AutoQoS Restrictions and Caveats
CEF must be enabled for AutoQoS to work. The interface must not have an
existing QoS policy configured. Bandwidth should be configured on each
interface. If you change the bandwidth after enabling AutoQoS, the router
does not change its QoS policies to reflect the new bandwidth. It classifies
links as slow or fast, with slow being 768 kbps or less. An IP address must
be configured on slow speed links prior to enabling AutoQoS because the
router uses Multilink PPP and transfers the IP address to the multilink interface
by default. On access switches, CDP must be enabled for the switch to
detect a Cisco IP phone.
SNMP support and an SNMP server address must be configured on the
router for SNMP traps to work. The SNMP string “AutoQoS” needs to have
write permissions.
AutoQoS supports the following WAN interfaces:
■ Frame Relay point-to-point subinterfaces. The PVC must not have a
map class or virtual template already assigned to it. If LFI is needed,
AutoQoS configures it for G.729 codec use. Manual tuning is needed
for G.711 use.
■ ATM point-to-point PVCs. The PVC must not have a virtual template
already assigned to it. Configure it as VBR-NRT.
■ Serial interfaces using PPP or HDLC. AutoQoS must be configured on
both sides of the link, and both sides must use the same bandwidth.