IP Routing Table

Answered Question

Can someone please give me an explanation of this output when I show a spefic route in the routing table.


6509#show ip ro 10.18.12.0

Routing entry for 10.18.12.0/24

Known via "ospf 1", distance 110, metric 4, type inter area

Last update from 10.255.255.37 on GigabitEthernet3/1, 00:00:01 ago

Routing Descriptor Blocks:

* 10.255.255.37, from 10.255.250.8, 00:00:01 ago, via GigabitEthernet3/1

Route metric is 4, traffic share count is 1

10.255.255.33, from 10.255.250.8, 00:00:01 ago, via GigabitEthernet3/2

Route metric is 4, traffic share count is 1


There appears to be two possible routes but one has an asterix next to it. Is this the preferred route and the next one is a backup? Or is traffic being shared amongst these two paths. In the main routing table I can see only one route present.


6509#show ip ro | in 10.18.12.0

O IA 10.18.12.0/24 [110/4] via 10.255.255.37, 00:00:01, GigabitEthernet3/1


Correct Answer by Jon Marshall about 7 years 9 months ago

Jim


The asterix represents which of the 2 routes is being used at any one time. You have 2 equal cost routes so both will be used and the router will switch between the routes either on per packet or per destination.


The reason you are only seeing one route in the routing table with the command


6509#show ip ro | in 10.18.12.0

O IA 10.18.12.0/24 [110/4] via 10.255.255.37, 00:00:01, GigabitEthernet3/1


is because you are using the wrong command. That command will only show lines which include '10.18.12.0'.


Try this command instead "sh ip ro | begin 10.18.12.0" and you should see both routes in the routing table.


Jon


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Correct Answer
Jon Marshall Thu, 06/11/2009 - 02:27
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Jim


The asterix represents which of the 2 routes is being used at any one time. You have 2 equal cost routes so both will be used and the router will switch between the routes either on per packet or per destination.


The reason you are only seeing one route in the routing table with the command


6509#show ip ro | in 10.18.12.0

O IA 10.18.12.0/24 [110/4] via 10.255.255.37, 00:00:01, GigabitEthernet3/1


is because you are using the wrong command. That command will only show lines which include '10.18.12.0'.


Try this command instead "sh ip ro | begin 10.18.12.0" and you should see both routes in the routing table.


Jon


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