Hello Community,
I am using ASR-901s to transport T1 traffic across a PSN. I am seeing increasing Egress drops on the cem circuit. The interface is showing no drops or loss of packets.
1. What does an Egress Drop mean? Does that mean there are drops before the UDP packets leave the ASR-901?
2. What is likely causing the drops?
Example 1
ASR-901 routers A and X. Neither router has anything attached to their T1 interfaces.
RouterA#sh cem cir 0
Load for five secs: 2%/0%; one minute: 2%; five minutes: 1%
Time source is NTP, 11:40:03.675 CDT Wed Aug 7 2019
CEM0/0, ID: 0, Line: UP, Admin: UP, Ckt: ACTIVE
Controller state: down, T1/E1 state: down
Idle Pattern: 0x55, Idle CAS: 0x8
Dejitter: 100 (In use: 0)
Payload Size: 192
Framing: Unframed
CEM Defects Set
Remote Packet Loss Packet Loss
Signalling: No CAS
RTP: No RTP
Ingress Pkts: 578002713 Dropped: 0
Egress Pkts: 0 Dropped: 577974850
CEM Counter Details
Input Errors: 0 Output Errors: 577974561
Pkts Missing: 30 Pkts Reordered: 41
Misorder Drops: 259 JitterBuf Underrun: 0
Error Sec: 0 Severly Errored Sec: 0
Unavailable Sec: 0 Failure Counts: 0
Pkts Malformed: 0 JitterBuf Overrun: 0
RouterA#sh int cem0/0
Load for five secs: 1%/0%; one minute: 1%; five minutes: 1%
Time source is NTP, 11:42:16.220 CDT Wed Aug 7 2019
CEM0/0 is up, line protocol is up
Hardware is Circuit Emulation Interface
Description: T1 from DACS to DACS
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 0 usec,
reliability 255/255, txload 255/255, rxload 254/255
Encapsulation CEM, loopback not set
Keepalive not supported
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 1543000 bits/sec, 1005 packets/sec
5 minute output rate 1544000 bits/sec, 1005 packets/sec
578138415 packets input, 111002575680 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 abort
578110265 packets output, 110997170880 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
RouterX#sh cem cir 11
Load for five secs: 1%/0%; one minute: 2%; five minutes: 2%
Time source is NTP, 11:57:58.071 CDT Wed Aug 7 2019
CEM0/11, ID: 11, Line: UP, Admin: UP, Ckt: ACTIVE
Controller state: up, T1/E1 state: up
Idle Pattern: 0x55, Idle CAS: 0x8
Dejitter: 100 (In use: 0)
Payload Size: 192
Framing: Unframed
CEM Defects Set
Remote Packet Loss Packet Loss
Signalling: No CAS
RTP: No RTP
Ingress Pkts: 2336024047 Dropped: 0
Egress Pkts: 0 Dropped: 1794377971
CEM Counter Details
Input Errors: 0 Output Errors: 0
Pkts Missing: 0 Pkts Reordered: 0
Misorder Drops: 0 JitterBuf Underrun: 0
Error Sec: 0 Severly Errored Sec: 0
Unavailable Sec: 0 Failure Counts: 0
Pkts Malformed: 0 JitterBuf Overrun: 0
RouterX#sh int cem0/11
Load for five secs: 3%/0%; one minute: 2%; five minutes: 2%
Time source is NTP, 12:01:31.721 CDT Wed Aug 7 2019
CEM0/11 is up, line protocol is up
Hardware is Circuit Emulation Interface
Description: DACS to DACS
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 0 usec,
reliability 255/255, txload 1/255, rxload 254/255
Encapsulation CEM, loopback not set
Keepalive not supported
Last input never, output never, output hang never
Last clearing of "show interface" counters 3w5d
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
5 minute input rate 1543000 bits/sec, 1005 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
2336235142 packets input, 448557147264 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 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
Example 2
Router B and Router X are exchanging live traffic. While the Egress Drops are less and less frequent they are still occurring. Router X in both examples are the same ASR-901.
RouterB#sh cem cir 0
Load for five secs: 2%/0%; one minute: 2%; five minutes: 2%
Time source is NTP, 12:08:09.810 CDT Wed Aug 7 2019
CEM0/0, ID: 0, Line: UP, Admin: UP, Ckt: ACTIVE
Controller state: up, T1/E1 state: up
Idle Pattern: 0x55, Idle CAS: 0x8
Dejitter: 100 (In use: 0)
Payload Size: 192
Framing: Unframed
CEM Defects Set
None
Signalling: No CAS
RTP: No RTP
Ingress Pkts: 575701115 Dropped: 0
Egress Pkts: 575688051 Dropped: 718
CEM Counter Details
Input Errors: 0 Output Errors: 0
Pkts Missing: 710 Pkts Reordered: 683
Misorder Drops: 8 JitterBuf Underrun: 0
Error Sec: 0 Severly Errored Sec: 0
Unavailable Sec: 0 Failure Counts: 0
Pkts Malformed: 0 JitterBuf Overrun: 0
RouterX#sh cem cir 0
Load for five secs: 1%/0%; one minute: 2%; five minutes: 2%
Time source is NTP, 12:01:54.777 CDT Wed Aug 7 2019
CEM0/0, ID: 0, Line: UP, Admin: UP, Ckt: ACTIVE
Controller state: up, T1/E1 state: up
Idle Pattern: 0x55, Idle CAS: 0x8
Dejitter: 100 (In use: 0)
Payload Size: 192
Framing: Unframed
CEM Defects Set
None
Signalling: No CAS
RTP: No RTP
Ingress Pkts: 1116160722 Dropped: 0
Egress Pkts: 1115452531 Dropped: 32071
CEM Counter Details
Input Errors: 0 Output Errors: 0
Pkts Missing: 31013 Pkts Reordered: 25323
Misorder Drops: 1048 JitterBuf Underrun: 10
Error Sec: 0 Severly Errored Sec: 0
Unavailable Sec: 0 Failure Counts: 0
Pkts Malformed: 0 JitterBuf Overrun: 0
