DELL N3000 Manual De Usuario

Configuring OSPF and OSPFv3

exit

interface vlan 103

ip address 172.21.1.1 255.255.255.0

routing

ip ospf hello-interval 1

ip ospf dead-interval 4

ip ospf network point-to-point

exit

interface te1/0/21

switchport mode trunk

exit

interface loopback 0

ip address 172.21.254.2 255.255.255.255

exit

exit

With flood blocking disabled on all interfaces, sending a T3 summary LSA 

from R3 to R0 will cause R0 to forward the LSA on its interface to R1. 

Enabling flood blocking on R0's interface to R1 will inhibit this behavior. 

(R0)(config-if-vlan101)ip ospf database-filter all out

A trace on the R3-R0 link shows that the LSA is actually flooded from R1 to 

R0, since R1 received the LSA via R2. Even though R1 does not receive this 

LSA directly from R0, it still correctly computes the route through the R0:

(R1) #show ip route

console#show ip route

Route Codes: R - RIP Derived, O - OSPF Derived, C - Connected, S - Static

       B - BGP Derived, E - Externaly Derived, IA - OSPF Inter Area

       E1 - OSPF External Type 1, E2 - OSPF External Type 2

       N1 - OSPF NSSA External Type 1, N2 - OSPF NSSA External Type 2

O IA   100.0.0.0/24 [110/2] via 172.21.1.10,   00h:01m:35s,  0/25

OSPF also blocks external LSAs on the blocked interface. Stopping and 

restarting R3's OSPF protocol causes R3 to re-originate its router LSA. R0 

does not send R3's router LSA on the blocked interface.
With flood blocking enabled on the R0 interface, if the link from R0 to R1 

bounces, R0 Database Description packets do not include any LSAs. 

However, database synchronization still occurs (through R2) and R1 

computes the correct routes after the link is restored.