From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Tue Oct 03 2006 - 03:19:49 ART
You are going to have a lot of odd problems depending on the order of operations as you are seeing. First off you show your routers as using the OSPF network type of non-broadcast but you do not have any OSPF neighbor statements in any of the routers. You should fix this first by adding the neighbor statements to R5 and clearing the OSPF processes on R1 and R2. Everything should work normal until you reboot R5 or R5's interface gets shutdown. ;-)
Remember that you are just trying to solve the symptoms of a problem (spokes not set to 0) that you created. There is way too much to learn in networking than to spend time looking at all of the thousands of odd symptions of problems we can create for ourselves. Granted a few are useful to know but far too many of them are not.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
________________________________________
From: Mengdi Cao [mailto:xianglingzj@gmail.com]
Sent: Monday, October 02, 2006 10:32 PM
To: Brian Dennis
Cc: Cisco certification
Subject: Re: Wired OSPF problem (IEWB lab 17)
Brain,
Thanks again and I believe a lot of person knows the rules here. But we need to understand why other than rules, especially when the rule does not work (please have a detailed look at my example).
The OSPF DR/BDR election process, in general, will always elect the router with highest priority as DR. But obviously in my example R5 with the highest priority is not elected. (Please note that R5 is never rebooted nor has interface went down. And by verifying the neighbour table it can be confirmed that R1 never form adjacency with R2 directly.)
And more over, once set both R1 and R2 priority to 0, R2-R5 neighbour relationship gone. Again this shows that there is some problem with this setting. We must find some ways to correct it.
On 10/3/06, Brian Dennis <bdennis@internetworkexpert.com> wrote:
As I said the spokes should have their priority set to 0 and here's why. If R5 is rebooted or R5's interface goes down, R1 and R2 could elect themselves DR since there isn't a DR on the segment, they can't see each other via OSPF hellos, and lastly because their priority isn't set to 0. When R5 comes back up, R5 sees that there already is a DR (R1 and/or R2) and since there already is a DR for the segment there isn't an election process no matter what R5's priority is set to. By setting the priority of spoke routers to 0 they will not participate in the DR/DBR election process and you will never have the problem of R1 or R2 becoming the DR.
Let me state this once more for the record ;-). In a true "hub and spoke" network, the spokes must NOT participate in the DR/BDR election process. This means that their OSPF priority must be set to 0.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
________________________________________
From: Mengdi Cao [mailto: xianglingzj@gmail.com]
Sent: Monday, October 02, 2006 8:22 PM
To: Brian Dennis
Cc: Cisco certification
Subject: Re: Wired OSPF problem (IEWB lab 17)
Hi, Dennis,
Thanks for your reply but it seems not for my questions. My questions, state it simple, is.
1. Is there anything which take higher priority than "priority" itself? (i.e. Why R1/R2 is elected DR though R5 got a higher priority?)
2.How will priority setting on one spoke of a P2MP network affect another spoke? ( i.e. Why R2 can not form adjacency once R1's priority is also set to 0?)
On 10/3/06, Brian Dennis <bdennis@internetworkexpert.com> wrote:
Short answer to this is that you need to set the OSPF proirity on the
spokes to 0 so that they do not participate in the DR/BDR election
process.This will ensure that the spokes never becoming DR or BDR.
HTH,
Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Mengdi Cao
Sent: Monday, October 02, 2006 9:14 AM
To: Cisco certification
Subject: Wired OSPF problem (IEWB lab 17)
Hi, Everyone,
Saw a really wired problem when I see this problem today in Lab17.
Briefly, R1, R2 and R5 connects through FR, with R5 having a P2MP
subinterface
R5 --- R1
|
R2
Interface configuration:
R1:
interface Serial0
ip address 173.1.125.1 255.255.255.0
encapsulation frame-relay
no fair-queue
frame-relay map ip 173.1.125.2 105
frame-relay map ip 173.1.125.5 105 broadcast
no frame-relay inverse-arp
R2:
interface Serial0
ip address 173.1.125.2 255.255.255.0
encapsulation frame-relay
no fair-queue
frame-relay map ip 173.1.125.1 205
frame-relay map ip 173.1.125.5 205 broadcast
no frame-relay inverse-arp
end
R5:
interface Serial0.125 multipoint
ip address 173.1.125.5 255.255.255.0
ip ospf network non-broadcast
ip ospf priority 10
frame-relay interface-dlci 501
frame-relay interface-dlci 502
end
OSPF is enabled on these interfaces with singel network statement
matching
the interface IP only.When the adjacency formed, it looks like:
Rack1R5#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
150.1.1.1 1 FULL/DROTHER00:01: 57173.1.125.1
Serial0.125
150.1.2.2 1 FULL/DR 00:01:54 173.1.125.2
Serial0.125
It seems that R2 is elected DR instead of R5, despite of the fact that
R5's
interface priority is 10, others are 1.
More wired things comes one when I revoked the eligibility of being a
DR/BDR:
Rack1R2#conf t
Enter configuration commands, one per line.End with CNTL/Z.
