From: Ivan (ivan@iip.net)
Date: Mon May 14 2007 - 04:09:13 ART
suppress fa is used to manage Forward Addres in the OSPF LSA. This feature
can't converse type of route.
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
On Sunday 13 May 2007 17:32, Cagri Yucel wrote:
> I managed to solve this question but no idea how it works, I'll be glad if
> someone enlighten me on this issue
>
> R2
>
> R1 0 10 R4
>
> R3
>
> Sorry for dodgy diagram, R1 connected to R2 and R3. R4 connected to R2 and
> R3 and there is a link between R2 and R3.
> Area 10 is NSSA
> R4 redistribute one of its loopback
>
> Now, this route seems as N2 on R3 and E2 on R2 (depending who is doing the
> 7to5 conversion)
>
> Question asking to have it as N2 on both.
>
> When I put area 30 nssa translate type-7 suppress-fa
> on the router doing conversion I managed to achieve N2 on both routers.
>
> What is the idea behind ?
>
> Many thanks
This archive was generated by hypermail 2.1.4 : Fri Jun 01 2007 - 06:55:20 ART