"show ip ospf statistics" output interperatation

[scottpickett]

When issuing the command "show ip ospf statistics" a list of information regarding SPF execution and calculation comes up with REASON codes for the execution of SPF.

The IOS command reference lists the reason codes as:

N—A change in a network LSA (type 2) has occurred.

R—A change in a router LSA (type 1) has occurred.

SA—A change in a Summary autonomous system boundary router (ASBR) (SA) LSA has occurred.

SN—A change in a Summary Network (SN) LSA has occurred.

X—A change in an External Type-7 (X7) LSA has occurred.

Is "X" only a Type-7 and not Type-5 because an OSPF router would not run SPF against a change to a Type-5, but only against the ASBR which knows of the External route.

Since a Type-7 is flooded inside a NSSA, a change to a Type-7 would trigger SPF inside the AREA.

Is my understanding right?  At first I thought "X" should be "All external" but now I think the "X" = type-7 makes more sense.

[Giuseppe Larosa · Accepted solution]

Hello Scott,

your understanding is correct type-7 are confined within the NSSA area in which they are originated, and the command reference refers to X7 for type-7.

And yes there is no reference to normal external routes (type 5) SPF is executed to reach the ASBR (code SA)

see

http://www.cisco.com/en/US/docs/ios-xml/ios/iproute_ospf/command/ospf-s1.html#GUID-0C0289E1-7087-43CC-81DC-FAE8A5BCD17E

Hope to help

Giuseppe