Cisco IOS Syslog Messages

Hi Lazaros,
Many thanks for your support.
but what about Logging console and No logging console command?
Is that command as the same as teminal monitor?

Hello again Mahmoud

Yes, you are correct, my explanation didn’t clarify this point.

Actually, terminal monitor displays system error messages AND debug command output. Conversely, logging console sends ONLY syslog messages to TTY lines, that is, console connections.

I hope this has been helpful.

Laz

Hi,
If I choose logging level 3 , means the log contains 3 and below ?
Thanks

Sims,
You are correct! When you choose a particular logging level, you are essentially choosing the LEAST severity you are interested in. Everything that is at the level you chose and more severe are included. In your example, you chose Level 3 (Error). This means you will get all of the following and nothing else:

Level 0 (Emergency)
Level 1 (Alert)
Level 2 (Critical)
Level 3 (Error)

Hi,
I want to know the difference between syslog and SNMP?

Hello Alb

Syslog is a standard that is used by many vendors for the purpose of message logging. Events that occur within a system (say a router or a switch) are categorised based on severity level as well as function and are stored in a buffer on the device itself or they are sent to a syslog server. These messages are used to for system management and security auditing as well as for general informational analysis and troubleshooting. Syslog messages are generated by the network devices themselves and are just read by the syslog server.

SNMP is a protocol that is used to collect and organise information about managed IP devices (such as routers and switches) but can also be used for modifying that information to change the device’s behaviour. SNMP differs from Syslog in many ways, but one of the most significant is that SNMP is more active in that an SNMP server can query and even modify specific variables (MIBs) that describe system status and configuration.

Although both are complementary in that they are both used for system monitoring and troubleshooting, their functionalities are quite different.

I hope this was helpful in getting you started off in further researching these useful technologies!

Laz

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With show logging history you can’t verify the setting of logging buffered severity. This can be done with show logging itself, show logging history shows the setting of logging history severity

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^ Indeed

It seems the “logging history” relates to the messages sent to an SNMP server. The buffered log (the one you were talking about in this lesson, sent to syslog server) is under “show log”

More info: https://www.cisco.com/c/en/us/td/docs/routers/access/wireless/software/guide/SysMsgLogging.html#wp1054946

Hello Philipp

Yes, you are correct. Based on the following Cisco command reference information, that is the case:


I will let @ReneMolenaar know to update the content.

Thanks again!

Laz

You guys are absolutely right, just fixed this.

Thanks!

Rene

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if you access via telnet or ssh and you do a “show log” and the logging buffered is configured until severity 4 (warnings) , the show log will only show up until warning messages despite the logging monitor was configured until severiry 6 (informational) ?

Hello Juan

You can set the severity that will be displayed/logged for each destination of a syslog message. For example, you can configure logging buffered level which will configure the severity level displayed when you do a show logging. The logging console level will configure the severity level that is displayed on the console. logging monitor level will configure the level that is displayed on vty lines, that is, on connections via SSH and Telnet. Finally, logging trap level will configure the level that will be sent to a syslog sever, if it has been configured.

So you can set the severity level of the syslog that is displayed for each destination of a syslog message.

I hope this has been helpful!

Laz

I am not sure if this is the right place to post my comment, but I like to give a try:

Is it possible to classify syslog so the command ‘snmp-server enable traps syslog’ can be skipped or modified? I do not like to send syslog informational/notificational to the snmp server, but wanted to send APPNAV/WAAS logs to the snmp server. But APPNAV/WAAS logs fall under the syslog, if we disable the command, then nothing will be sending to SNMP server.

Hi Sudip,

What syslog messages are you trying to forward for APPNAV/WAAS? I’d think that there should be an SNMP equivalant for this.

You could also create a simple EEM script that looks for your APPNAV/WAAS syslog messages, then forwards them to your SNMP server. This ensures that only these syslog messages get forwarded and nothing else.

Rene

To remember that various Levels of logging, Todd Lammle book says the following sentence
"Every Awesome Cisco Employee Will Need Icecream Daily " . This makes it easy to remember the levels from 0 to 7 with first letters of each word.

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Hi Rene,

my name is Juan nice to meet you, I want configure ( Adiscon LogAnalyzer), can you guide me for integrate with devices cisco this kind of syslog, please, I install Adiscon in Kali linux.

I do not know if it is enough to enable the website within / var / www / html in the root of kali linux, I create a testing environment and I have a switch with scope to this server syslog, configure the command "logging host 10.10 .64.150 “and” logging trap informational "but my server does not receive anything, I do not know if any database should be mounted to work in Kali, I am confused with this syslog that may be useful in the future.

Please I appreciate any support.

Hello Juan

It’s great that you are suggesting additional topics that can be added to the Networklessons site. It’s difficult to have each and every one responded to in full. I suggest you submit a new lesson idea at this page:


That way Rene can add new lessons and address the topics you mention in full.

I hope this has been helpful!

Laz

Hi Rene ,
Could you plz explain to me what does it null 0 in the routing table ?

Hello Allal

The Null0 route is used for various reasons in the routing table. Any routing entry that has an exit interface of Null0 will drop packets to that destination. Using Null0 you are explicitly stating that any packets destined to this specific destination will be dropped.

Null0 interfaces in the routing table are used for various reasons. One of the most common is when EIGRP summerization is enabled. EIGRP will advertise a summary route to other routers, but at the same time, will have a routing table entry to the summary route pointing to the Null0 interface. An example of such an entry in the routing table can be seen below:

R1#show ip route eigrp 
     172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
D       172.16.0.0/23 is a summary, 00:01:38, Null0

This is done to avoid routing loops. In the absence of any more specific route, the above routing table entry would cause any packets destined for this subnet to be explicitly dropped. More about this type of summarization (and why the Null0 interface is used) can be found in the following lesson:


I hope this has been helpful!

Laz

Thank you so much Lazaros :blush:

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