vBRAS接口上有丢包该怎么排查

我发现都是下行丢包，上行不丢包，这个该怎么排查呢？

所有子接口都有相同的问题

Ten-GigabitEthernet5/0.4006

Current state: UP

Line protocol state: UP

Description: To-3#-E

Bandwidth: 10000000kbps

Maximum Transmit Unit: 1600

Internet Address is 172.18.48.1/22 Primary

IP Packet Frame Type:PKTFMT_ETHNT_2, Hardware Address: 7425-8ae3-b9d2

IPv6 Packet Frame Type:PKTFMT_ETHNT_2, Hardware Address: 7425-8ae3-b9d2

Output queue - Urgent queuing: Size/Length/Discards 0/100/0

Output queue - Protocol queuing: Size/Length/Discards 0/500/0

Output queue - FIFO queuing: Size/Length/Discards 0/75/0

Last clearing of counters: Never

Input: 27218237873 packets, 6262581347294 bytes, 0 drops

Output: 6078113055 packets, 6314427846233 bytes, 864747107 drops

Ten-GigabitEthernet5/0.4020

Current state: UP

Line protocol state: UP

Description: To-10#-E

Bandwidth: 10000000kbps

Maximum Transmit Unit: 1600

Internet Address is 172.19.16.1/22 Primary

IP Packet Frame Type:PKTFMT_ETHNT_2, Hardware Address: 7425-8ae3-b9d2

IPv6 Packet Frame Type:PKTFMT_ETHNT_2, Hardware Address: 7425-8ae3-b9d2

Output queue - Urgent queuing: Size/Length/Discards 0/100/0

Output queue - Protocol queuing: Size/Length/Discards 0/500/0

Output queue - FIFO queuing: Size/Length/Discards 0/75/0

Last clearing of counters: Never

Input: 0 packets, 0 bytes, 0 drops

Output: 1991 packets, 127424 bytes, 499 drops