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RIPv2


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#31 lthebe

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Posted 04 June 2010 - 06:53 PM

RIPv2

RIPv2 Summary
The characteristics of RIPv2 follow:

 Distance-vector protocol.

 Use UDP port 520.

 Makes Automatic summarization on network Class boundary.

 Classless protocol (supports VLSMs).

 Have the power to shut the Auto-summarization And make a configured manual Summarization.

 Supports VLSMs.

 Metric is router hop count.

 Maximum hop count is 15; infinite (unreachable) routes have a metric of 16.

 Periodic route updates sent every 30 seconds to multicast address 224.0.0.9.

 25 routes per RIP message (24 if authentication is used).

 Invalid route marked after 180 sec.

 Flush timer is 280 sec.

 Hold-down timer 180 sec.

 Supports authentication.

 Implements split horizon with poison reverse.

 Implements triggered updates.

 Subnet mask included in route entry.

 Administrative distance for RIPv2 is 120.

 Used in small, flat networks or at the edge of larger networks.


RIPv2 Convergence

The steps for RIPv2 convergence are as follows:

1- When the local router sees a connected route disappear, it sends a
Flash update and removes the route entry from its table. This is
Called a triggered update with poison reverse.

2- The receiving routers send a Flash update and put the affected route
in holddown.

3- The originating router queries its neighbor (DC) for alternative routes.
If the neighbor has an alternative route, it is sent; otherwise, the
Poisoned route is sent.

4- The originating router installs the best alternative route that it
hears because it has purged the original routes, and Send the new updates in
its periodic routing update timer (30 sec).

5- Routers that are in holddown ignore only the alternative route.

6- When the other routers emerge from holddown, they will accept
the alternative route.

7- Convergence takes the time for detection, plus holddown, plus the
number of routing updates (equal to the hop-count diameter of the network).
This could take a long time.



RIP v2 Configuration

config)# router rip
conf-router)# version 2
conf-router)# no auto-summary
conf-router)# network < classfull Net ID>

conf-router)#passive-interface <interface>

conf-router)#maximum –paths <N> (Up to 6 Links for load sharing on a R.B basis, Over equal metric paths default =is 4 paths)

conf-if)# no ip split-horizon (Disables it from a specific interface)
c
onf-router)#distance <N> (Define an administrative distance, default =120)

conf-router)# timers basic < update - invalid –holdown –flush – sleep > (Adjust timers in sec , Sleeptime is a timer used to specify a period, in milliseconds, to delay a regular routing update after receiving a triggered update.)

conf-router)# neighbor < ip add> (Because RIP is a broadcast protocol you may configure RIP to exchange routing information in a Point-Point non-broadcast network such as Frame Relay. In this type of network, RIP must be informed of neighbor RIP routers, Also When it is used in combination with the passive-interface cmd, routing information can be Only exchanged between the router and this nei Ex. Unix server on a LAN )

conf-router)#validate-update-source (This command is applicable only to RIP and IGRP. The software ensures that the source IP address of incoming routing updates is on the same IP network as one of the addresses defined for the receiving interface. Disabling split horizon on the incoming interface will also cause the system to perform this validation check. For unnumbered IP interfaces (interfaces configured as IP unnumbered), no checking is performed. )

conf-router)# no auto-summary
conf-if )# ip summary-address rip < Net ID + mask>


Show Commands

# sh ip route
# sh ip route rip
# sh ip route < Net ID >
# sh ip rip database
# sh ip protocols

#debug ip rip
#debug ip rip events
# no debug all


Hope this might be usefull

I guess the flush timer should be 240 which is 60 seconds greater than invalid timer!
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#32 rax369

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Posted 06 June 2010 - 07:47 AM

I guess the flush timer should be 240 which is 60 seconds greater than invalid timer!


That's exactly what I was going to say... there's an error there. Actually the flush timer is 8 times greater than the default update timer (and either the invalid and the holdown timer are 6 times greater).

This is the easy way I learned myself the time for the 4 RIP's timers:

Update Timer = 30 seconds
Invalid Timer = 6 x 30 = 180 seconds
Holddown Timerr = 6 x 30 = 180 seconds
Flush Timer = 8 x 30 = 240 seconds

Hence correct time period for this timer is 240, as follows...

Taken from "Sybex - CCNA Study Guide 6th Edition (2007), page 383":

RIP Timers
RIP uses four different kinds of timers to regulate its performance:

Route update timer Sets the interval (typically 30 seconds) between periodic routing updates
in which the router sends a complete copy of its routing table out to all neighbors.

Route invalid timer Determines the length of time that must elapse (180 seconds) before a
router determines that a route has become invalid. It will come to this conclusion if it hasn't
heard any updates about a particular route for that period. When that happens, the router will
send out updates to all its neighbors letting them know that the route is invalid.

Holddown timer This sets the amount of time during which routing information is sup-
pressed. Routes will enter into the holddown state when an update packet is received that indi-
cated the route is unreachable. This continues either until an update packet is received with a
better metric or until the holddown timer expires. The default is 180 seconds.

Route flush timer Sets the time between a route becoming invalid and its removal from the
routing table (240 seconds). Before it's removed from the table, the router notifies its neigh-
bors of that route's impending demise. The value of the route invalid timer must be less than
that of the route flush timer. This gives the router enough time to tell its neighbors about the
invalid route before the local routing table is updated.

PD: Hope it helps! Posted Image

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#33 DarkFiber

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Posted 07 June 2010 - 05:14 AM

Yes guys, i advised its a typo before in a previous post :)
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#34 Smith JohN

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Posted 16 June 2010 - 01:03 PM

Nice share and cool presentation. Thanks buddy!
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#35 LeitoSR

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Posted 22 December 2010 - 08:49 AM

RIPv2

RIPv2 Summary
The characteristics of RIPv2 follow:



 Invalid route marked after 180 sec.

 Flush timer is 280 sec.

 Hold-down timer 180 sec.



Hey DarkFiber, thnx for the nice info.

Can u just Correct the Flush timer to 240 sec, Instead of 280.

flush:

Amount of time in seconds that must pass before the route is removed from the routing table; the interval specified should be greater than the invalid value. If it is less than this sum, the proper holddown interval cannot elapse, which results in a new route being accepted before the holddown interval expires. The default is 240 seconds.

Defaults

update is 30 seconds
invalid is 180 seconds
holddown is 180 seconds
flush is 240 seconds

http://www.cisco.com...ip.html#wp30444


oo i didn't Read the topic to the end,
i noticed now that u said noticed this..

Still hope u edit it for newbie's or Begineers just in case not to mess with their brains. :)

Edited by LeitoSR, 22 December 2010 - 08:52 AM.

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#36 arvinsony

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Posted 26 September 2011 - 04:51 PM

good one dude ......
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#37 NewInBussines

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Posted 22 November 2011 - 06:41 PM

Hi,
This is a very helpful represenation and also the documents are great.

Thanks
Robert
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