03-05-2008 01:46 AM - edited 03-03-2019 08:58 PM
Hi,I have an OSPF network setup - loopback on 1 router is configured with a /24 mask rather than with /32.This network has been added to the OSPF routing table with a /24 mask even though in the OSPF process on the router I have given it a /32 mask. Any idea how I can force the routing process to inject the route into the routing table with a /32 only. Please note that this is just a lab exercise?
Regards
Mary
Solved! Go to Solution.
03-05-2008 02:26 AM
there are 3 ways to sort it out,
summary addresses, redistribution and er look at groupstudy
03-05-2008 02:10 AM
Hello,
Do you have "ip ospf network point-to-point" command configured under the loopback?
Please have a look at the OSPF FAQ (Why are loopbacks advertised as /32 host routes in OSPF?):
http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml#qone
Kind Regards,
M.
03-05-2008 02:16 AM
Yeah, I do have ip ospf network point-to-point configured under the loopback but its still not working and appearing as /24 in the next-hop router
03-05-2008 02:20 AM
Hello,
I meant that you should try to remove this command :-)
Kind Regards,
Maria
03-05-2008 02:26 AM
there are 3 ways to sort it out,
summary addresses, redistribution and er look at groupstudy
03-05-2008 02:27 AM
Ok grand, ta, will have a look
03-05-2008 06:30 AM
Mary
OSPF treats a loopback interface as a stub host; i.e whatever (address, mask) pair is configured, the address of the loopback
interface will be advertised as a host route to the neighbors and hence you will not be required to do any summarization
The routing table on the originating router would be shown as a /24 as a connected route
HTH
Narayan
03-05-2008 09:22 AM
Mary,
The "ip ospf network point-to-point" command under your Loopback interface is what causes the network NOT to be advertised as a host route. If this command is missing, then the network will be advertised as a host route to other routers (default behavior). Only the router with the particular loopback will see the route as a connected /24 (the ways to get rid of connected routes are pretty violent and I think this is not what you want). Isn't the /24 in other routers what you are trying to get rid of? If it is, then you could try to remove the "ip ospf network point-to-point" command by preceeding it with a "no" or try to configure some other ospf network type (such as broadcast or multipoint).
Redistribution of connected subnets will not manage to advertise a /32. The external route that will result from redistribution, will be covering the /24 under the Loopback interface.
Kind Regards,
M.
p.s. Those labs are very realistic as always. The simplest thing to do in normal life is to have /32 masks on loopbacks :-)
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