From: Tim Fletcher (tim@fletchmail.net)
Date: Thu Dec 19 2002 - 13:33:35 GMT-3
At 12:02 PM 12/19/2002 +0000, Sara Li wrote:
>could you share with your experience on ISDN? like which method to use,
>dialer-watch/Demand-circuit?
The method you use depends on the lab requirements. Most labs will give you
some kind of clue what to use, you just have to know the differences to be
able to choose one that meets the requirements. I will try to highlight
some of the differences between some of the different technologies.
Backup Interface
Shuts down the backup interface until the primary interface goes down. It's
the equivalent of doing a shut on the backup interface when the primary
interface comes up, and a no shut when the primary interface goes down.
- The backup interface does not have to be a dial interface.
- Dial connections will still use interesting traffic to bring them up and
idle out.
- The primary physical interface must go down, before the backup can come
up, so some frame scenarios will not work.
- Interesting traffic cannot bring the link up when the primary is up.
Dialer Watch
Forces a dial connection when all of the routes in dialer watch-list
disappear from the routing table.
- Only works with dial interfaces.
- You can have multiple entries in a dialer watch-list.
- Doesn't care about interesting traffic, stays up until the primary routes
are restored (although interesting traffic may be used to bring up
additional links).
- Checks to see if the primary routes are restored every idle-timeout
intervals.
- Because it nails the link up, idle-timeout on the other end will cause
the link to bounce every idle-timeout interval.
- Interesting traffic can still bring the link up
Demand Circuit
Only prevents hellos from keeping the link up.
- Any topology change will bring the link up.
- Only works with OSPF
Snapshot routing
Works with DV protocols.
- Brings the link up at preset intervals to exchange routes.
- Topology changes do not get propagated until the interval expires.
.
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