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RIP route selection question

hi:

i am doing experiment with RIP.

the toppology is as follow

2011-02-18_155451.jpg

The RIP v2 set up was successful however when i try to  trace the packet , i realised the  the router on the right  always send packet via S3/0

why didn't it choose fa1/0 ? 

is it some kind of load balance? 

thanks in advance.

Everyone's tags (1)
2 ACCEPTED SOLUTIONS

Accepted Solutions

RIP route selection question

Hi Dannan

RT has two equal cost paths for 1.1.1.1 and hence it has to load-balance but may be seems somewhere my understanding on interpreting the trace ouput is incoherent with the LB. This is a traffic which is originating from the router and not a transit traffic and hence should be process-switched on a round-robin basis.

Can you please try to traceroute multiple times with different source IPs ie once Source as 21.1.1.2 ( take 2 snapshots) and then source as 12.1.1.2 (take two snapshots)  and post the results.

Regards

Varma

New Member

Re: RIP route selection question

Hi,

R       1.1.1.0 [120/1] via 21.1.1.1, 00:00:28, FastEthernet1/0

                [120/1] via 12.1.1.1, 00:00:28, Serial3/0

From here it is clear that the remot n/w is learned by using two interface and it is of same cost. Since it is haveing same cost it will loadbalance with an algorithm called " round robin load balance".

Also RIP can support up to 6 equal path( 4 by default).

HTH

Please rate this post if you find this helpful

Thanks

Vipin

Thanks and Regards, Vipin
7 REPLIES

RIP route selection question

Hi Dannan

This does not seem to be any kind of load-balancing to me personally. Can you please share the output of below command

"sh ip route 1.1.1.1"  and "sh ip rip database "

Regards

Varma

New Member

Re: RIP route selection question

Hi,

it is definetly not a load balace, since RIP is using hop count as metric.

Could you please provide output of "sh ip route"

Thanks

Vipin

Thanks and Regards, Vipin
New Member

RIP route selection question

thanks for your reply.

I think it could be load balance as well.  because i ran "trace 1.1.1.1 " command several times ,router choosed different port.

the output looks like below


  1   21.1.1.1        6 msec    3 msec    1 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   12.1.1.1        10 msec   5 msec    6 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   21.1.1.1        11 msec   4 msec    4 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   12.1.1.1        11 msec   6 msec    6 msec

below is the routing table:

     1.0.0.0/24 is subnetted, 1 subnets

R       1.1.1.0 [120/1] via 21.1.1.1, 00:00:28, FastEthernet1/0

                [120/1] via 12.1.1.1, 00:00:28, Serial3/0

     2.0.0.0/24 is subnetted, 1 subnets

C       2.2.2.0 is directly connected, Loopback0

     12.0.0.0/24 is subnetted, 1 subnets

C       12.1.1.0 is directly connected, Serial3/0

     21.0.0.0/24 is subnetted, 1 subnets

C       21.1.1.0 is directly connected, FastEthernet1/0     1.0.0.0/24 is subnetted, 1 subnets
R       1.1.1.0 [120/1] via 21.1.1.1, 00:00:28, FastEthernet1/0
                [120/1] via 12.1.1.1, 00:00:28, Serial3/0
     2.0.0.0/24 is subnetted, 1 subnets
C       2.2.2.0 is directly connected, Loopback0
     12.0.0.0/24 is subnetted, 1 subnets
C       12.1.1.0 is directly connected, Serial3/0
     21.0.0.0/24 is subnetted, 1 subnets
C       21.1.1.0 is directly connected, FastEthernet1/0

if it is loadbalance ?  what kind of loadbalance is this ? (process based? )

is there any particular rule to choose which port to send packet first?

thanks for your help .

RIP route selection question

Hi Dannan

RT has two equal cost paths for 1.1.1.1 and hence it has to load-balance but may be seems somewhere my understanding on interpreting the trace ouput is incoherent with the LB. This is a traffic which is originating from the router and not a transit traffic and hence should be process-switched on a round-robin basis.

Can you please try to traceroute multiple times with different source IPs ie once Source as 21.1.1.2 ( take 2 snapshots) and then source as 12.1.1.2 (take two snapshots)  and post the results.

Regards

Varma

New Member

Re: RIP route selection question

Hi,

R       1.1.1.0 [120/1] via 21.1.1.1, 00:00:28, FastEthernet1/0

                [120/1] via 12.1.1.1, 00:00:28, Serial3/0

From here it is clear that the remot n/w is learned by using two interface and it is of same cost. Since it is haveing same cost it will loadbalance with an algorithm called " round robin load balance".

Also RIP can support up to 6 equal path( 4 by default).

HTH

Please rate this post if you find this helpful

Thanks

Vipin

Thanks and Regards, Vipin
New Member

RIP route selection question

thanks guys,

\

it is a loadbalance , but i still want to know if there is any particular rule to use certain port to send packet first . in my case, why it aways choose 21.1.1.1 ????

below is my trace output :

Router#
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   21.1.1.1        30 msec   11 msec   1 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   12.1.1.1        33 msec   5 msec    6 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   21.1.1.1        25 msec   2 msec    5 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   12.1.1.1        21 msec   3 msec    3 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   21.1.1.1        25 msec   5 msec    3 msec   
Router#trace 1.1.1.1
Type escape sequence to abort.
Tracing the route to 1.1.1.1

  1   12.1.1.1        24 msec   5 msec    4 msec   

thanks.

RIP route selection question

Hi Danna,


it is a loadbalance , but i still want to know if there is any particular rule to use certain port to send packet first . in my case, why it aways choose 21.1.1.1 ????

You can use something called PBR(policy based routing) where you can specify which interface the packet should exit from your device using "set-interface " command

please see the below link.

http://www.cisco.com/en/US/docs/ios/12_0/qos/configuration/guide/qcpolicy.html

HTH

Kishore

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