network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
a network runs through it

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Sunday, November 25, 2012

bgp preferences...

it's kinda like a woman... size matters in the early stages...

1. weight (bigger)
2. local preference (bigger)
3. locally originated

one moment here...  this means THIS router generated it...

the rest are smaller, or littler, or older or more shriveled...

4. as-path (lowest)
5. origin

meaning code or type... i before e and question mark last... however, there are no e's (external gateway protocol) anymore... ? means learned through redistribution...

6. med (lowest)

multi-exit discriminator means just the opposite for the local router; the paths coming into, not out of... i hate that shit...

how cisco puts it...

MED is an optional nontransitive attribute. MED is a hint to external neighbors about the preferred path into an autonomous system (AS) that has multiple entry points. The MED is also known as the external metric of a route. A lower MED value is preferred over a higher value.

7. external, or EBGP over IBGP
8. IGP cost (smaller)
9. EBGP Peering (age; older)
10. RID (lower)

synchronization side note...

from cisco wiki:


When an AS provides transit service to other ASs and if there are non-BGP routers in the AS, transit traffic might be dropped if the intermediate non-BGP routers have not learned routes for that traffic via an IGP. The BGP synchronization rule states that if an AS provides transit service to another AS, BGP should not advertise a route until all of the routers within the AS have learned about the route via an IGP.

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