Default Routing Engine Protocol Queue Assignments

Table 1 lists the default output queues to which Routing Engine sourced traffic is mapped by protocol type. In general, control protocol packets are sent over queue 3 and management traffic is sent over queue 0. The following caveats apply to these default queue assignments:

For all packets sent to queue 3 over a VLAN-tagged interface, the software sets the 802.1p bit to 110, except for VRRP packets, in which case the software sets the 802.1p bit to 111.
Outgoing BFD packets should be marked with VLAN-tagged 802.1p bit to 110; however, this is true only for RE based BFD. For inline BFD, it does not modify by default.
Although BGP and LDP TCP traffic is sent to queue 0, it is marked with 802.1p bits 110 normally used for network control.
For IPv4 and IPv6 packets, the software copies the IP type-of-service (ToS) value into the 802.1p field independently of which queue the packets are sent out.
For MPLS packets, the software copies the EXP bits into the 802.1p field.

Table 1: Default Queue Assignments for Packets Generated by the Routing Engine
Routing Engine Protocol	Default Queue Assignment
Adaptive Services PIC TCP tickle (keepalive packets for idle session generated with stateful firewall to probe idle TCP sessions)	Queue 0
Address Resolution Protocol (ARP)	Queue 0
ATM Operation, Administration, and Maintenance (OAM)	Queue 3
Bidirectional Forwarding Detection (BFD) Protocol	Queue 3
BGP	Queue 0
BGP TCP Retransmission	Queue 3
Cisco High-Level Data Link Control (HDLC)	Queue 3
Distance Vector Multicast Routing Protocol (DVMRP)	Queue 3
Ethernet Operation, Administration, and Maintenance (OAM)	Queue 3
Frame Relay Local Management Interface (LMI)	Queue 3
Frame Relay Asynchronization permanent virtual circuit (PVC)/data link connection identifier (DLCI) status messages	Queue 3
FTP	Queue 0
IS-IS Open Systems Interconnection (OSI)	Queue 3
Internet Control Message Protocol (ICMP)	Queue 0
Internet Group Management Protocol (IGMP) query	Queue 3
IGMP Report	Queue 0
Internet Key Exchange (IKE)	Queue 3
IP version 6 (IPv6) Neighbor Solicitation	Queue 3
IPv6 Neighbor Advertisement	Queue 3
IPv6 Router Advertisement	Queue 0
Label Distribution Protocol (LDP) User Datagram Protocol (UDP) hello	Queue 3
LDP keepalive and Session data	Queue 0
LDP TCP Retransmission	Queue 3
Link Aggregation Control Protocol (LACP)	Queue 3
Link Services (LS) PIC	If link fragmentation and interleaving (LFI) is enabled, all routing protocol packets larger than 128 bytes are transmitted from queue 0. This ensures that VoIP traffic is not affected. Fragmentation is supported on queue 0 only.
Multicast listener discovery (MLD)	Queue 0
Multicast Source Discovery Protocol (MSDP)	Queue 0
MSDP TCP Retransmission	Queue 3
Multilink Frame Relay Link Integrity Protocol (LIP)	Queue 3
NETCONF	Queue 0
NetFlow	Queue 0
OSPF protocol data unit (PDU)	Queue 3
Point-to-Point Protocol (PPP)	Queue 3
Protocol Independent Multicast (PIM)	Queue 3
Real-time performance monitoring (RPM) probe packets	Queue 3
RSVP	Queue 3
Routing Information Protocol (RIP)	Queue 3
SNMP	Queue 0
SSH	Queue 0
sFlow monitoring technology	Queue 0
Telnet	Queue 0
Two-Way Active Monitoring Protocol (TWAMP)	Queue 0
Virtual Router Redundancy Protocol (VRRP)	Queue 3
`xnm-clear-text`	Queue 0
`xnm-ssl`	Queue 0