07-19-2006 05:30 AM - edited 03-05-2019 11:59 AM
what is routingloop and how it occures in routing? how can i implement in my lab?
dporter
07-19-2006 05:57 AM
Here's a few links to get started.
http://www.answers.com/topic/routing-loop
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/routing.htm
07-19-2006 06:04 AM
You have 2 types of routing loops.
The first loops the traffic and the other loops the routing table entries themselves.
A traffic loop is easy to do.
Just put in the same static route in 2 routers and point them to each other.
For example
If you have router A with ip address 192.168.1.1 and router b wiht ip address 192.168.1.2
In router A put in
IP route 10.10.10.0 255.255.255.0 192.168.1.2
in router b put in
ip route 10.10.10.0 255.255.255.0 192.168.1.1
now ping 10.10.10.1 from either router.
A routing loop of the routing table itself is very complex to simulate and very hard to fix.
Basically it is caused by route redistribution on multiple routers. A single routing protocol is smart enough to know that I do not want to learn a route that I just sent to another router. When you convert routes from one routing protocol to another some of this information is lost.
For this second kind of loop you need a good understatnding of administative distance. I do not have a simple example of how to do this since it in most cases will require 3 or 4 routers to get loop that will be of any interest to look at.
07-19-2006 06:04 AM
Hello,
A routing loop comes from error in your routing configuration. For example if you have two routers connected together A and B and that A beleives that subnet X is reachable via B and B beleives that the subnet X is reachable via A, a packet destinated to X will loop between A and B until its TTL reaches 0.
These loop comes often from redistribution between different routing process with some misconfiguration. The following document shows some example: http://www.cisco.com/en/US/tech/tk365/technologies_white_paper09186a0080531fd2.shtml
However the easiest way to get a routing loop in your lab is to configure static routes :
RouterA
ip route X.X.X.X B.B.B.B
RouterB
ip route X.X.X.X A.A.A.A
Please rate if it helps.
Regards,
Christophe
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