Category Archives: Switch

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 … Continue reading

Posted in General stuffs, Security, Switch, Vlan | Tagged , | 1 Comment


Stack master election criteria The criteria is in order, if the first criteria does not meet the second criteria will be the tie breaker. 1. The switch that is configured with the highest stack priority. 2. The switch that is … Continue reading

Posted in High Availability, Stackwise, Switch | Tagged , , | 2 Comments

IOS installation for Catalyst 3750 switch

Precaution 1. When adding an additional switch to the current switch stack always check the new switch IOS version first. 2. If the new switch is added to the current stack and if the IOS is mismatched the stack knows … Continue reading

Posted in Network Maintenance, Stackwise, Switch | Tagged , , , , , | 1 Comment

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. … Continue reading

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Rapid Spanning Tree Protocol (802.1w)

Port roles 1. Root port – STP path that is “shortest” to root bridge. 2. Designated port – Port that is forwarding and is not a root port. 3. Alternate port – Backup root port. Present the alternate path to … Continue reading

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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 … Continue reading

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VLAN Trunking Protocol

This is a Cisco proprietary protocol that is designed to ease Vlan database management, it has nothing to do with trunking. The concept is that a switch with a VTP server mode will propagate VLAN database down to all switches … Continue reading

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