Solved: Serial port connected to a VSAT modem (ComTech) not pinging itself

Menezor · ‎07-25-2023

The

serial 0/1/1

is not pinging itself locally or passing traffic and all config seems to be good. connected to Comtech Modem 571

below are the interface details and IP rout

R1#sh int se0/1/1
Serial0/1/1 is up, line protocol is up
Hardware is WIC MBRD Serial
Description: VSAT 
Internet address is 10.80.255.41/30
MTU 1500 bytes, BW 256 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation HDLC, loopback not set
Keepalive set (10 sec)
Last input 00:00:04, output 00:00:02, 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: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/1/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 192 kilobits/sec
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
88853 packets input, 9132246 bytes, 0 no buffer
Received 51048 broadcasts (0 IP multicasts)
190440 runts, 0 giants, 0 throttles
436664 input errors, 24197 CRC, 0 frame, 0 overrun, 0 ignored, 222027 abort
60962 packets output, 4688901 bytes, 0 underruns
0 output errors, 0 collisions, 2612 interface resets
1 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
35280 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up










R1#sh ip rout
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override

Gateway of last resort is not set

10.0.0.0/8 is variably subnetted, 8 subnets, 4 masks
C 10.80.48.0/23 is directly connected, GigabitEthernet0/1
L 10.80.48.40/32 is directly connected, GigabitEthernet0/1
C 10.80.52.0/25 is directly connected, GigabitEthernet0/2.10
L 10.80.52.1/32 is directly connected, GigabitEthernet0/2.10
C 10.80.52.128/25 is directly connected, GigabitEthernet0/2.20
L 10.80.52.129/32 is directly connected, GigabitEthernet0/2.20
C 10.80.255.40/30 is directly connected, Serial0/1/1
L 10.80.255.41/32 is directly connected, Serial0/1/1

Giuseppe Larosa · ‎07-27-2023

Hello @Menezor ,

from the show interface

ser0/1/1

output we see a lot of input errors that are much more then received packets:

>> 88853 packets input, 9132246 bytes, 0 no buffer
Received 51048 broadcasts (0 IP multicasts)
190440 runts, 0 giants, 0 throttles
436664 input errors, 24197 CRC, 0 frame, 0 overrun, 0 ignored, 222027 abort
60962 packets output, 4688901 bytes, 0 underruns
0 output errors, 0 collisions, 2612 interface resets

Serial interfaces try to ping themselves by sending the packet to the other side , but the link is not healthy so this is why it is not able to ping itself.

Check the cabling between the router and the VSAT modem

Hope to help

Giuseppe

View solution in original post

Giuseppe Larosa · ‎07-27-2023