Redirecting NSX firewall syslogs into SmartLog


So we know that NSX DFW is a cool toy, but its logs are invaluable for debugging and forensics. Wouldn’t it be cool if would could see DFW logs along with SmartLogs???So our need is to have single-pane of glass security; Enter vSec and SmartLog.

After 100 VMs we knew that using DFW would just not work. In addition the logging was painful syslog based. So we decided to use the best management and logging tools on the market….and it just so happens this is one of the things CP does extremely good. Management and logging. Today’s talk is on “Having Fun with Logging”.

So we needed to get the DFW syslogs into SmartLog. How to do that. Well, first thing you do is pour salt on the documentation.  Its OK, but only gives you the basics. I have decoded this documentation and will show you how to send DFW logs to SmartLog and make it go a lot faster. By default, you can just turn it on with factory defaults… but will overwhelm your SmartLog server and all the data will be in the ‘info’ field and not parsed out. So it took me a couple months to figure out how to do all the parsing efficiently so as not to bury our log server.

And now for the rest of the story…..



NSX is the part of vMWare vSpere that runs its SDN…including the firewalls..Distributed Fire Walls (DFW). These firewalls send their syslog to their eSXI hosts which we forward to a custom syslog-ng server on a single VM.  We customized this syslog-ng server to parse DFW logs into CSV format….no easy task but doable. Why????


Once in CSV, syslog-ng forwards the logs to ‘syslog’ on currently a UTM 4800 with 4 cores. This is a custom syslog built by CP to accept syslog and convert to CP native log format. ‘syslog’ forwards the converted logs to fwd which enables SmartLog and Tracker to read the logs.

Simple enough…….ok, then read no further.

syslog-ng config

Syslog-ng allows you to parse through logs and reformat them. You can do some simple parsing with the basic configuration file, but the fun starts with more complex patterns with the pattern matching databases. Basically you need to convert this:


into this:


Now all you people are tons smarter than this old balding has-been…so I am not going to explain syslog-ng internals to you all. You will have to read the documentation. But I will give you the overview of what I did with it.

syslog-ng has two parts

  • General filtering config – Most people use this just for simple filtering of logs
    and re-formatting of logs and redirecting logs to host files, DB’s, other log servers.
  • Pattern Database – More complex parsing where you can take pieces of the input line, parse out specific items with regex, and insert those regex patterns into variables/macros to be used later in the General Filtering Config.

General Filtering Config: First thing you need to do only filter on DFW logs and nothing else.  NSX puts labels on these logs and you will have to look in the raw log file for it.


Second thing you have to do is get rid of the TERM log entries (terminate connections for TCP, for UDP you’ll see zillions of these going to 5355 some sort of local subnet DNS resolution. Unfortunately in cloud world we have huge subnets so all the VMs are doing this local link DNS resolution). 75% of the DFW logs are TERM entries so can be ignored.

Pattern Database: Next part is a bit harder. You have to build a pattern database that will parse raw DFW log entries and match each field up to a named macro. For example below is a snippet of a DFW log entry matching pattern. You can see the ‘action’, ‘domain’, ‘protocol’ fields are 3 of many fields that would match a DFW log entry from above.


This can be a delicate task, but there is a tool to help debug … ‘pdbtool match ‘. You can type in a sample line and see if the your pattern database will match it:


General Filtering Config: Next, DFW labels ICMP protocol as ‘PROTO’. So I just translate into normal geek lingo ‘ICMP’.


General Filtering Config:Next is the fun part. We finally get to output CSV to the CP syslog server. Notice how the MACRO names like ‘size’ and ‘protocol’ are used to fill in the CSV?


General Filtering Config: And here is the ‘main’ section that drives all the above phases:


so restart you syslog-ng server:

/etc/init.d/syslog-ng restart

and off you go!

At this point you can ‘tcpdump -X -n s0 port 514’ to verify that in fact the logs are formatted correctly and heading over to CP land.

SYSLOG Testing

Just in the off case my code sucks, here is how you test it. There are syslog generators out there that you can use: I used this one and here you can see how I generated traffic:


One key thing is the “dfwpktlogs–” is what triggers the regex’s to fire in the next section. Do NOT use ‘:’, you have to use ‘–‘ or for some reason the regex won’t parse correctly. More below…



So now the logs are flowing to port 514 on SmartCenter Log server. So you have to make sure you enable the syslog process (NOT syslogd) to listen.



