OSPF

Various

DE-LIST: an ACL which allows traffic to NOT be DE marked (primarily for routing protocols) [Frame-Relay]

ABR, type 3 LSA filtering, see my blog posting

Log redistributed routes, two levels configurable:

  • redistribute maximum-prefix [MAX] [%] warning-only

Will generate a warning message when % of MAX has been exceeded and another when MAX is exceeded. Without the key word warning-only the % defines the warning and MAX is the adsolute maximum number of routes inserted into the backbone area (area 0).

OSPF Passive-interfaces, will not send or receive OSPF traffic.

Virtual-link authentication

Virtual-link interfaces use the same authentication as is enabled for the backbone area. so if area 0 uses authentication and the transit area doesn’t use the following config to disable authentication on the virtual-link:

area 123 virtual-link 3.3.3.3 authentication null
(area <transit area> virtual-link <remote router-id> ...)

!! Be careful though, if it is stated that area 0 should use authentication then the virtual-link is an extension of that. Better ask the proctor and propose to add authentication to the virtual-link(s). Make sure to check the status of the virtual-link (show ip ospf virtual-links) and that the neighborship is up:

R2(config-router)#do ion (sh ip ospf neighbor)
Neighbor ID_____Pri___State_______Dead Time___Address_________Interface
3.3.3.3___________0___FULL/__-_______-________152.1.123.3_____OSPF_VL2

How to make a router (ABR) the least preferred route:

R1(config-router)#max-metric ?
__router-lsa__Maximum metric in self-originated router-LSAs

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