What does parallelism look like in SQL? How would you know when SQL is doing it parallel style? When looking at sys.sysprocesses you might see something like the below,

CXPACKET_SYSSYSPROCESSES

Here we see many instances of the CXPACKET waittype running seemingly from one spid. The CXPACKET waittype pops up whenever a thread running in parallel is waiting on another thread to complete before the overall process can complete. If you’re seeing CXPACKETs then you’re seeing parallelism. If you see CXPACKETs persist, then there might be an issue slowing down your query, but thats for another story . . . (more info on this waittype here)

The most obvious way to see parallelism is in the query plan. As shown below,

parallel_query_plan

You see this, you’re seeing parallelism :) Painless.

Connecting network devices together isn’t just a case of randomly plugging in cable, care must be taken regarding the type of cable used for the connection

There are three types of cabling,

  • Straight-through, used between devices which are different.
  • Cross-over, used between devices that are the same
  • Roll over, used to connect a computer to the console port of a switch/router so it can be configured
types of cable

Types of Cable

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Redistribution is a means to to propagate routes from one routing protocol to another.

Observe the topology diagram below.

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OSPF is not EIGRP. The process of forming adjacency in OSFP is a much more complex affair involving many more steps than EIGRP. This increased complexity  can deny a network admin the opportunity to really appreciate what is actually happening between two routers.

The process of forming adjacency is outlined below.

1. A new router is introduced to the OSPF area
2. The new Router says Hello.
3. The Hello packet is interrogated by the existing Router
4. Routers are added to Neighbour tables
5. Master and Slave router roles are allocated
6. Database Descriptions are shared
7. DBDs are loaded into memory and examined
8. Requests for more information are sent
9. Neighbours are synchronised

Lets go through the steps one by one explaining the processes, the states the routers enter into and the packets that are shared.
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EIGRP is  a CISCO specific routing protocol. This blog post aims to provide a basic outline of the configuration needed to set it up on a group of routers.

Here we have a simple Hub and Spoke topology between three routers; Jeremy, Geoff and Steve.

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