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In late 2007, Cisco introduced a new Inter-AS option; Option AB – This feature was introduced in the 12.2(33)SRC code. This feature combines the the best aspects of Option 1 (10A) and Option 2 (10B) (named type a and type b as per RFC4364 section 10 “Multi-AS Backbone”). Remember that type a (Option 1 AKA [...]

By default any interface on the switch can only send or receive a frame of a maximum size 1500 byte. Some applications like (QinQ, MPLS over Ethernet) require increasing the MTU of the switches in your network to allow greater sizes because thier frames may exceed the default 1500 bytes size. You can increase the [...]

BPDUs are the messages exchanged between switches to calculate the spanning tree topology. BPDU filter is a feature used to filter sending or receiving BPDUs on a switchport. It is extremely useful on those ports which are configured as portfast ports as there is no need to send or receive any BPDU messages on of [...]

This is a master piece post from Petr Lapukhov explaining Private VLANs; what are they ? and how to configure and troubleshoot them ?. I am sure you will never get confused by Private VLANs anymore. Private VLANs revisited Read and understand

After explaining how STP works to ensure your network is free of bridging loops in previous posts, we are going directly to a configuration example. We will use a simple topology in the diagram below and configure the switches to accomplish the tasks listed below. Task1: Configure SW0 as a root bridge for both VLAN1,2. [...]

In the first post STP part1, we discussed the root bridge election process, that was the first step in calculating the spanning tree topology. Lets dive and explore step2. Step2: Best Path selection After choosing and agreeing on the root switch for the domain, each switch starts looking for the shortest path to the root [...]