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NAME | SYNOPSIS | DESCRIPTION | COMMANDS | PARAMETERS | EXAMPLE & USAGE | EXIT STATUS | SEE ALSO | REPORTING BUGS | AUTHOR | COLOPHON |
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DCB-APP(8) Linux DCB-APP(8)
dcb-app - show / manipulate application priority table of the DCB
(Data Center Bridging) subsystem
dcb [ OPTIONS ] app { COMMAND | help }
dcb app { show | flush } dev DEV [ default-prio ] [ ethtype-
prio ] [ stream-port-prio ] [ dgram-port-prio ] [ port-
prio ] [ dscp-prio ] [ pcp-prio ]
dcb app { add | del | replace } dev DEV [ default-prio
PRIO-LIST ] [ ethtype-prio ET-MAP ] [ stream-port-prio
PORT-MAP ] [ dgram-port-prio PORT-MAP ] [ port-prio PORT-
MAP ] [ dscp-prio DSCP-MAP ] [ pcp-prio PCP-MAP ]
PRIO-LIST := [ PRIO-LIST ] PRIO
ET-MAP := [ ET-MAP ] ET-MAPPING
ET-MAPPING := ET:PRIO
PORT-MAP := [ PORT-MAP ] PORT-MAPPING
PORT-MAPPING := PORT:PRIO
DSCP-MAP := [ DSCP-MAP ] DSCP-MAPPING
DSCP-MAPPING := { DSCP | all }:PRIO
PCP-MAP := [ PCP-MAP ] PCP-MAPPING
PCP-MAPPING := PCP:PRIO
ET := { 0x600 .. 0xffff }
PORT := { 1 .. 65535 }
DSCP := { 0 .. 63 }
PCP := { 0(nd/de) .. 7(nd/de) }
PRIO := { 0 .. 7 }
dcb app is used to configure APP table, or application priority
table in the DCB (Data Center Bridging) subsystem. The APP table
is used to assign priority to traffic based on value in one of
several headers: EtherType, L4 destination port, or DSCP. It also
allows configuration of port-default priority that is chosen if no
other prioritization rule applies.
DCB APP entries are 3-tuples of selector, protocol ID, and
priority. Selector is an enumeration that picks one of the
prioritization namespaces. Currently it mostly corresponds to
configurable parameters described below. Protocol ID is a value in
the selector namespace. E.g. for EtherType selector, protocol IDs
are the individual EtherTypes, for DSCP they are individual code
points. The priority is the priority that should be assigned to
traffic that matches the selector and protocol ID.
The APP table is a set of DCB APP entries. The only requirement is
that duplicate entries are not added. Notably, it is valid to have
conflicting priority assignment for the same selector and protocol
ID. For example, the set of two APP entries (DSCP, 10, 1) and
(DSCP, 10, 2), where packets with DSCP of 10 should get priority
of both 1 and 2, form a well-defined APP table. The dcb app tool
allows low-level management of the app table by adding and
deleting individual APP 3-tuples through add and del commands. On
the other hand, the command replace does what one would typically
want in this situation--first adds the new configuration, and then
removes the obsolete one, so that only one prioritization is in
effect for a given selector and protocol ID.
show Display all entries with a given selector. When no selector
is given, shows all APP table entries categorized per
selector.
flush Remove all entries with a given selector. When no selector
is given, removes all APP table entries.
add
del Add and, respectively, remove individual APP 3-tuples to
and from the DCB APP table.
replace
Take the list of entries mentioned as parameter, and add
those that are not present in the APP table yet. Then
remove those entries, whose selector and protocol ID have
been mentioned as parameter, but not with the exact same
priority. This has the effect of, for the given selector
and protocol ID, causing that the table only contains the
priority (or priorities) given as parameter.
