Command:

priority-list protocol

Mode:

Router(config)#

Syntax:

priority-list list-number protocol protocol-name {high | medium | normal | low} queue-keyword keyword-value

no priority-list list-number protocol [protocol-name {high | medium | normal | low} queue-keyword keyword-value]


Syntax Description:

list-number

Any number from 1 to 16 that identifies the priority list selected by the user.

protocol-name

Protocol type: aarp, apollo, appletalk, arp, bridge (transparent), clns, clns_es, clns_is, compressedtcp, cmns, decnet, decnet_node, decnet_router-l1, decnet_router-l2, dlsw, ip, ipx, pad, rsrb, stun, vines, xns, and x25.

high | medium | normal | low

Priority queue level.

queue-keyword keyword-value

Possible keywords are fragments, gt, list, lt, tcp, and udp.


Command Description:

To establish queueing priorities based upon the protocol type, use the priority-list protocol global configuration command. To remove a priority list entry assigned by protocol type, use the no form of this command followed by the appropriate list-number argument and the protocol keyword.

When you use multiple rules for a single protocol, remember that the system reads the priority settings in order of appearance. When classifying a packet, the system searches the list of rules specified by priority-list commands for a matching protocol type. When a match is found, the system assigns the packet to the appropriate queue. The system searches the list in the order it is specified, and the first matching rule terminates the search.

The decnet_router-l1 keyword refers to the multicast address for all level 1 routers, which are intra-area routers, and the decnet_router-l2 keyword refers to all level 2 routers, which are inter-area routers.

The dlsw, rsrb, and stun keywords refer only to direct encapsulation.

Use the tables to configure the queueing priorities for your system.

Table: Protocol Priority Queue Keywords and Values

Option Description

fragments

Assigns the priority level defined to fragmented IP packets (for use with the IP protocol only). More specifically, this command matches IP packets whose fragment offset field is nonzero. The initial fragment of a fragmented IP packet has a fragment offset of zero, so such packets are not matched by this command.


Note   Packets with a nonzero fragment offset do not contain TCP or UDP headers, so other instances of this command that use the tcp or udp keyword will always fail to match such packets.

 

gt byte-count

Specifies a greater-than count. The priority level assigned goes into effect when a packet size exceeds the value entered for the argument byte-count.


Note   The size of the packet must also include additional bytes because of MAC encapsulation on the outgoing interface.

 

list list-number

Assigns traffic priorities according to a specified list when used with AppleTalk, bridging, IP, IPX, VINES, or XNS. The argument list-number is the access list number as specified by the access-list global configuration command for the specified protocol-name. For example, if the protocol is AppleTalk, list-number should be a valid AppleTalk access list number.

lt byte-count

Specifies a less-than count. The priority level assigned goes into effect when a packet size is less than the value entered for the argument byte-count.


Note   The size of the packet must also include additional bytes because of MAC encapsulation on the outgoing interface.

 

tcp port

Assigns the priority level defined to TCP segments originating from or destined to a specified port (for use with the IP protocol only). 

udp port

Assigns the priority level defined to UDP packets originating from or destined to a specified port (for use with the IP protocol only). 

Table: Common TCP Services and Their Port Numbers

Service Port

FTP data

20

FTP

21

SMTP

25

Telnet

23

Table: Common UDP Services and Their Port Numbers

Service Port

DNS

53

NFS

2049

RPC

111

SNMP

161

TFTP

69



Example:

The following example assigns 1 as the arbitrary priority list number, specifies DECnet as the protocol type, and assigns a high-priority level to the DECnet packets transmitted on this interface:

Router(config)#priority-list 1 protocol decnet high

The following example assigns a medium-priority level to every DECnet packet with a size greater than 200 bytes:

Router(config)#priority-list 2 protocol decnet medium gt 200

 The following example assigns a medium-priority level to every DECnet packet with a size less than 200 bytes:

Router(config)#priority-list 4 protocol decnet medium lt 200

The following example assigns a high-priority level to traffic that matches IP access list 10:

Router(config)# priority-list 1 protocol ip high list 10

The following example assigns a medium-priority level to Telnet packets:

Router(config)# priority-list 4 protocol ip medium tcp 23

The following example assigns a medium-priority level to UDP Domain Name Service packets:

Router(config)#priority-list 4 protocol ip medium udp 53

The following example assigns a high-priority level to traffic that matches Ethernet type code access list 201:

Router(config)#priority-list 1 protocol bridge high list 201

The following example assigns a high-priority level to DLSw+ traffic with TCP encapsulation:

Router(config)#priority-list 1 protocol ip high tcp 2065

The following example assigns a high-priority level to DLSw+ traffic with direct encapsulation:

Router(config)#priority-list 1 protocol dlsw high

Note   These commands define a rule that determines how packets are attached to an interface. Once the rule is defined, the packet is actually attached to the interface using the priority-group command.


Misconceptions:

None

Related Commands:
None

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