05-09-2009 02:00 PM - edited 03-04-2019 04:42 AM
I have a router with lots of virtual interfaces. When one of the interfaces goes down every ospf route in the route table has its lifetime reset to zero.
I thought only the changed routes should change not all of them, am I right?
What would cause the whole route table to be recalculated and how do I stop it?
05-09-2009 03:23 PM
Dave,
OSPF is a link state protocol. All routers in a given area share the same information and if one link changes state, the SPF algorithm is ran on all routers and all routes for that area are reinstalled.
Regards
05-10-2009 01:04 AM
It appears only LSA type 1 cause the SPF algorithm to run.
Therefore, if the virtual-interfaces were redistributed into ospf instead of relying on the network statement I think it will stop SPF from running...
We see 33,000 SPF's!
05-10-2009 07:01 AM
Can you post the config?
05-10-2009 08:00 AM
Hi
The config for ospf is shown below. We have two router with the same config but only one is resetting every ospf route!
I suspect either an IOS bug or a 'feature' that makes 12.4 incompatible with 12.3 as that is the only difference I can see between both routers.
router ospf 1
log-adjacency-changes
redistribute connected subnets
redistribute static subnets
passive-interface default
no passive-interface GigabitEthernet0/0
no passive-interface GigabitEthernet0/1
network 10.144.224.0 0.0.31.255 area 0
network 10.105.0.0 0.0.31.255 area 0
default-information originate always
distribute-list 50 in
05-10-2009 11:52 AM
Hi Dave,
Using the network statement makes your virtual-access interfaces seen as intra-area links and so are announced as LSA type-1 to all the routers of the area.
As Harold said, receiving LSA type-1 is a trigger to run SPF algo as it means something changed in the topology (links added or removed)
Virtual-access interfaces are by definition not permanent links so each time they are created or deleted a LSA type 1 will be generated and SPF will be scheduled.
Changing the network statement to a redistribute configuration will stop the SPF iteration but you will have a lot of LSA type 5 generated instead. You should use the summary-address cmd to create an aggregated route:
http://www.cisco.com/en/US/docs/ios/iproute/command/reference/irp_osp3.html#wp1017123
HTH
Laurent.
05-10-2009 05:01 PM
Hi, Dave:
As was stated by two experts already, each router in an area must have an identical copy of the link state database. This allows each router to map out the area and create a logical view of the area network topology. When all the databases are synchronized and identical, the SPF algorithim is run to establish the most efficient route to each destination.
The link state database is populated by the link state advertisements that each OSPF neighbor floods to its neighbor. When there are point to point links within an area, the advertisements are categorized as LSA type 1, aka Router Link LSA, and they are sent to each neighbor. In an environment where the neighbors interfaces all belong to a broadcast network, a DR and BDR are elected, and then you have type 2 LSAs being exnchanged between the DROther Routers and the DR and BDR. These are known as network LSAs.
Getting back to your issue, your virtual interfaces (I'm assuming they are SVI vlan interfaces) are default OSPF Broadcast interfaces, but you are not establishing an OSPF neighborship with the vlan interfaces in the HSRP group, so its network type is inconsequential in this case. All interfaces are "passived-out", except for the gigabit interfaces (and Im assuming they are point-to-point links), which are creating neighborships and exchanging type-1 Router LSAs with the neighbor router.
If one of the virtual links goes down, the local router's database will now be altered, and thereby prompting the router to send send an LSU, Link State Update, to inform the neighbor router, who will in turn flood his neighbors, and so on and so forth, until all databases are once again synchronized. Once that happens, the SPF algorithim will be run again and a new RIB table derived.
Can you tell me exactly which "show" commands you are running and the output of each that is troubling you?
HTH
Victor
05-10-2009 11:17 PM
Hi
David has been helping me with this issue.
