Linux network namespaces - part 3

In this post program will be run with unshared network namespace.
Next connectivity from default network namespace will be configured towards unshared network namespace.

It is continuation of previous posts about Linux network namespaces:

• part 1
• part 2

Linux network namespaces - part 2

In this post two Linux network namespaces will be configured and communication will be set up between them using bridge interface.

It is continuation of the previous post about Linux network namespaces.

Linux network namespaces

Linux network namespaces provide isolation of system resources associated with networking.

When using kubernetes or containers in general, linux network namespaces are one of the building blocks of the solution.

Since I wanted to understand more about how things work behind the scenes when using containers, linux network namespaces were perfect to learn more about.

Kubernetes installation with Ansible

This post is about installing Kubernetes cluster with Ansible.

I wanted to learn about Kubernetes and have possibility to create lab/test clusters.

Git repository with Ansible playbooks and instructions which were prepared during that process can be found here.

FRR - installation and configuration

This post is about FRRouting (FRR).
FRR is IP routing protocol suite for Linux and Unix platforms.

Topics which will be covered:
- FRR installation on Ubuntu server
- establishing BGP session between two FRR routers and advertising network via it

BIRD - installation and configuration

This post is about BIRD Internet Routing Daemon.

Topics which will be covered:
- BIRD installation on Ubuntu server
- setting up BGP peering between two servers with BIRD installed
- synchronization of BGP learned route with kernel forwarding table

KVM, Ubuntu and unnatended installation

Starting idea behind that post was to learn about KVM and have possibility to create lab/test VM's in automated way.

As a result bash scripts were prepared for:
- creation of unattended installation ISO with Ubuntu Bionic server (using kickstart and preseed)
- creation of unattended installation ISO with Ubuntu Focal (using cloud-init config)
- VM deployment in KVM with Ubuntu server installed from prepared ISO

Git repository with mentioned scripts and readme files can be found here.

Accessing Arista device eAPI using python

This blog entry is about accessing Arista device eAPI using python.

Topics which will be covered:
- enabling eAPI and creating user for authentication on Arista device
- preparation of Docker container with python and needed library installed
- python code for accessing Arista eAPI

mtr - friend in network troubleshooting

In various scenarious of computer networks troubleshooting, mtr can provide valuable input about path and possible problem location.

Using Ansible for generating configuration files

In this post I want to write about how Ansible and Jinja2 templates can be utilised for generating configuration files (sample configuration for network devices will be prepared).

Topics which will be covered:
- preparation of Ansible files for config generation (Jinja2 template, playbook, inventory, files with variables)

- preparation of Docker container with Ansible installed

Accessing Arista via Ansible

This blog entry is regarding accessing Arista device via Ansible.

Topics which will be covered:
- preparation of Ansible files which will allow for accessing Arista device (playbook, inventory, configuration)
- preparation of Docker container with Ansible installed (needed files for accessing Arista device will be placed in container)

Docker - useful commands

#List running docker container's
docker ps

#List docker container's
docker ps -a

#Access shell of the container
docker exec -i -t id_of_container /bin/bash

GRE tunnel between two F5 LTM's

This blog entry is about creating GRE tunnel between two F5 LTM unit's. In the lab environment where setup was created virtual editions of F5 LTM's were used.

Description and examples of PVST+ operations

This blog entry will be about Spanning-Tree protocol. Whenever I wanted to know how exactly STP would behave in specific situations and how long it would take for network to reconverge - it appears that I needed to review some aspects of STP operations or simply I did not understand the subject good enough. I decided to make summary from my findings and tests, so the next time I will be in doubt about my understanding of STP - it will be easier to refresh the topic.

At first basic operations of STP will be briefly described and then specific scenarios will be presented.

Cisco PVST+ version of Spanning Tree Protocol is covered in this article.

F5 LTM - useful commands

#Create node
tmsh create ltm node node_name address 192.168.0.1

#Create pool
create ltm pool pool_name members add { node_name1:port_number node_name2:port_number  } monitor monitor_name

#Create snatpool
create ltm snatpool snatpool_name members add {192.168.0.1}

Linux - examples of using curl

- Display only headers from the http response
curl -I URL

- Get towards IP using specific "Host" header
curl --header "Host: hostname"  http://IP_Address/path_to_file

- Conditional GET using "ETag"
curl URL --header 'If-None-Match: "aaaaaa-bbbbbbbbbbbbb"'

Cisco - useful commands

#To copy file from server to Cisco device (command executed on Cisco device)
copy scp://username@server_IP//path_to_file/file_name flash:file_name

#To create md5 checksum of the file
verify /md5 flash:file_name

#To set up boot from new image
configure terminal
boot system flash:file_name

#To check md5 checksum on Cisco Nexus
show file bootflash:file_name md5sum

#To upgrade Cisco Nexus (kickstart and system)
install all kickstart kickstart_file_name system system_file_name

#To copy files to Cisco ASA (command executed on the server)
#Username on Cisco ASA need to have proper privilege level
scp -1 -v file_name username@ASA_IP:disk0:file_name
scp -2 -v file_name username@ASA_IP:disk0:file_name

Securing access to Cisco device - login/password

This blog entry is about securing access to Cisco device using password and login combination. Users in presented examples will be configured locally on Cisco device.

Examples of such scenarios will be presented:

1. Setting the privileged level password.
2. Setting privileged level secret.
3. Configuring password checking on vty lines.
4. Configuring password checking on console line.
5. Configuring login and password checking on vty lines.
6. Configuring login and password checking on console line.
7. Configuring login and password checking on vty lines using "aaa new-model".
8. Configuring login and password checking on console line using "aaa new-model".

Packet Capture - ASA

On Cisco ASA there is possibility to configure traffic capturing.

In this blog entry configuration for simple packet capture on Cisco ASA will be presented.

#To start and configure the capture
capture captra interface inside match ip 192.168.1.2 255.255.255.255 10.1.1.1 255.255.255.255

#To view captured packets
show capture captra

#To stop the configured capture
no capture captra interface inside

#To remove the configured capture
no capture captra

#To clear the capture buffer
clear capture captra

Packet Capture - ASR

On the Cisco ASR platform - Embedded Packet Capture (EPC) tool is available. It allows for capturing and analyzing the packets flowing to, from and through the device.

The configuration process of EPC is similar to configuration of packet capturing on Cisco 4500x platform (description of capturing the packets on Cisco 4500x platform can be found under this link - Packet Capture - VSS )

In that blog entry configuration for simple capture on Cisco ASR platform will be presented:

#Configuration of access list which defines traffic for capture
ip access-list extended aclcaptra
permit udp host 192.168.1.1 host 192.168.1.2
permit udp host 192.168.1.2 host 192.168.1.1

#Configuration for capture details
monitor capture captra access-list aclcaptra
monitor capture captra limit duration 200
monitor capture captra interface GigabitEthernet 0/1
monitor capture captra buffer circular size 10

#To start capture process
monitor capture captra start

#To display the captured packets
show monitor capture captra buffer brief

#To clear the capture buffer
monitor capture captra clear