[Virtual-pkg-base-maintainers] Bug#745587: base: Cloud AWS EC2 Image will not reply to packets received on additional network interface (ENI)

[Jeff Stiles]

Package: base
Severity: important

Dear Maintainer,

I recently ran into an issue with the AWS EC2 debian image found in the AWS Marketplace (ami-1ebcd32e). When                   
attaching a secondary Elastic Network Interface to the the instance during instance configuration and giving
it an IP address, there is strange network behaviour. First, the second network interface is not configured  
authomatically and you must manually add eth1 to /etc/network/interfaces. 

Upon restarting networking, the interface does acquire its IP address via DHCP from EC2. When sending traffic 
from eth1, you receive responses. However, when you initate traffic from another system in the same subnet 
as eth1, eth1 will not reply to the traffic (ICMP, SSH, etc).

The strangest part is that if you watch ifconfig for eth1, you will see the Rx incrementing from the traffic 
being sent to it, but with no corresponding Tx traffic. I can confirm that it is not a security group
issue as both network interfaces are in the same security group and subnet. 

I tried the newest Debian AMI and it has the same issue. The Ubuntu release in the AWS Marketplace also has
the same issue. When spinning up an Amazon Linux AMI, there is no issue. The secondary interface is configured
on first boot and there is not issue with traffic being handled properly by eth1.     

Here is a related bug for Ubuntu, but it does not address the issue of additional iterfaces not properly 
handling traffic:

https://bugs.launchpad.net/ubuntu/+source/cloud-init/+bug/1153626

Thanks,


-- System Information:
Debian Release: 7.4
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash