CCNA Notes : cont...
52. The metric limit for link-state protocols is 65,533
53. Following are the possible solutions for preventing routing
loops.
1.
Split Horizon - based on the principle that it is not useful to send
the information about a route back in the direction from which the
information originally came.
2.
Poison Reverse - A router that discovers an inaccessible route sets
a table entry consistent state (infinite metric) while the network
converges.
3.
Hold-down Timers - Hold down timers prevent regular update messages
from reinstating a route that has gone bad. Here, if a route
fails, the router waits a certain amount of time before accepting
any other routing information about that route.
4.
Triggered Updates - Normally, new routing tables are sent to
neighboring routers at regular intervals (IP RIP every 30 sec / and
IPX RIP every 60 sec). A triggered update is an update sent
immediately in response to some change in the routing table.
Triggered updates along with Hold-down timers can be used
effectively to counter routing loops.
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