10-29-2011 01:26 AM - edited 03-07-2019 03:07 AM
hi:
i am doing experiment with RIP.
the toppology is as follow
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.
Solved! Go to Solution.
10-29-2011 02:19 AM
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
10-29-2011 02:26 AM
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
10-29-2011 01:44 AM
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
10-29-2011 01:49 AM
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
10-29-2011 01:57 AM
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 .
10-29-2011 02:19 AM
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
10-29-2011 02:26 AM
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
10-29-2011 02:38 AM
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.
10-29-2011 03:52 AM
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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