Tag Archives: network

Boost Ubuntu 16.04/17.10 Network Performance by Enabling TCP BBR

Install Linux Kernel 4.9 or Above
TCP BBR is supported by Linux since kernel version 4.9. Use the following command to check your Linux kernel version.

uname -r

Simply install the Hardware Enablement Stack (HWE), which provides newer kernel for Ubuntu LTS releases

sudo apt install --install-recommends linux-generic-hwe-16.04
sudo nano /etc/sysctl.conf
net.core.default_qdisc=fq
net.ipv4.tcp_congestion_control=bbr
sudo sysctl -p

References
https://www.linuxbabe.com/ubuntu/enable-google-tcp-bbr-ubuntu

Configure DHCP server on cisco router

tk-cisco-routers-dhcp-1

R1# configure terminal
R1(config)# service dhcp
R1(config)# ip dhcp pool NET-POOL
R1(dhcp-config)# network 192.168.1.0 255.255.255.0
R1(dhcp-config)# default-router 192.168.1.1
R1(dhcp-config)# dns-server 192.168.1.5 195.170.0.1
R1(dhcp-config)# domain-name Firewall.cx
R1(dhcp-config)# lease 9
R1(config)# ip dhcp excluded-address 192.168.1.1 192.168.1.5
R1(config)# ip dhcp excluded-address 192.168.1.10
R1# show ip dhcp binding

References :

http://www.firewall.cx/cisco-technical-knowledgebase/cisco-routers/812-cisco-router-dhcp-config.html

Cisco RIP v2 IP Routing

RIPv2-2

RouterA(config)#router rip
RouterA(config-router)#version 2
RouterA(config-router)#network 192.168.10.0
RouterA(config-router)#network 195.14.25.0
RouterA(config-router)#network 195.14.125.0
RouterA(config-router)#no auto-summary

RouterB(config)#router rip
RouterB(config-router)#version 2
RouterB(config-router)#network 192.168.20.0
RouterB(config-router)#network 195.14.25.0
RouterB(config-router)#network 195.14.125.0
RouterA(config-router)#no auto-summary

RouterC(config)#router rip
RouterC(config-router)#version 2
RouterC(config-router)#network 192.168.30.0
RouterC(config-router)#network 195.14.25.0
RouterC(config-router)#no auto-summary

References :

http://blog.pluralsight.com/cisco-how-to-configure-rip-2

Cisco RIP v1 IP Routing

RIPv1-1

RouterA(config)#router rip
RouterA(config-router)#network 192.168.10.0
RouterA(config-router)#network 195.14.25.0
RouterA(config-router)#network 195.14.125.0

RouterB(config)#router rip
RouterB(config-router)#network 192.168.20.0
RouterB(config-router)#network 195.14.25.0
RouterB(config-router)#network 195.14.125.0

RouterC(config)#router rip
RouterC(config-router)#network 192.168.30.0
RouterC(config-router)#network 195.14.25.0

References :

http://blog.pluralsight.com/cisco-how-to-configure-rip-1

Calculate IP


Address: 192.168.0.1 11000000.10101000.00000000 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
=>
Network: 192.168.0.0/24 11000000.10101000.00000000 .00000000 (Class C)
Broadcast: 192.168.0.255 11000000.10101000.00000000 .11111111
HostMin: 192.168.0.1 11000000.10101000.00000000 .00000001
HostMax: 192.168.0.254 11000000.10101000.00000000 .11111110
Hosts/Net: 254 (Private Internet)

References :

http://jodies.de/ipcalc

Broadcast address

IP

The broadcast address for an IPv4 host can be obtained by performing a bitwise OR operation between the bit complement of the subnet mask and the host’s IP address. In other words, take the host’s IP address, and set to ‘1’ any bit positions which hold a ‘0’ in the subnet mask.

Example: For broadcasting a packet to an entire IPv4 subnet using the private IP address space 172.16.0.0/12, which has the subnet mask 255.240.0.0, the broadcast address is 172.16.0.0 | 0.15.255.255 = 172.31.255.255.

255.240.0.0=11111111.11110000.00000000.00000000
172.16.0.0=10101100.00010000.00000000.00000000
10101100.00011111.11111111.11111111=172.31.255.255

Ethernet

Broadcast is possible also on the underlying Data Link Layer in Ethernet networks. Frames are addressed to reach every computer on a given LAN segment if they are addressed to MAC address FF:FF:FF:FF:FF:FF. Ethernet frames that contain IP broadcast packages are usually sent to this address.

References :

https://en.wikipedia.org/wiki/Broadcast_address