Cisco IOL Nodes starts and stops for L2 image x86_64_crb_linux_l2-adventerprisek9-ms.bin

Make sure that License file is generated with python3

cd /opt/unetlab/addons/iol/bin
ls -l iourc
cat iourc
hostname
! need to check hostname of the server

The iourc file should look broadly like:

[license]
pnetlabs = your-valid-license-value;

The name before = must match the current PNETLab hostname exactly. If the server hostname was changed, restored, cloned or reinstalled, the existing licence may no longer match. PNETLab specifically identifies a corrupted iourc file as a common reason for IOL devices immediately stopping.

Also remove Windows line endings:

sed -i 's/\r$//' /opt/unetlab/addons/iol/bin/iourc
chmod 644 /opt/unetlab/addons/iol/bin/iourc
chown root:unl /opt/unetlab/addons/iol/bin/iourc

cd /opt/unetlab/addons/iol/bin

sed -i 's/\r$//' iourc
chown root:unl iourc
chmod 644 iourc

/opt/unetlab/wrappers/unl_wrapper -a fixpermissions

View file again

hostname
cat -A iourc

Expected:

pnetlab
[license]$
pnetlab = c833425160bc61ec;$

There must be no ^M at the end of either line.

/opt/unetlab/wrappers/unl_wrapper -a fixpermissions

Apply the specific L2 fix and check for the known xml.cisco.com issue

grep -n "xml.cisco.com" /etc/hosts
getent hosts xml.cisco.com

If it returns something such as:
127.0.0.1 xml.cisco.com

Remove that entry

sed -i '/xml.cisco.com/d' /etc/hosts

Then add the DNS-blocking rule:

iptables -I OUTPUT 1 -p udp --dport 53 \
-m string --hex-string "|03|xml|05|cisco|03|com" \
--algo bm -j DROP

Confirm the rule exists:

iptables -L OUTPUT -n -v --line-numbers | head -n 15

Clean the old sockets and fix permissions:

rm -rf /tmp/netio*
rm -rf /opt/unetlab/tmp/1/1/*
chmod 1777 /tmp

/opt/unetlab/wrappers/unl_wrapper -a fixpermissions

One important point: the iptables rule may disappear after a PNETLab reboot. Check whether persistent rules are installed:

dpkg -l | grep iptables-persistent

When available, save the working rule:

mkdir -p /etc/iptables
iptables-save > /etc/iptables/rules.v4