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F5 – RST or ICMP Packet Rate
You can follow SOL13151 in order to increase the packets/sec value. However, I would caution against doing it or at least recommend keeping the value smaller. The default setting is in place to prevent the F5 from overwhelming its resources by sending out RST. This could potentially end up being a self-inflicted DoS. So, either don’t change […]
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GTM Code Upgrade
These are a few quick checks as part of the GTM code upgrade maintenance that will be useful. As part of the maintenance preparatory work, check the license “service check date” as per K7727 Before starting the code upgrade and after the code upgrade, the following can be utilized to check the status of the […]
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Network Troubleshooting Tools
This is a short list of commonly available network troubleshooting tools that has been of use to me: Ping. traceroute. nslookup/dig curl. Error logs on the device. tcpdump. Developer tools within a browser like Chrome/FF. Wireshark.
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Clear SSH Key File
A simple way to clear the contents of ssh key file without deleting the file: echo -n > /home/user/.ssh/known_hosts
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Basic VTP
VTP stands for VLAN Trunk Protocol. VTP is used to propagate VLAN cconfiguration. VTP advertisements are multicasted. They are sent every 5 minutes or whenever there is a change in VLAN configuration. VTP revision number is included in these advertisements. Whenever a client receives a VTP advertisement with a higher revision number, the client will […]
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Basic DHCP Configuration
This is a simple DHCP configuration on a Layer 3 Switch: SW1(config)# ip dhcp excluded-address 10.10.10.1 SW1(config)# ip dhcp pool VLAN20POOL SW1(dhcp-config)# network 10.10.10.0 255.255.255.0 SW1(dhcp-config)# default-router 10.10.10.1 SW1(dhcp-config)# lease 2 Lease is in hours. Default-router IP indicates the default hop for the 10.10.10.0/24 network. The excluded-address will not be available to the DHCP client […]
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F5 GTM – DNS Query Processing Order
When a DNS query arrives at a F5 GTM/DNS, this is the processing order for the DNS query. 1 – DNS Query is processed by the Listener. 2- If Recursion Desired (RD) flag is set in the incoming query and if the DNS Profile associated with the Listener has “Process Recursion Desired” enabled, the following […]
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Ansible Playbook Optimizing
$ cat ansible.cfg [defaults] hostfile = ./hosts host_key_checking = False timeout = 5 log_path = ./logfile.txt forks = 50 gathering = smart [ssh_connection] pipelining = True The above file shows the content of ansible.cfg file. I have added the following to make my playbook run faster: forks gathering pipelining Forks indicate the number of parallel […]
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Ansible & Python 3
While using Ansible 2.2 and Python 3.x, I ran into the following error: ERROR! Unexpected Exception: No module named ‘urlparse’ Workaround: 1. Downgrade Python to 2.x 2. If there is no root level permission, use virtual env: virtualenv –python=python2.7