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Understanding Host Routing Engine Outbound Traffic Queues and Defaults

 

The host Routing Engine and CPU generate outbound traffic that is transmitted using different protocols. You cannot configure a classifier to map different types of outbound traffic that the host generates to forwarding classes (queues). The traffic that the host generates is assigned to forwarding classes by default as shown in Table 1.

If you want to separate host outbound traffic from other traffic or if you want to assign that traffic to a particular queue, you can configure a single forwarding class for all traffic that the host generates. If you configure a forwarding class for outbound host traffic, that forwarding class is used globally for all traffic generated by the host. (That is, the host outbound traffic is mapped to the selected queue on all egress interfaces.) Configuring a forwarding class for host outbound traffic does not affect transit or incoming traffic.

Whether you use the default host outbound traffic forwarding class configuration or configure a forwarding class for all host outbound traffic, the configuration applies to all Layer 2 and Layer 3 protocols and to all application-level traffic such as FTP and ping operations.

If you configure a queue for host outbound traffic, the queue must be properly configured on all interfaces.

Note

Fibre Channel over Ethernet (FCoE) Initialization Protocol (FIP) packets generated by the CPU are always transmitted on the fcoe queue (queue 3), even if you configure a queue for host outbound traffic. This helps to ensure lossless behavior for FCoE traffic. QFabric systems classify FIP control packets into the same traffic class (fcoe) across the Interconnect device (fabric) and the egress Node device.

This does not apply to OCX Series switches, which do not support FCoE.

By default, traffic generated by the host is sent to the best effort queue (queue 0) or to the network control queue (queue 7). Table 1 lists the default host traffic to output queue mapping.

Table 1: Routing Engine Protocol Default Queue Mapping

Routing Engine Protocol

Default Queue Mapping

Address Resolution Protocol (ARP) reply

Queue 0

ARP request

Queue 0

Border Gateway Protocol (BGP)

Queue 0

BGP TCP Retransmission

Queue 7

Fibre Channel over Ethernet (FCoE) Initialization Protocol (FIP)

Queue 3

File Transfer Protocol (FTP)

Queue 0

Internet Control Message Protocol (ICMP) reply

Queue 0

ICMP request

Queue 0

Internet Group Management Protocol (IGMP) query

Queue 7

IGMP report

Queue 0

Link Aggregation Control Protocol (LACP)

Queue 7

Open Shortest Path First (OSPF) hello

Queue 7

OSPF protocol data unit (PDU)

Queue 7

OSPF link state advertisements (LSAs)

Queue 7

Protocol Independent Multicast (PIM)

Queue 7

PIM hello

Queue 7

Simple Network Management Protocol (SNMP)

Queue 0

Secure Shell (SSH)

Queue 0

Telnet

Queue 0

Virtual Router Redundancy Protocol (VRRP)

Queue 7

VLAN Spanning Tree Protocol (VSTP)

Queue 7

xnm-clear-text

Queue 0

xnm-ssl

Queue 0