Tunnel Packet Direction Clarification

[salsamsisswe]

Need clarification.  In the display below, are packets input signifying traffic coming in"from" the other side of the tunnel, or packets that I am "sending" into the tunnel?

I have input counts but no output count. The tunnel is not up.  Am I not transmitting or am I not receiving according to below?

Show int tu0

5 minute input rate 125000 bits/sec, 187 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
68535093 packets input, 5756947860 bytes, 0 no buffer

0 packets output, 0 bytes, 0 underruns
Output 0 broadcasts (0 IP multicasts)
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops

[Joseph W. Doherty]

Input would be received, not sent.

[Giuseppe Larosa]

Hello @salsamsisswe ,

>> I have input counts but no output count. The tunnel is not up. Am I not transmitting or am I not receiving according to below?

if the local router considers the tunnel down it is not using it for sending traffic so input packets are packets coming from the remote site router that likely consider its side of the tunnel up.

You need to compare the configuration of the two tunnels to verify there is any difference.

A ping using source = tunnel source and destination = tunnel destination is successful or not ?

What about keepalive settings in the tunnel interface ?

A tunnel is just an abstraction that allows to encapsulate some traffic within an external IP header for this reason one side can be down and the other can be up at the same time, it depends on routing information about respective tunnel destination and what kind of checks are enabled or disabled ( the keepalive is the basic one)

Hope to help

Giuseppe

[Richard Burts]

I agree with the explanations that input is packets that you receive over the tunnel. If the tunnel shows as down then you are not transmitting. So the question becomes why is the tunnel down? I have some suggestions:

- can you clarify what type of tunnel this is? Is it simple GRE? Is it an IPSEC tunnel? Something else?

- can you check the logs on your device and see if there are any log messages about your tunnel? I am wondering about the possibility of recursive routing in which it is likely that your tunnel comes up and almost immediately goes down, flapping.

- is a ping successful if you specify the destination as the tunnel destination address and specify the ping source address as the tunnel source address?

- it might help us identify the issue if you would post the configuration of your device. (if you do not want to post the complete config then at least the tunnel configuration and the output of show ip route)