This will start the syslog process on port 514 on SmartCenter.


On a MLS, you have to restart the whole MLS for the config to kick in. On MLS, a syslog daemon will be started PER domain log server IP address for every domain SYSLOG is configured to accept SYSLOGs for that domain.


and syslogng logs will flow magically into Tracker. Actually they will magically flow, but only fill in the INFO field and will not parse …. yet.

Oh yeah, when debugging you can get the syslog process to re-read the syslog config with:

  1. mdsenv <DOMAIN>  # MDS only
  2. fw kill fwd; fwd -n &


OK, now it gets fun.

So there is this CP tool: Eventia Log Parser that looks pretty cool. You feed it your SYSLOGS and magic parsing configuration pops out the other end:



Yeaaaaaaah…NO. Doesn’t work and the config you output is so complex the SYSLOG engine will run at 100%. Both ELP and SYSLOG were written about the time after the Civil War and are on version 1.0…Typical CP V1 code so don’t get your hopes up. Let me know if you have better luck, I spent days on this.

So I decided to generate the syslog parsing config myself. I saw what ELP attempted and then came up with my own.

Remember that SYSLOG-NG is sending CSV formatted logs:


and CP SYSLOG is taking them in and turning them into SmartLog readable:


So let’s begin.

The debug process is this:

  1. mdsenv <DOMAIN> if on MDS
  2. Edit the syslog rules with your stuff
  3. ‘fw kill fwd; fwd -n &’ restarts the syslog daemon
  4. Use the syslog generator
    1. Forget all this parsing junk, just get the SYSLOG-NG to dump into the CP SYSLOG and see the results in TRACKER in the ‘info’ field
    2. Try and get the REGEX rule to fire on ‘dfwpktlogs–‘
    3. Try and get field #1 to parse and fill in some random text field for debugging
    4. Try and get field #1 to output into the official SmartTracker field
    5. Go to #2 for field #2/3/4/5….

So far I have given you enough information to do #4.1. Let’s work on #4.3.

This may look simple…but it took me days and days to fine tune this. The ELP generated config was pages and pages of REGEX expressions. I boiled down to 1 line:


Even if you aren’t a regex geek, you can see that I am parsing the CSV file into 9 fields.

REGEX GEEK OUT (don’t read this if you aren’t a regex geek):

FYI: They don’t implement FULL regex matching! Example: You can only have 9 matching field patterns, I couldn’t get it to recognize ‘:’, you can’t use lazy searches ‘.+?’. It is some limited hack that you will never figure out because there is no documentation other than examples.  AND their regex performance is horrible, so I tried to avoid using ‘.*’ because it is greedy and will scan the whole line and then backtrack. Instead I used the ‘[^,]’ which searches for all characters NOT ‘,’, which is the same as ‘(.*),’…but doesn’t have the backtracking.


============= END GEEK OUT===============================

So what is important is the ‘dfwpktlogs–‘.  When the regex sees this pattern, it will fill in the 9 columns of information from the CSV formatted input line. Now there are 3 different types of actions that will be taken depending on the results of a REGEX match:


  • NO MATCH on regex: Result->log entry with data in INFO field
  • MATCH: but no log entry, you matched the  ‘dfwpktlogs–‘ but trying to print out a number into Tracker or Data type error, wrong field name, syntax error on field names, etc.
  • MATCH and () field hits: can use index_value(1) to fill out fields (coming next)

OK so next you will try and parse field #1 which is the first ‘([^,]+)’. This is the PASS|DROP field from the CSV. What I did is I first captured the field and then dumped it into a random text field. This told me that 1) I captured it correctly 2) I am able to write to SmartTracker.


Here is the add_field that does this. add_field adds the field to tracker. Field_name is the Tracker field this case it is the ‘rule_name field” field_index is CSV field 1 (from 1-9). Field type is the type of the Tracker field. But beware, I didn’t always get this right and the log entries would just dissappear so I had to experiment. I also looked into:

$FWDIR/conf/syslog/CPdefined/*.C files for examples to see what their field types are.

You can also look into


to see the Tracker field names and types. Its a bit kludgey but between CPDefined examples and this file you’ll get close.

