'm not seeing debug messages on the console.
Show IP OSPF Neighbor shows me that my neighbor relationship has come up and I can see that on router 2
which is still using
level 7 debugging on the console, but I don't see that on router 1 because I've changed the debbuging
to level 3,
in other words, errors.
I could once again change that to
level 7 and let's use a word, so debugging.
One last test,
shut the interface relationship is torn down, bring the interface up again
and notice, once again, I see the debugging on router 1 because I've changed to the logging level
to level 7.