What is E1 and E2 route

[Deepak Kumar]

Hi All experts,

I am trying to understand a difference between E1 and E2 routes in the OSPF. Please help me to get in technical deep in this topic.

Regards,

Deepak Kumar

[mkazam001]

E1 routes indicate cumulative cost to reach the destination i.e. int indicates cost to reach ASBR + cost to destination from ASBR.

E2 route reflects cost only from the ASBR to destination. This is the default used by ospf for redistribution.

Regards, mk

[balaji.bandi]

From my notes :

E1 or External Type Routes – The cost of E1 routes is the cost of the external metric with the additional of the internal cost within OSPF to reach that network.

E2 or External Type2 Routes – The cost of E2 routes will always be the external metric, the metric will takes no notice of the internal cost to reach that network.

If 2 external type 2 routes exist with the same metric to the same destination the route with the lowest metric to the ASBRwill be used. Also if an E1 and E2 route exist to the same destination the E1 route will always be preferred irrespective of the metric.

Basically difference between E1 and E2 is:

E1 includes – internal cost to ASBR added to external cost,

E2 does not include – internal cost. it is same as external cost.