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Barracuda NextGen Firewall X

How to use TOS-Bit values on Barraucda NG Firewall?

  • Type: Knowledgebase
  • Date changed: one year ago
Solution #00005206 
This solution replies to:
- NG Firewall firmware versions 4.2.x, 5.0.x, 5.2.x, 6.x, 7.x
- netfence firmware versions 4.2.x


What values must be inserted for TOS-Bit values?


TOS-Bit interpretation according to RFC3168 (since 2001) also known as the DSCP (DiffServ - may set as a value between 0 and 255. How this value will be interpreted is up to the remote site.


For example Cisco looks like this...

  Class AF11 - DSCP 10
  Class AF12 - DSCP 12
  Class AF13 - DSCP 14
  Class AF21 - DSCP 18
  Class AF22 - DSCP 20 
  Class AF23 - DSCP 22
  Class AF31 - DSCP 26
  Class AF32 - DSCP 28
  Class AF33 - DSCP 30
  Class AF41 - DSCP 34
  Class AF42 - DSCP 36
  Class AF43 - DSCP 38


More information about Cisco DSCP values are located here...


More information about precedence values are located here...



As a matter of principle the netfence controls the precedence field but you set set the DSCP value in the netfence configuration.


For example:
  DSCP       Precedence  Purpose 
  0            0            Best effort
  8            1            Class 1
  16           2            Class 2
  24           3            Class 3
  32           4            Class 4
  40           5            Express forwarding
  48           6            Control
  56           7            Control

Additional Note: In certain situations you might want to “clear” the TOS value of a received packet before it is forwarded out another interface. This is currently not possible. If you configure decimal value 0 within the access rule advance settings, that means the TOS value of the received packet stays unchanged.

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