Unknown Protocol Drops on CE Router WAN Interface

[arun.patro]

Team,

I saw few past posts on this, but couldn't find an exact match. So, I am posting here again. Appreciate any feedback on this.

Issue: Observed 'unknown protocol drops' on WAN interface connecting to AT&T WAN Circuit. Also, this counter increases at same time as Multicast counter. See below 'sh int gi0/0/0' output. Required counters underlined in below output.

Router#sh int gi0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
Hardware is ISR4451-X-4x1GE, address is 3473.2d4a.d100 (bia 3473.2d4a.d100)
Description: link to PE; Location: RESTON, VA; Circuit ID: IZEC.544720..ATI
MTU 1500 bytes, BW 400000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 34/255, rxload 16/255
Encapsulation 802.1Q Virtual LAN, Vlan ID 1., loopback not set
Keepalive not supported
Full Duplex, 1000Mbps, link type is auto, media type is LX
output flow-control is off, input flow-control is off
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 4d08h
Input queue: 0/375/0/0 (size/max/drops/flushes); Total output drops: 1
Queueing strategy: Class-based queueing
Output queue: 0/40 (size/max)
5 minute input rate 26038000 bits/sec, 14825 packets/sec
5 minute output rate 53348000 bits/sec, 24418 packets/sec
1623435152 packets input, 358169497147 bytes, 0 no buffer
Received 0 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 12543 multicast, 0 pause input
2642593378 packets output, 840628799127 bytes, 0 underruns
Output 0 broadcasts (0 IP multicasts)
0 output errors, 0 collisions, 0 interface resets
12543 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

Router interface config as below:

Router#sh run int gi0/0/0
Building configuration...

Current configuration : 165 bytes
!
interface GigabitEthernet0/0/0
description link to PE
bandwidth 400000
no ip address
negotiation auto
end

Router#sh run int Gi0/0/0.3
Building configuration...

Current configuration : 445 bytes
!
interface GigabitEthernet0/0/0.3
description CE to PE -
bandwidth 400000
encapsulation dot1Q 3
ip flow monitor GLSFlowMonitor1 input
ip flow monitor GLSFlowMonitor1 output
ip address 10.64.16.165 255.255.255.252
no ip redirects
no ip unreachables
no ip proxy-arp
no cdp enable
bfd interval 999 min_rx 999 multiplier 3
no bfd echo
service-policy output MNS_COS_SHAPING_70-15-30-40-10-5
end

Router#

Let me know if any additional details required to check further. Thank you.

[balaji.bandi]

clear the counters, try no negotiation on the interface and check.

[Giuseppe Larosa]

Hello @arun.patro ,

I have seen this in the past with the other side router sending IS-IS hello packets that are non IP based but they are multicast.

So this can be a possible explanation the PE side is running an IS-IS process on its interface.

This has no real impact on your communication given the high difference between rx input packets and the unknown packet drops

Hope to help

Giuseppe

[arun.patro]

Thanks for the input. Here I check the PE side interface config. Is there anything else I should look at?

PE#sh run int TenGigE0/5/0/0.121
interface TenGigE0/5/0/0.121
description
bandwidth 400000
service-policy input V6_Ex_400M_70:15M:30M:40M:10:5M_in_sub shared-policy-instance 1
service-policy output V6_Ex_400M_70:15N:30W:40W:10:5W_out_sub shared-policy-instance 1
vrf 13979:452212
ipv4 mtu 1500
ipv4 address 10.64.16.166 255.255.255.252
dot1q vlan 70 3
!

PE#sh run int TenGigE0/5/0/0
interface TenGigE0/5/0/0
description
mtu 9122
carrier-delay up 2000 down 2000
load-interval 30
!