Re: RIP count to infinity and OSPF
- From: bod43 <Bod43@xxxxxxxxxxxxx>
- Date: Sun, 18 Jan 2009 05:37:37 -0800 (PST)
On 18 Jan, 09:32, "syuga2...@xxxxxxxxx" <syuga2...@xxxxxxxxx> wrote:
There is split-horizon, poison-reverse, hold-down, triggered update
mechanisms to handle count to infinity problem in RIP.
I am a bit confused about why so many mechanisms are used?when and in
what practical scenarios is each applicable?
Is there a single mechanism which takes care of count to infinity
problem. For example RIP RFC says that triggered updates need to be
used when there are more than 3 gateways in a routing loop. How does
one know in advance which mechanism to use?
Also, I read some documentation which says that OSPF converges quickly
as compared to RIP bcos it is link state based. What exactly does this
mean? How is a OSPF routing update different from RIP update ?
The best description of these routing protocols that I have seen
is in
Routing TCP/IP, volume 1, second edition
Jefff Doyle
It is widely respected and I have it right here:)
I'll give Link State a quick go.
RIP as you know advertises routes out of each interface.
Each router frequently advertises all of the routes it has
learned about, perhaps with regard to split horizon.
OSPF (and ISIS)
Do not advertise routes.
Ther follows a very brief and idealised description
of the principle of link state routing.
Each router advertises itself and all of the networks to which it is
connected. In this way all routers can construct a
full network diagram. This is called the Topology Database.
Each router then independently
works out which next hop to use
for each destination network. The best of these
is used to construct the routing table for that router.
Once the topology database is constructed no
further updates are sent (sort of:).
OSPF does not therefore need (by principle) the
distance vector tricks and optimisations to control
routing loops and to speed convergance times.
It does however have its own set of tricks and optimisations
which are required to control the volume of updates needed.
Multiple Areas, Designated Routers, Stub areas. Also the
whole topology database is updated periodically.
There will be for sure some decent descriptions on-line
but I cant point you there since I have Doyle already:)
http://www.cisco.com/en/US/docs/internetworking/technology/handbook/OSPF.html
http://www.cisco.com/en/US/tech/tk365/tk480/tsd_technology_support_sub-protocol_home.html
.
- References:
- RIP count to infinity and OSPF
- From: syuga2012@xxxxxxxxx
- RIP count to infinity and OSPF
- Prev by Date: Re: Remote User VPN - ASA 5505 and Client 5.0.02
- Next by Date: Re: Accessing a server from the external IP
- Previous by thread: RIP count to infinity and OSPF
- Next by thread: Re: RIP count to infinity and OSPF
- Index(es):
Relevant Pages
|
