network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
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Saturday, October 20, 2012

post 600...

that's 50 posts a month average... since november 2011...

to celebrate, we take a look at synchronization...

eigrp and ospf have somewhat similar ideas about synchronization, bgp on the other hand (of course) gives it an entirely different meaning...


in eigrp, synchronization is synonymous with network convergence...


Diffusing Update Algorithm (DUAL) algorithm guarantees loop-free operation at every instant throughout a route computation and allows all devices involved in a topology change to synchronize at the same time. Routers that are not affected by topology changes are not involved in recomputations. The convergence time with DUAL rivals that of any other existing routing protocol.

ospf's synchronization concern is it's database, naturally with the intent to form adjacencies... 

from rfc 2328:

7.2.  The Synchronization of Databases

        In a link-state routing algorithm, it is very important for all
        routers' link-state databases to stay synchronized.  OSPF
        simplifies this by requiring only adjacent routers to remain
        synchronized.  The synchronization process begins as soon as the
        routers attempt to bring up the adjacency.

with bgp, however:

If your AS passes traffic from another AS to a third AS, BGP should not advertise a route before all routers in your AS learn about the route via IGP. BGP waits until IGP propagates the route within the AS and then advertises it to external peers. A BGP router with synchronization enabled does not install iBGP learned routes into its routing table if it is not able to validate those routes in its IGP. Issue the no synchronization command under router bgp in order to disable synchronization. This prevents BGP from validating iBGP routes in IGP. Refer to BGP Case Studies: Synchronization for a more detailed explanation.


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