Hi all,

I tried to use the "summary-address" OSPF command to summarize learned BGP
routes to a default summary route (0/0) and it seems that it doesn't work.

(fake BGP routes) ----- router A ------------ 1.0.0.0/32 (OSPF) ---------
router B


Router A :
--------------

router ospf 1
 log-adjacency-changes
 summary-address 0.0.0.0 0.0.0.0
 redistribute bgp 1 subnets
 network 1.0.0.0 0.255.255.255 area 0
!
router bgp 1
 bgp log-neighbor-changes
 network 5.0.0.0
 network 6.0.0.0
 network 7.0.0.0
 network 8.0.0.0
 network 9.0.0.0
 network 10.0.0.0
!
ip classless
ip route 5.0.0.0 255.0.0.0 Null0
ip route 6.0.0.0 255.0.0.0 Null0
ip route 7.0.0.0 255.0.0.0 Null0
ip route 8.0.0.0 255.0.0.0 Null0
ip route 9.0.0.0 255.0.0.0 Null0
ip route 10.0.0.0 255.0.0.0 FastEthernet0

Router B :
--------------

router ospf 1
 log-adjacency-changes
 network 1.0.0.0 0.255.255.255 area 0


On the router A, I can see that type 5 LSA is installed for 0/0 and
propagated to neighbor :

CustomerA#sh ip ospf database

       OSPF Router with ID (192.168.254.254) (Process ID 1)


                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
192.168.108.4   192.168.108.4   592         0x80000003 0x6121   2
192.168.254.254 192.168.254.254 592         0x80000006 0x7C72   2

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
0.0.0.0         192.168.254.254 4           0x80000001 0x2A22   0

But after some seconds, the external LSA is aged out and so disappears (by
what ????) :

CustomerA#sh ip ospf database

       OSPF Router with ID (192.168.254.254) (Process ID 1)


                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
192.168.108.4   192.168.108.4   593         0x80000003 0x6121   2
192.168.254.254 192.168.254.254 593         0x80000006 0x7C72   2

                Type-5 AS External Link States

Link ID         ADV Router      Age         Seq#       Checksum Tag
0.0.0.0         192.168.254.254 3600        0x80000002 0x301B   1

CustomerA#sh ip ospf database

       OSPF Router with ID (192.168.254.254) (Process ID 1)


                Router Link States (Area 0)

Link ID         ADV Router      Age         Seq#       Checksum Link count
192.168.108.4   192.168.108.4   597         0x80000003 0x6121   2
192.168.254.254 192.168.254.254 596         0x80000006 0x7C72   2


If I use another summary-address (like 4.0.0.0/6 or 8.0.0.0/5), it works
fine (external LSAs are not aged out).

Why this use doesn't work ?  What happens ? Why the LSA is aged out ?
The purpose of this test was to conditionnaly advertise default routes (if
BGP routes disappears, default route disappears).

NB : router A is 1750 router with IOS 12.1(14)

Thanks for help,


--
Stephane LITKOWSKI
Student in a French computer science school
EPITA Telecom & Network specialization
CCNA + CCNP
EMail : [EMAIL PROTECTED]




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