Introduction:
The "external-out enable" command is available for configuration under the "router ospf process" in case of the IOS-XR operating system. This command basically enables advertisement of intra-area routes on the device as external routes in the OSPF domain.
Configuration Example:
RP/0/RP0/CPU0:CORE#
router ospf 1
area 0
external-out enable
interface TenGigE0/7/0/15
cost 10
!
interface TenGigE0/7/0/16
cost 10
!
interface TenGigE0/7/0/17
cost 10
!
!
!
end
RP/0/RP0/CPU0:CORE#sh ospf database external self-originate | in State ID
Link State ID: 10.56.232.0 (External Network Number)
Link State ID: 10.56.232.32 (External Network Number)
Link State ID: 10.56.232.64 (External Network Number)
Link State ID: 10.56.232.68 (External Network Number)
Link State ID: 10.56.232.72 (External Network Number)
Link State ID: 10.56.232.96 (External Network Number)
Link State ID: 10.56.232.100 (External Network Number)
Link State ID: 10.56.232.104 (External Network Number)
Link State ID: 10.56.233.12 (External Network Number)
Link State ID: 10.56.233.16 (External Network Number)
Link State ID: 10.56.233.20 (External Network Number)
Alcatel PE# show router ospf database ext type external
===============================================================================
OSPF Link State Database (Type : External)
===============================================================================
Type Area Id Link State Id Adv Rtr Id Age Sequence Cksum
-------------------------------------------------------------------------------
AS Ext n/a 10.56.232.0 10.162.0.3 460 0x80000011 0x59fd
AS Ext n/a 10.56.232.32 10.162.0.3 460 0x80000012 0x7ab1
AS Ext n/a 10.56.232.64 10.162.0.3 460 0x80000011 0xd640
AS Ext n/a 10.56.232.68 10.162.0.3 460 0x80000011 0xae64
AS Ext n/a 10.56.232.72 10.162.0.3 460 0x80000011 0x8688
AS Ext n/a 10.56.232.96 10.162.0.3 460 0x80000011 0xf9f2
AS Ext n/a 10.56.232.100 10.162.0.3 460 0x80000011 0xd117
AS Ext n/a 10.56.232.104 10.162.0.3 460 0x80000011 0xa93b
AS Ext n/a 10.56.233.12 10.162.0.3 460 0x80000011 0xa194
AS Ext n/a 10.56.233.16 10.162.0.3 460 0x80000011 0x79b8
AS Ext n/a 10.56.233.20 10.162.0.3 460 0x80000011 0x51dc
Caution:
The "external-out enable" OSPF command should not be turned on without appropriate network planning.
Also it is important to note that the router takes "external-out" command without "enable" keyword under "router ospf". An operator can mistakenly type "ext" instead of “exit” to exit "router ospf config mode" and this can have the “external-out” command configured under "router ospf" unintentionally.
RP/0/RP0/CPU0:CORE#config
RP/0/RP0/CPU0:CORE(config)#router ospf 1
RP/0/RP0/CPU0:CORE(config-ospf)#external-out ?
disable Disable advertisement of intra-area routes as external
enable Enable advertisement of intra-area routes as external
<cr>
RP/0/RP0/CPU0:CORE(config-ospf)#ext
RP/0/RP0/CPU0:CORE(config-ospf)#show
router ospf 1
external-out enable
!