Filtering traffic with vlan access list

Topology Lab setup Linux 2 belongs to vlan 10. Linux 3 and 4 belong to vlan 20. Router is the dhcp server for vlan 10 and 20. A default route goes from Router to the internet where the web application DVWA resides. VLAN 10 subnet and VLAN 20 subnet Damn Vulnerable Web Application … Continue reading Filtering traffic with vlan access list


Multiple Spanning Tree Protocol (802.1s)

This protocol is inspired by Cisco proprietary Per-Vlan Spanning tree plus (PVST+). Cisco PVST+ creates an STP instance for each Vlan. MSTP has more flexibility than PVST+, MSTP instances can map unlimited number of Vlans. MSTP supports 16 STP instances. When MSTP is enabled, RSTP is essentially enabled as well. The disadvantage of PVST+ is … Continue reading Multiple Spanning Tree Protocol (802.1s)

Spanning Tree Protocol (802.1D)

This protocol prevents bridging loop created by redundant links within switch network. STP calculation will make switch/es block its own port so that the switch path is one straight line and not a loop. This is perhaps the most confusing concept in switch, it is not extremely difficult but many terminologies and the method on … Continue reading Spanning Tree Protocol (802.1D)

Catalyst Switch: Turn off trunking negotiation

To turn off dynamic trunking protocol (DTP) and use dot1q standard. It is recommended to turn off trunking protocol and put vtp to transparent mode, this is because a newly introduced Catalyst switch may form undesired switch topology and if the newly introduced Catalyst switch has a vtp revision number higher than the current switch … Continue reading Catalyst Switch: Turn off trunking negotiation

Catalyst Switch: No trunks is formed

I have connected two Cisco Catalyst 3560 switches together by a pair of fibre cables. No trunk was formed. The default interface configuration for Catalyst 3560 is dynamic auto, in Catalyst 3550 the default was dynamic desirable. Dynamic desirable is actively negotiating a trunk with another cisco catalyst switch, whereas dynamic auto is passively waiting … Continue reading Catalyst Switch: No trunks is formed

Cisco IE3000: Resilient Redundancy Protocol

IE3000 is a din-rail mount switch with eight fast ethernet copper ports and two gigabit ethernet combo ports. People who worked for datacentre, enterprise, and ISP might not have seen or used this kind of switch before. The IE3000 is designed for used in Industrial network, most of the control systems like PLCs are mounted … Continue reading Cisco IE3000: Resilient Redundancy Protocol