Rack1R2(config)#int s0
Rack1R2(config-if)#ip ospf pri 0
Rack1R2(config-if)#^Z
Rack1R2#
Now it's R1's turn to be DR:
Rack1R5#clear ip ospf pro
Reset ALL OSPF processes? [no]: y
Rack1R5#
*Mar1 02:21:21.791: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.1.1 on
Serial0.125 from FULL to DOWN, Neighbor Down: Interface down or detached
*Mar1 02:21:21.799: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.2.2 on
Serial0.125 from 2WAY to DOWN, Neighbor Down: Interface down or detached
Rack1R5#
*Mar1 02:23:27.087: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.1.1 on
Serial0.125 from LOADING to FULL, Loading Done
Rack1R5#
*Mar1 02:23:32.043: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.2.2 on
Serial0.125 from LOADING to FULL, Loading Done
Rack1R5#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
150.1.1.1 1 FULL/DR 00:01:58173.1.125.1
Serial0.125
150.1.2.2 0 FULL/DROTHER00:01: 50173.1.125.2
Serial0.125
As R5 has to be DR for P2MP network, I further revoked R1's eligibility:
Rack1R1#conf t
Enter configuration commands, one per line.End with CNTL/Z.
Rack1R1(config)#int s0
Rack1R1(config-if)#ip ospf pri 0
Rack1R1(config-if)#^Z
Rack1R1#^Z
Then the thing comes to an end, R5-R2 neighbour relationship is gone
after I
clear the ospf processs!!
Rack1R5#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
150.1.1.1 0 FULL/DROTHER00:01:56 173.1.125.1
Serial0.125
Rack1R5#clear ip ospf prot
^
% Invalid input detected at '^' marker.
Rack1R5#clear ip ospf proc
Reset ALL OSPF processes? [no]: y
Rack1R5#
*Mar1 03:57:10.795: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.1.1 on
Serial0.125 from 2WAY to DOWN, Neighbor Down: Interface down or detached
Rack1R5#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
150.1.1.1 0 FULL/DROTHER00:01: 59173.1.125.1
Serial0.125
Rack1R5#
*Mar1 03:59:16.167: %OSPF-5-ADJCHG: Process 1, Nbr 150.1.1.1 on
Serial0.125 from LOADING to FULL, Loading Done
Rack1R5#
Rack1R5#sh ip ospf nei
Neighbor ID Pri State Dead Time Address
Interface
150.1.1.1 0 FULL/DROTHER00:01:58173.1.125.1
Serial0.125
I checked the output of show ip ospf interface command, nothing found:
Rack1R1#sh ip ospf int s0
Serial0 is up, line protocol is up
Internet Address 173.1.125.1/24, Area 0.0.0.0
Process ID 1, Router ID 150.1.1.1, Network Type NON_BROADCAST, Cost:
64
Transmit Delay is 1 sec, State DROTHER, Priority 0
Designated Router (ID) 150.1.5.5, Interface address 173.1.125.5
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:20
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 4
Last flood scan time is 4 msec, maximum is 4 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 150.1.5.5(Designated Router)
Suppress hello for 0 neighbor(s)
Rack1R2#sh ip ospf int s0
Serial0 is up, line protocol is up
Internet Address 173.1.125.2/24, Area 0.0.0.0
Process ID 1, Router ID 150.1.2.2, Network Type NON_BROADCAST, Cost:
64
Transmit Delay is 1 sec, State DROTHER, Priority 0
No designated router on this network
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:11
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 3
Last flood scan time is 0 msec, maximum is 4 msec
Neighbor Count is 0, Adjacent neighbor count is 0
Suppress hello for 0 neighbor(s)
Rack1R5#sh ip ospf int s0.125
Serial0.125 is up, line protocol is up
Internet Address 173.1.125.5/24, Area 0.0.0.0
Process ID 1, Router ID 150.1.5.5, Network Type NON_BROADCAST, Cost:
64
Transmit Delay is 1 sec, State DR, Priority 255
Designated Router (ID) 150.1.5.5, Interface address 173.1.125.5
No backup designated router on this network
Timer intervals configured, Hello 30, Dead 120, Wait 120, Retransmit 5
oob-resync timeout 120
Hello due in 00:00:24
Index 1/1, flood queue length 0
Next 0x0(0)/0x0(0)
Last flood scan length is 1, maximum is 8
Last flood scan time is 0 msec, maximum is 8 msec
Neighbor Count is 1, Adjacent neighbor count is 1
Adjacent with neighbor 150.1.1.1
Suppress hello for 0 neighbor(s)
Rack1R5#
Reviewed my final OSPF configuration, it seems also OK:
Rack1R1#sh run | b router ospf
router ospf 1
router-id 150.1.1.1
log-adjacency-changes
network 150.1.1.1 0.0.0.0 area 0.0.0.0
network 173.1.13.1 0.0.0.0 area 0.0.0.0
network 173.1.125.1 0.0.0.0 area 0.0.0.0
network 173.1.137.1 0.0.0.0 area 0.0.0.137
!
Rack1R2#sh run | b router osp
router ospf 1
router-id 150.1.2.2
log-adjacency-changes
area 0.0.0.23 nssa
network 150.1.2.2 0.0.0.0 area 0.0.0.0
network 173.1.23.2 0.0.0.0 area 0.0.0.23
network 173.1.32.2 0.0.0.0 area 0.0.0.0
network 173.1.125.2 0.0.0.0 area 0.0.0.0
!
Rack1R5#sh run | b router ospf 1
router ospf 1
router-id 150.1.5.5
log-adjacency-changes
redistribute eigrp 10 metric-type 1 subnets
network 150.1.5.5 0.0.0.0 area 0.0.0.0
network 173.1.125.5 0.0.0.0 area 0.0.0.0
!
Anybody got some hint on what is really happening?And how to correct
this?Thanks a lot!!
This archive was generated by hypermail 2.1.4 : Wed Nov 01 2006 - 07:29:04 ART