The following table shows parameters in a way that they would be
used with add, del and replace commands. For show and flush, the
parameter name is to be used as a simple keyword without further
arguments.
default-prio PRIO-LIST
The priority to be used for traffic the priority of which
is otherwise unspecified. The argument is a list of
individual priorities. Note that default-prio rules are
configured as triplets (EtherType, 0, PRIO). dcb app
translates these rules to the symbolic name default-prio
and back.
ethtype-prio ET-MAP
ET-MAP uses the array parameter syntax, see dcb(8) for
details. Keys are EtherType values. Values are priorities
to be assigned to traffic with the matching EtherType.
stream-port-prio PORT-MAP
dgram-port-prio PORT-MAP
port-prio PORT-MAP
PORT-MAP uses the array parameter syntax, see dcb(8) for
details. Keys are L4 destination port numbers that match
on, respectively, TCP and SCTP traffic, UDP and DCCP
traffic, and either of those. Values are priorities that
should be assigned to matching traffic.
dscp-prio DSCP-MAP
DSCP-MAP uses the array parameter syntax, see dcb(8) for
details. Keys are DSCP points, values are priorities
assigned to traffic with matching DSCP. DSCP points can be
written either directly as numeric values, or using
symbolic names specified in /etc/iproute2/rt_dsfield
(however note that the file specifies full 8-bit dsfield
values, whereas dcb app will only use the higher six bits).
dcb app show will similarly format DSCP values as symbolic
names if possible. The command line option -N turns the
show translation off.
pcp-prio PCP-MAP
PCP-MAP uses the array parameter syntax, see dcb(8) for
details. Keys are PCP/DEI. Values are priorities assigned
to traffic with matching PCP/DEI. PCP/DEI values are
written as a combination of numeric- and symbolic values,
to accommodate for both. PCP always in numerical form e.g 0
.. 7 and DEI in symbolic form e.g 'de' (drop-eligible),
indicating that the DEI bit is 1 or 'nd' (not-drop-
eligible), indicating that the DEI bit is 0. In
combination 2de:1 translates to a mapping of PCP=2 and
DEI=1 to priority 1.
Prioritize traffic with DSCP 0 to priority 0, 24 to 3 and 48 to 6:
# dcb app add dev eth0 dscp-prio 0:0 24:3 48:6
Add another rule to configure DSCP 24 to priority 2 and show the
result:
# dcb app add dev eth0 dscp-prio 24:2
# dcb app show dev eth0 dscp-prio
dscp-prio 0:0 CS3:2 CS3:3 CS6:6
# dcb -N app show dev eth0 dscp-prio
dscp-prio 0:0 24:2 24:3 48:6
Reconfigure the table so that the only rule for DSCP 24 is for
assignment of priority 4:
# dcb app replace dev eth0 dscp-prio 24:4
# dcb app -N show dev eth0 dscp-prio
dscp-prio 0:0 24:4 48:6
Flush all DSCP rules:
# dcb app flush dev eth0 dscp-prio
# dcb app show dev eth0 dscp-prio
(nothing)
Add a rule to map traffic with PCP 1 and DEI 0 to priority 1 and
PCP 2 and DEI 1 to priority 2:
# dcb app add dev eth0 pcp-prio 1nd:1 2de:2
# dcb app show dev eth0 pcp-prio
pcp-prio 1nd:1 2de:2
Exit status is 0 if command was successful or a positive integer
upon failure.
dcb(8)
Report any bugs to the Network Developers mailing list
<netdev@vger.kernel.org> where the development and maintenance is
primarily done. You do not have to be subscribed to the list to
send a message there.
Petr Machata <me@pmachata.org>
This page is part of the iproute2 (utilities for controlling
TCP/IP networking and traffic) project. Information about the
project can be found at
⟨http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2⟩.
If you have a bug report for this manual page, send it to
netdev@vger.kernel.org, shemminger@osdl.org. This page was
obtained from the project's upstream Git repository
⟨https://git.kernel.org/pub/scm/network/iproute2/iproute2.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-08.) If you discover
any rendering problems in this HTML version of the page, or you
believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a
mail to man-pages@man7.org
iproute2 6 December 2020 DCB-APP(8)
Pages that refer to this page: dcb(8), dcb-apptrust(8), dcb-rewr(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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