The virtual interfaces are (UK adsl) pppoA virtual-access interfaces. Whenever a connection
drops (or comes up) all routes in the ospf DB recalculate, we do not see this issue on any other LNS or router.
show ip route ospf will display something like this
O E2 192.168.0.1/32
[110/20] via 10.10.10.129, 00:01:48, GigabitEthernet0/0
[110/20] via 10.10.10.97, 00:01:48, GigabitEthernet0/1
I have changed the ospf network statement to include just the loopback/gig interfaces but this has not helped.
If I bounce a connection on a 7206 running 12.3 it does not recalc the whole DB
show ip route ospf will give the below
O E2 192.168.1.1/29
[110/20] via 10.10.10.132, 1d11h, GigabitEthernet0/3.999
[110/20] via 10.10.10.102, 1d11h, GigabitEthernet0/1.999
Of course the new routes will have a short time but the rest are ok.
Thanks
05-11-2009 06:45 AM
Hi Martin,
Are you sure on the other LNS, the IP unnumbered address is part of OSPF or just redistributed ?
Can you post the config of both LNS ?
Thanks
Laurent.
05-11-2009 08:06 AM
Hello
Working router (7206)
router ospf 1
log-adjacency-changes
redistribute connected subnets
redistribute static subnets
passive-interface default
no passive-interface GigabitEthernet0/1.999
no passive-interface GigabitEthernet0/3.999
network 192.168.224.0 0.0.31.255 area 0
network 10.10.0.0 0.0.31.255 area 0
default-information originate always
distribute-list 50 in
lc7206#sh ip ospf
Routing Process "ospf 1" with ID 192.168.0.254
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Minimum LSA interval 5 secs. Minimum LSA arrival 1 secs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 3182. Checksum Sum 0x6574033
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
External flood list length 0
Area BACKBONE(0)
Number of interfaces in this area is 1479 (5 loopback)
Area has no authentication
SPF algorithm last executed 1d19h ago
SPF algorithm executed 537 times
Area ranges are
Number of LSA 9. Checksum Sum 0x0483A3
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
broken router (7201)
router ospf 1
log-adjacency-changes
redistribute connected subnets
redistribute static subnets
passive-interface default
no passive-interface GigabitEthernet0/0
no passive-interface GigabitEthernet0/1
network 192.168.0.0 0.0.0.255 area 0
default-information originate always
distribute-list 50 in
tc7201#sh ip ospf
Routing Process "ospf 1" with ID 192.168.0.252
Supports only single TOS(TOS0) routes
Supports opaque LSA
Supports Link-local Signaling (LLS)
Supports area transit capability
It is an autonomous system boundary router
Redistributing External Routes from,
connected, includes subnets in redistribution
static, includes subnets in redistribution
Initial SPF schedule delay 5000 msecs
Minimum hold time between two consecutive SPFs 10000 msecs
Maximum wait time between two consecutive SPFs 10000 msecs
Incremental-SPF disabled
Minimum LSA interval 5 secs
Minimum LSA arrival 1000 msecs
LSA group pacing timer 240 secs
Interface flood pacing timer 33 msecs
Retransmission pacing timer 66 msecs
Number of external LSA 3185. Checksum Sum 0x659284A
Number of opaque AS LSA 0. Checksum Sum 0x000000
Number of DCbitless external and opaque AS LSA 0
Number of DoNotAge external and opaque AS LSA 0
Number of areas in this router is 1. 1 normal 0 stub 0 nssa
Number of areas transit capable is 0
External flood list length 1
Area BACKBONE(0)
Number of interfaces in this area is 730 (4 loopback)
Area has no authentication
SPF algorithm last executed 00:00:47.312 ago
SPF algorithm executed 34155 times
Area ranges are
Number of LSA 9. Checksum Sum 0x0483A3
Number of opaque link LSA 0. Checksum Sum 0x000000
Number of DCbitless LSA 0
Number of indication LSA 0
Number of DoNotAge LSA 0
Flood list length 0
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