Re: OSPF discontiguous areas

From: Rick Mur <rmur_at_ipexpert.com>
Date: Sat, 5 Sep 2009 17:44:18 +0200

Can you explain why you thought it initially wouldn't work? Since the
area 0 in the middle with other areas around it is exactly how OSPF is
designed in the first place :-)

-- 
Regards,
Rick Mur
CCIE2 #21946 (R&S / Service Provider)
Sr. Support Engineer  IPexpert, Inc.
URL: http://www.IPexpert.com
On 5 sep 2009, at 15:28, Molomo wrote:
> Andy,
>
> We labbed it, it actually does work... it means they are different  
> areas
> then.
>
> Thanks  Andy...
>
>
>
>
> On Sat, Sep 5, 2009 at 2:22 PM, Andy Reid <ccie_at_reid.it> wrote:
>
>> Hi Molomo,
>>
>> Yes that will work just fine.
>> You can lab it yourself with just 3 routers:
>>
>> R2----area 1---R5---area 0 (loopback 0)---area 1-----R4
>>
>> I took a break out of the exciting world of multicast to lab it  
>> myself:
>>
>> R2:
>> interface Loopback0
>> ip address 2.2.2.2 255.0.0.0
>> !
>> interface Serial0/0
>> no ip address
>> encapsulation frame-relay
>> no dce-terminal-timing-enable
>> !
>> interface Serial0/0.25 point-to-point
>> ip address 10.1.25.2 255.255.255.0
>> ip pim sparse-mode
>> frame-relay interface-dlci 205
>> !
>> router ospf 1
>> log-adjacency-changes
>> network 0.0.0.0 255.255.255.255 area 1
>> end
>>
>> R5:
>> interface Loopback0
>> ip address 5.5.5.5 255.0.0.0
>> !
>> interface Serial0/0
>> no ip address
>> encapsulation frame-relay
>> !
>> interface Serial0/0.52 point-to-point
>> ip address 10.1.25.5 255.255.255.0
>> ip pim sparse-mode
>> frame-relay interface-dlci 502  !
>> !
>> interface Serial0/0.54 point-to-point
>> ip address 10.1.45.5 255.255.255.0
>> ip pim sparse-mode
>> frame-relay interface-dlci 504  !
>> router ospf 1
>> log-adjacency-changes
>> network 5.5.5.5 0.0.0.0 area 0
>> network 10.0.0.0 0.255.255.255 area 1
>> end
>>
>> R4:
>> interface Loopback0
>> ip address 4.4.4.4 255.0.0.0
>> !
>> interface Serial0/0
>> no ip address
>> encapsulation frame-relay
>> no dce-terminal-timing-enable
>> !
>> interface Serial0/0.45 point-to-point
>> ip address 10.1.45.4 255.255.255.0
>> ip pim sparse-mode
>> frame-relay interface-dlci 405  !
>> router ospf 1
>> log-adjacency-changes
>> network 0.0.0.0 255.255.255.255 area 1
>> end
>>
>> The end result is area 0 on a stick :)
>>
>> R5#show ip os ne
>> Neighbor ID     Pri   State           Dead Time   Address          
>> Interface
>> 4.4.4.4           0   FULL/  -        00:00:32    10.1.45.4
>> Serial0/0.54
>> 2.2.2.2           0   FULL/  -        00:00:37    10.1.25.2
>> Serial0/0.52
>>
>> R5#show ip route ospf
>>   2.0.0.0/32 is subnetted, 1 subnets
>> O       2.2.2.2 [110/65] via 10.1.25.2, 00:07:09, Serial0/0.52
>>   4.0.0.0/32 is subnetted, 1 subnets
>> O       4.4.4.4 [110/65] via 10.1.45.4, 00:07:09, Serial0/0.54
>>
>>
>> R2#show ip route ospf
>>   4.0.0.0/32 is subnetted, 1 subnets
>> O       4.4.4.4 [110/129] via 10.1.25.5, 00:07:38, Serial0/0.25
>>   5.0.0.0/32 is subnetted, 1 subnets
>> O IA    5.5.5.5 [110/65] via 10.1.25.5, 00:07:38, Serial0/0.25
>>   10.0.0.0/24 is subnetted, 2 subnets
>> O       10.1.45.0 [110/128] via 10.1.25.5, 00:07:38, Serial0/0.25
>>
>> R2#ping 4.4.4.4
>> Type escape sequence to abort.
>> Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds:
>> !!!!!
>> Success rate is 100 percent (5/5), round-trip min/avg/max =  
>> 112/127/176 ms
>>
>> R4#show ip route ospf
>>   2.0.0.0/32 is subnetted, 1 subnets
>> O       2.2.2.2 [110/129] via 10.1.45.5, 00:08:18, Serial0/0.45
>>   5.0.0.0/32 is subnetted, 1 subnets
>> O IA    5.5.5.5 [110/65] via 10.1.45.5, 00:08:18, Serial0/0.45
>>   10.0.0.0/24 is subnetted, 2 subnets
>> O       10.1.25.0 [110/128] via 10.1.45.5, 00:08:18, Serial0/0.45
>>
>> Also check out this Cisco link:
>> http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml
>>
>> regards Andy
>>
>>
>> Molomo wrote:
>>
>>> Experts,
>>>
>>> I would like to know if the setup below is valid, and whether R1 &  
>>> R4 will
>>> be able to reach each other.
>>>
>>>
>>> R1---area 1-----R2---area 0-----R3----area 1-----R4
>>>
>>>
>>> Regards,
>>> Molomo
>>>
>>>
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>>>
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>
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Received on Sat Sep 05 2009 - 17:44:18 ART

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