In last 6 months I got opportunity to work closely with HR teams
from different regions within company and must have interviewed well over 200 People which gave me
good opportunity to talk to so many candidates ranging from CCNA to CCIE &
even Multiple CCIEs.
During this whole process I came across couple of Myths related
to IP Networking which I would want to share so that together we can spread
more awareness among other Engineers & Clients.
Myth 1 : vPC eliminates STP into the Network.
Well vPC tweaks STP behavior quite a bit for it’s operation but
STP is still running in backend as fail safe. Even more vPC Primary switch send
regular STP BPDUs by default over vPC member ports. Well the only solution to
get rid of STP completely today from Cisco’s perspective is implementing Fabric
Path.
Myth 2 : EIGRP is a better protocol for Cisco only network since
it has better convergence features such as Feasible Successor if compare to
OSPF. Same thought people have when comparing ISIS with OSPF.
Well convergence in itself is domain now from IP Networking
perspective or perhaps always was. It’s just people these days talk more about
it as requirements have grown tight in last 5 years because of Next Generation
Network Requirements and more sensitive applications.
Most routing protocols don’t spend too much time for
re-calculation once the primary path gets failed. The most contributing factor
in convergence is detection of failure rather. A simple example would be to
have two EIGRP neighbors connected through multiple links including a Ethernet
connection through L2 Switch which is currently primary path. If link between
L2 switch & Router 2 fails, Router 1 will notice the failure only after
dead timer expire and than will run DUAL for recalculation depending upon it
has Feasible successor or not. So in this case it’s not going to be any
different than OSPF or IS-IS.
Myth 3 : OTV is the best solution for VMotion over Data Center
Interconnect (DCI) or any Layer 2 extension requirements.
Well It depends. The part of equation here is VMotion
requirements itself. For Hot VMotion the end to end delay requirements is less
than or equal to 5 msec which in new ESXi version got relaxed to 10 msec I
guess. So if the delay is higher and you have Hot VMotion requirements, OTV
won’t do any good as DCI. Also choosing DCI Technology Between OTV and others
like MPLS Martini Style, VPLS etc has lot to do with Scale related to number of
MAC Addresses to be learned & Exchanged.
Myth 4 : One major benefit of using MPLS is that Router Switches
packets faster since it uses LIB
Well it use be true in history but ever since the introduction
of Hardware based forwarding in platforms and platforms having great amount of
CPU and Memory, it’s not true any longer.
Myth 5 : Nexus 2000 is a Switch
Well it can’t perform local switching between 2 ports which
might be even in Same VLAN. All the switching is still performed by Parent
Switch (7k or 5k) based on VN Tags.
Myth 6 – Once the EIGRP SIA Timer Expires, The Neighbors are
bounced
Well Cisco solved this problem I guess almost 10 years back with
implementation of SIA Query & Replies. It’s just of those things which are
not documented in most Cisco Press Books J covering EIGRP
Myth 7 – Traceroute is part of ICMP Suite
Well traceroute is an application but not a protocol or part of
any protocol suite in itself. Traceroute has different implementations using
ICMP, TCP & UDP by different vendors.
HTH...
Deepak Arora
Evil CCIE
