We believe that your issue has been closed by the upload of
Version 0.8.4 of grml-network from Michael Prokop <mika@grml.org>.
The explanation is attached below

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Hash: SHA256

Format: 1.8
Date: Tue, 23 Aug 2016 14:21:19 +0200
Source: grml-network
Binary: grml-network
Architecture: source all
Version: 0.8.4
Distribution: unstable
Urgency: medium
Maintainer: Michael Prokop <mika@grml.org>
Changed-By: Michael Prokop <mika@grml.org>
Description:
 grml-network - network related helper scripts
Changes:
 grml-network (0.8.4) unstable; urgency=medium
 .
   * [4fa68f7] netcardconfig: switch from `ifconfig` to `ip link` for
     interface parsing [Closes: issue2219] Thanks to Jakob Haufe
     <sur5r@sur5r.net> for the bugreport and patch
Checksums-Sha1:
 aef140fe7bd5399a4bfadf3e8105b6f1641ebc7e 1584 grml-network_0.8.4.dsc
 64a2cbd9b9a624d7f866630c1c873d30a84b42ac 23742 grml-network_0.8.4.tar.gz
 f1894ec519494274ffd8d9aad0e3d39da64d00ab 32506 grml-network_0.8.4_all.deb
Checksums-Sha256:
 44ee8e9944e4499bb853e0b904ab3eda0e82289ce22571541120957f35f2394f 1584 grml-network_0.8.4.dsc
 d0f5ef724ca44c43f2e34ff5e4d57535f1555ac5aff67102a72a65700e58295d 23742 grml-network_0.8.4.tar.gz
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Files:
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 9dab09fa8184315f2dab179db11cb7bb 23742 grml optional grml-network_0.8.4.tar.gz
 ee067829042ded4cdfd6a1d82134501b 32506 grml optional grml-network_0.8.4_all.deb

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ifconfig as of Debian stretch uses a different output format. This breaks
enumeration of devices in netcardconfig line 576.

Continuing to use ifconfig, the line should be changed to:

/sbin/ifconfig -a | awk ' !/^\s/{sub(/:/,"",$1);IFACE=$1} /Ethernet/{if (IFACE
!~ /^vmnet/) print IFACE" "$2}'

Unfortunately, this no longer works with ifconfig as of jessie.

Therefore, I suggest switching to ip(8):

ip link show | awk ' !/^\s/{sub(/:/,"",$2);IFACE=$2} /link.ether/{if (IFACE !~
/^vmnet/) print IFACE" "$2}'

This works on both jessie and stretch.