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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 [...]

As we mentioned in one of our previous posts, STP was developed to allow redundancy in the L2 network while maintaining a loop free network. Today we are going to discover how STP is actually doing this function. Step1: Electing the root bridge What is the root bridge? The root bridge is the master bridge [...]

Spanning tree protocol or STP is used to provide redundant links in the network while preventing the danger of bridging loops. Our network below has two switches connected to each other by two FastEthernet links for redundancy. In such setups STP is essential to avoid bridging loops. The Problem:How bridging loops happen ? (STP is [...]

Etherchannel is a very effective feature that provides redundancy and load distribution within your switching network. However failing to choose the right load distribution algorithm my leave you under utilizing your network resources. We are going to analyze how to select the load balancing method based on placement of switch and traffic type that needs [...]

Extended VLANs are VLANs within the range of 1006 to 4094. They are mainly used in service provider networks to allow the provisioning of number of customers. In order to configure an extended VLAN you have to follow the guideline below: Extended VLANs are used just like normal VLANs; only different range. Extended VLANs must [...]