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Tag: CCIE

CCIE: EIGRP

CCIE: EIGRP

One of my favorite routing subjects to discuss. Usually, I’ll be asked what is a better IGP OSPF or EIGRP and my answer is always… it depends. There a couple compelling reasons why EIGRP is still a great IGP after so many years. Here are a few in my opinion; ease of deployment, convergence speed (without tweaks), and offset capability. Of course, there are some disadvantages; scale, ease of deployment (your not required to take a deep look at your topology like OSPF), and it’s proprietary….

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CCIE: PPP Authentication

CCIE: PPP Authentication

Personally, this is an area that I struggled with during my studies. Not quite sure why, the concept is not that difficult. Perhaps, it’s one of those “boring” subjects and I just could not get excited about it no matter how hard I tried. In real world use cases, I used PPP all the time for the PE to CE encapsulation method. The thing is at the SP, there was no need to “secure” the /30 MPLS circuits so, LCP was…

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CCIE: 802.1s (MST)

CCIE: 802.1s (MST)

Overview: MSTP, which uses RSTP for rapid convergence, enables VLANs to be grouped into a spanning-tree instance, with each instance having a spanning-tree topology independent of other spanning-tree instances. This architecture provides multiple forwarding paths for data traffic, enables load balancing, and reduces the number of spanning-tree instances required to support a large number of VLANs. All the details can be found here. My personal field experience: It’s funny, I always hear how great MST is (and it does have…

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CCIE: Root Guard, BPDU Guard, BPDU Filter, and Loop Guard

CCIE: Root Guard, BPDU Guard, BPDU Filter, and Loop Guard

The BPDU guard feature can be globally enabled on the switch or can be enabled per port, but the feature operates with some differences. At the global level, you enable BPDU guard on Port Fast-enabled ports by using the spanning-tree portfast bpduguard default global configuration command. Spanning tree shuts down ports that are in a Port Fast-operational state if any BPDU is received on them. In a valid configuration, Port Fast-enabled ports do not receive BPDUs. Receiving a BPDU on a Port…

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CCIE: VTP or not to VTP, that is the question.

CCIE: VTP or not to VTP, that is the question.

In *most* productions networks device limitations (VLAN,TCAM entries) must be taken into consideration. This is one of the downsides of using VTP. All switches will get the entire database regardless if they have local assignments or even are in the transit L2 path. Transparent mode and manually creating the necessary VLANs may be your best option. Switches to not create a STP instance for unnecessary VLANs thus conserving resources and CPU cycles. If you are using VTP be sure to enable pruning to conserve bandwidth…

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