Unpredictable behavior of network after upgrading from debia

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Unpredictable behavior of network after upgrading from debia

Postby jdixit » 2017-10-23 13:40

Hi All,

We have been facing concerns ever since we upgraded our OS from Debian 6 to Debian 8.

System: We are using Debian 6 and over that we user openvpn to create tunnels over public IPs through 3G/4G modems and also through WiFi Modems. The Debian is being used on a LIVE Image ( we are using squashfs functionality )

Issue: While we get constant openvpn tunnels established when we are using Debian 6, the same doesn't happen when we try to upgrade this OS to Debian 8.

Details: Debian 6 is End of Life now so we tried to upgrade the system to Debian 8 with all the latest packages. Post this upgrade we started getting below issues which have become a show stopper for us:

--> When the system comes up, the bond interface ( we have 2 Physical interfaces and we have defined a bond interface on them ) doesn't come up by its own. We have to manually restart the networking to bring this UP. Post restart, teh IP auto IP assignment is successful.

--> The openvpn tunnels do come up on multiple reboots but say 2 in 6 times or so. Its an erratic behavior which is completely uncertain. Sometimes the links get established without any issue while sometimes they dont get connected even on 5-6 restarts. Have tried to tune many config but all in vain

--> Above mentioned scenario is of L3 connectivity. We tried to connect using L2 witha direct cable and making one as Openvpn server and other as client, it works perfect.

--> When the issue is faced, we observe that there is no response packet recieved from Server towards the client.

Any help or information on this will be highly appreciated. Do Let me know, If any further info is required.


Regards,
Jitendra
dixit.jitendra28@gmail.com
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Re: Unpredictable behavior of network after upgrading from d

Postby debiman » 2017-10-24 15:16

this is not a problem description for a linux forum.

this is a problem description for some commercial customer service: "i described the problem, now you come and fix it".

and that's not how we work.

also, you should already be getting the first spam messages into your now public email account... :D
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Re: Unpredictable behavior of network after upgrading from d

Postby jdixit » 2017-10-25 10:57

Hi debiman,

Thanks for your response. Hope below would be the suitable problem description:
ISSUE:
I am using a LTE/4G Modem at client side while I have a static public IP at the server side.

The Modem gets the public IP from the operator each time without any issue.

Following are the two cases being faced:

Success: When the modem connects trough 4G/LTE network, my Operating system which is Debian 8.9 connects to internet without any issue. Also it is able to create tunnel towards the OpenVPN Server. The tunnels establishes and data starts flowing between the client and the server.

Failure: When the modem connects trough 4G/LTE network, my Operating system which is Debian 8.9 doesn’t connects to internet. In this case, While checking the details the request from client goes towards server ( interesting to note that this communication is going on between two public IPs ) and gets a response as well from it. The response also reaches the 4G/LTE Modem interface but even then the tunnel doesn’t establish. Below is a tcpdump of ping response during the Issue, Which indicates that Debian is receiving response of every request but its not reaching to application somehow.

IP Address of Modem: x.x.x.y
Default Gateway (for Internet) : x.x.x.x

11:41:13.400582 IP x.x.x.y > x.x.x.x: ICMP echo request, id 5649, seq 34, length 64
11:41:13.905744 IP x.x.x.x > x.x.x.y: ICMP echo reply, id 5649, seq 34, length 64
11:41:14.408598 IP x.x.x.y > x.x.x.x: ICMP echo request, id 5649, seq 35, length 64
11:41:14.905735 IP x.x.x.x > x.x.x.y: ICMP echo reply, id 5649, seq 35, length 64
11:41:15.416577 IP x.x.x.y > x.x.x.x: ICMP echo request, id 5649, seq 36, length 64
11:41:15.877764 IP x.x.x.x > x.x.x.y: ICMP echo reply, id 5649, seq 36, length 64
11:41:16.424580 IP x.x.x.y > x.x.x.x: ICMP echo request, id 5649, seq 37, length 64
11:41:16.883796 IP x.x.x.x > x.x.x.y: ICMP echo reply, id 5649, seq 37, length 64
---------
root@system:/home/user# ping x.x.x.x
PING x.x.x.x (x.x.x.x) 56(84) bytes of data.
^C
--- x.x.x.x ping statistics ---
14 packets transmitted, 0 received, 100% packet loss, time 270144ms
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