Hi there,
Im investigating a performance issue across a very convuluted network path, and Im not sure whether this issue is related to my performance issues or just a red herring.
I have a GRE tunnel, and I would expect the 'bytes output' on the source interface to equal the 'bytes input' on the destination interface, however they dont quite match.
See sh int tun0 outputs below.
RTR A.
Tunnel0 is up, line protocol is up
Hardware is Tunnel
Description: ;Tunnel to XXXXXX tunnel0
Internet address is a.a.a.a/30
MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL, loopback not set
Keepalive not set
Tunnel source b.b.b.b (Loopback0), destination c.c.c.c
Tunnel protocol/transport GRE/IP, key disabled, sequencing disabled
Checksumming of packets disabled, fast tunneling enabled
Last input 4d20h, output 01:18:23, output hang never
Last clearing of "show interface" counters 00:38:43
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 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
26 packets input, 2589 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
35 packets output, 3247 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
RTR B
Tunnel0 is up, line protocol is up
Hardware is Tunnel
Description: ;Tunnel to tunnel 0
Internet address is n.n.n.n/30
MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL, loopback not set
Keepalive not set
Tunnel source c.c.c.c (Loopback0), destination b.b.b.b
Tunnel protocol/transport GRE/IP, key disabled, sequencing disabled
Checksumming of packets disabled, fast tunneling enabled
Last input 00:12:12, output 00:12:17, output hang never
Last clearing of "show interface" counters 00:38:47
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 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
35 packets input, 3391 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
26 packets output, 2589 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
As you can see, the output bytes on RTR A does not match the input bytes of RTR B.
The MTU size isnt an issue (at least I dont think it is) as the traffic which is traversing the tunnel is max size 150 bytes, so the max MTU size isn't being reached. No fragmentation is occuring or else the no. of packets would be different. Any ideas or advice most welcome.
thanks
Joe
