vethx inteface support speed after bonding

hi, all

I have a DD6300, i have already configured veth0 - it's bonded two eth3a, eth3c - they connect over fiber cable to SW Cisco 4500, two ports 10gb uplink,

On Sw Cisco 4500 : port-chanel up, BW 20 Gb/s

But my veth0 only 10Gb/s

Interface Name:	veth0	Auto Negotiate:	Disabled
Hardware Address:	00:60:16:85:22:c8	Duplex:	Full
Cable:	Fiber	Speed:	10 Gb/s
MTU:	1500	Supported Speeds:	10000

Any problem with my config, everybody help me to solve it ?

Here is my configuration :

lv@dd6300-backup# net show settings

port    enabled   state     DHCP   IP address                   netmask          type   additional setting

                                                                /prefix length

-----   -------   -------   ----   --------------------------   --------------   ----   -------------------------------

ethMa   yes       running   no     10.36.202.15                 255.255.255.0    n/a

                                   fe80::260:16ff:fe86:c7c6**   /64

eth3a   yes       running   n/a    n/a                          n/a              n/a    bonded to veth0

eth3b   no        down      no     n/a                          n/a              n/a

eth3c   yes       running   n/a    n/a                          n/a              n/a    bonded to veth0

eth3d   no        down      no     n/a                          n/a              n/a

veth0   yes       running   no     10.36.202.16                 255.255.255.0    n/a    lacp hash xor-L2L3: eth3a,eth3c

                                   fe80::260:16ff:fe85:22c8**   /64

-----   -------   -------   ----   --------------------------   --------------   ----   -------------------------------

** auto_generated IPv6 address

Thanks !