RE : Loopbacks in OSPF

From: Olivier Martin (omartin@xxxxxxxx)
Date: Sat Sep 15 2001 - 22:46:12 GMT-3


   
If you do a show ip ospf interface loopback0, here is a sample of what you
get :

Loopback1 is up, line protocol is up
  Internet Address 2.2.2.2/24, Area 0
  Process ID 1, Router ID 155.155.155.1, Network Type LOOPBACK, Cost: 1
  Loopback interface is treated as a stub Host

The key word is stub host. If you change the network type, using

int loopback1
 ip ospf network point-to-point

You will get :

Loopback1 is up, line protocol is up
  Internet Address 2.2.2.2/24, Area 0
  Process ID 1, Router ID 155.155.155.1, Network Type POINT_TO_POINT, Cost:
1
  Transmit Delay is 1 sec, State POINT_TO_POINT,
  Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5
    Hello due in 00:00:00
  Index 1/1, flood queue length 0
  Next 0x0(0)/0x0(0)
  Last flood scan length is 0, maximum is 0
  Last flood scan time is 0 msec, maximum is 0 msec
  Neighbor Count is 0, Adjacent neighbor count is 0
  Suppress hello for 0 neighbor(s)

This way, it's advertised as a /24 if the mask says so.

Hope this helps !

Olivier

-----Message d'origine-----
De : Przemyslaw Karwasiecki [mailto:karwas@ifxcorp.com]
Envoyi : 15 septembre, 2001 21:39
@ : ccielab@groupstudy.com
Objet : Loopbacks in OSPF

Hello,

Does anyone knows why loopbacks are always advertised in OSPF as /32? even
if they are defined as /24 or whatever different then /32

Is there any logical explanation for this phenomenon?

Thanks,

Przemek
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