From: ccie anees (ccieanees@yahoo.com)
Date: Thu Jan 04 2007 - 15:53:07 ART
Please take some time and look at this config
area 1 (NSSA) Area 0
R1 --------------------- R2 ------------------- R3
X.X.12.0/30 X.X.23.0/30
Step1:
######
R1:
redistribute Loopback0 (1.1.1.1)
Verify Result
##############
in R3:
show ip route will show
1.1.1.0/24 as E2 route.
X.X.12.0/30 as O IA route
************************************************************
Step2:
######
Suppress Area 1 route X.X.12.0/24 in Area 0
###########################################
R2:
router ospf 1
area 1 range X.X.12.0 255.255.255.0 no-advertise
Verify in R3:
show ip route
you will not see both the routes X.X.12.0/30 and 1.1.1.0/24
R3#show ip ospf database external
OSPF Router with ID (3.3.3.3) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 168
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 1.1.1.0 (External Network Number )
Advertising Router: 1.1.1.1
LS Seq Number: 80000001
Checksum: 0x38F0
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 1.1.12.1 <-----------------------------
External Route Tag: 0
Note:
you can see above that the forwarding address 1.1.12.1 for the redistributed
route 1.1.1.0.
And we filtered the X.X.12.0 from ABR (R2).
Because R3 does not have route to reach X.X.12.1, it can not populate 1.1.1.1
in R3 Routing table.
**********************************************************************************
Step3:
######
NSSA forwarding address suppression
###################################
R2:
router ospf 1
area 1 nssa translate type7 suppress-fa
Verify in R3
R3#show ip ospf database external
OSPF Router with ID (3.3.3.3) (Process ID 1)
Type-5 AS External Link States
Routing Bit Set on this LSA
LS age: 6
Options: (No TOS-capability, DC)
LS Type: AS External Link
Link State ID: 1.1.1.0 (External Network Number )
Advertising Router: 1.1.1.1
LS Seq Number: 80000002
Checksum: 0x61D6
Length: 36
Network Mask: /24
Metric Type: 2 (Larger than any link state path)
TOS: 0
Metric: 20
Forward Address: 0.0.0.0 <-----------------------------
External Route Tag: 0
Note: Now the forwarding address is 0.0.0.0 which is nothing but the
border-router. Now the router knows how to reach the border-router
which is X.X.23.2, it populates 1.1.1.0/24 in the routing table.
R3#show ip ospf border-routers
OSPF Process 1 internal Routing Table
Codes: i - Intra-area route, I - Inter-area route
i 2.2.2.2 [647] via 1.1.23.2, Serial1/2, ABR/ASBR, Area 3, SPF 117
**********************************************************************************
johngibson1541@yahoo.com wrote:
I am still looking into the nssa translated LSA forwarding address suppressing issue.
I am still in the dark. So exhausted in studying these days.
John
This archive was generated by hypermail 2.1.4 : Thu Feb 08 2007 - 23:46:55 ART