I put a GRE tunnel over PPP link with ppp multilink fragmentation, the VoIP works fine but the data are slow with or without phone call´s
interface Multilink1
ip address x.x.x.x y.y.y.y
ip tcp header-compression iphc-format
service-policy output Quality
no cdp enable
ppp multilink
ppp multilink fragment-delay 20
ppp multilink interleave
multilink-group 1
ip rtp header-compression iphc-format
!
interface Serial0/0
bandwidth 128
no ip address
encapsulation ppp
load-interval 30
no fair-queue
ppp multilink
multilink-group 1
