After config traffic ends in error-drop:

vppctl set interface state GigabitEthernet0/9/0 up
vppctl set interface ip address GigabitEthernet0/9/0 192.168.0.1/24
vppctl set interface state GigabitEthernet0/10/0 up
vppctl set interface ip address GigabitEthernet0/10/0 192.168.1.1/24
vppctl ip probe GigabitEthernet0/10/0 192.168.1.2
vppctl create gre tunnel src 192.168.1.1 dst 192.168.1.2
vppctl set interface state gre0 up
vppctl set interface ip address gre0 172.16.0.1/24
vppctl ip route add 11.0.0.0/24 via gre0

root@DUT-1:/home/lab# vppctl show interfaces
Name Idx State Counter Count
GigabitEthernet0/10/0 7 up rx packets 3
rx bytes 180
tx packets 3
tx bytes 126
drops 3
GigabitEthernet0/11/0 8 down
GigabitEthernet0/9/0 5 up rx packets 4
rx bytes 316
tx packets 2
tx bytes 102
drops 2
ip4 2
GigabitEthernet0/a/0 6 down
gre0 9 up tx-error 1
local0 0 down drops 1
pg/stream-0 1 down
pg/stream-1 2 down
pg/stream-2 3 down
pg/stream-3 4 down

root@DUT-1:/home/lab# vppctl show error
Count Node Reason
1 ip4-arp ARP requests sent
1 ip4-icmp-input echo replies sent
1 arp-input ARP replies sent
4 arp-input ARP replies received
1 gre0-output interface is down

root@DUT-1:/home/lab# vppctl show trace

Packet 6

00:00:35:914488: dpdk-input
GigabitEthernet0/9/0 rx queue 0
buffer 0x10eb9: current data 0, length 98, free-list 0, totlen-nifb 0, trace 0x5
PKT MBUF: port 0, nb_segs 1, pkt_len 98
buf_len 2176, data_len 98, ol_flags 0x0,
packet_type 0x0
IP4: 08:00:27:46:2b:4c -> 08:00:27:f3:be:f0
ICMP: 192.168.0.100 -> 11.0.0.1
tos 0x00, ttl 64, length 84, checksum 0x66c0
fragment id 0x07dc, flags DONT_FRAGMENT
ICMP echo_request checksum 0x933b
00:00:35:914519: ethernet-input
IP4: 08:00:27:46:2b:4c -> 08:00:27:f3:be:f0
00:00:35:914524: ip4-input
ICMP: 192.168.0.100 -> 11.0.0.1
tos 0x00, ttl 64, length 84, checksum 0x66c0
fragment id 0x07dc, flags DONT_FRAGMENT
ICMP echo_request checksum 0x933b
00:00:35:914529: ip4-rewrite-transit
fib 0 adj-idx 10 : gre0 flow hash: 0x00000000
GRE 0x0054
00:00:35:914532: gre0-output
gre0
GRE 0x0054
00:00:35:914539: error-drop
gre0-output: interface is down

root@DUT-1:/home/lab# vppctl show version
vpp v1.0.0-410~g27fe48f built by jenkins on ubnt-trusty-f29 at Fri Apr 29 14:37:50 UTC 2016
root@DUT-1:/home/lab#