Here you can see ‘rule_name” is the name of the Tracker field defined in svt_fields.C.



So now you have 1) You captured field #1 and 2) You wrote it to ‘rule_name’ field. You can now verify that you captured the field you intended to. Once you verify this, you can then write it to the REAL field with:syslog-tracker-real-field

Here we are writing the PASS|DROP to the ‘action’ field in tracker:


HOLD ON DREEZ: How in the heck did PASS|DROP get converted to Accept|Drop???? you ask.

Grasshopper, I introduce the dictionary file…


This is a second file in the same directory that will do transforms for you. Here you can see “PASS” being converted to ‘accept’.

DREEZ you ask: How do I know what to convert to what?

Oh yes grasshopper. You read the CP documentation…NOT!!! HAHAHAHAHAH. Dreez makes a big funny. HAHAHAHAH. Remember grasshopper, this documentation was written in the Civil War and even now the Lord Developers rarely talk to their lowly documentation peasants slaving in the fields trying to identify nuggets of information to feed their ignorant customers. (If you want real documentation see AWS documentation, you can see where developers talk to the documentation team). That’s what phone support is for —- DUH!!!!

Oh yes, I easily diverge, forgive me.

No grasshopper you do what us old people have been doing for centuries. You look at examples in



On your log server: fw log

Will print out your logs with the field names in them.

To get a feel of what the valid field types are.

So now that you know how to do field #1, now you go through all the fields one at a time….or……

You can just use my template as a starter!!!



So the first time we did this, we used CP’s syslog ELP generated config on one of our big servers and the server went to 100%++++. Unfortunately the ‘syslog’ process is single threaded so it had no where else to go.

So with 1100 VM’s….each with its own firewall…sending syslog to my config described above to a 4800 (slow) based management station…performance was much better but not ideal. The 4800 has a quad core Q9400 on it. Syslog process is a bit busy but at least not 100%. It will average between 11% and 60%, and burst to 90% now and then.

Now remember that on MLM, each domain/cma/clm has its own ‘syslog’, so you can manually distribute the load amongst multiple logging domains. But I would hate to do domain design based on log loads. For example, at one company 2 of 12 domains had 90% of our logging. So should we split them up further because of logging? Not sure.

Your mileage may very….



Everyone is excited about this because SmartLog is what our org (and all the other orgs I’ve been at) live and die by. Centralized single-pane of glass easy to use and fairly fast security monitoring. It is the gem of all of CP’s products. And it mostly sometimes works!!!

Now we can send logs from other tools like other firewalls, URL filtering, FireEye, etc into this and use SmartLog to get quick answers. I am keeping both flat syslog files as well as sending them to mongodb and SmartLog. YES: SEIM tools exist…but either they don’t work, too expensive or at capacity, etc. ‘grep’ is free. ‘mongodb’ is free, etc.







Post a comment or leave a trackback: Trackback URL.


  • John Fleming  On May 10, 2016 at 3:51 pm

    This is really an amazing write up. Thanks so much for sharing what you find.

  • vistor  On April 16, 2020 at 10:40 am

    THANKS alot for this!

    Just to add something 4 years later:
    – This works for NSX-T 2.5.1 aswell but need one thing for parsing.

    You can’t start your pattern with “INET” because NSX-T sends a process-ID/message-ID aswell. Instead do something like this in the dwf-patterfile: @STRING:processid:@

    INET match @STRING:action:@ @ESTRING:domain: @@STRING:direction:@ @NUMBER:size:@ @STRING:protocol:@ @NUMBER:size:@ @IPv4:srcip:@@ESTRING:arrowjunk:>@@IPv4:dstip:@

    @STRING:processid:@ INET match @STRING:action:@ @ESTRING:domain: @@STRING:direction:@ @NUMBER:size:@ @STRING:protocol:@ @NUMBER:size:@ @IPv4:srcip:@@ESTRING:arrowjunk:>@@IPv4:dstip:@

    • Dreezman  On April 16, 2020 at 10:59 pm

      Wow…did not know people were still using this. Very cool, thanks for adding!!!

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These are stories from my travels. Generally I like to write stories about local people that I meet and also brag about living the retirement dream with my #1 wife Gaby. She is also my only wife.

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