Lab 35 - OSPF Resource Management

Lab 35 - OSPF Resource Management
Di Posting Oleh : Simple Learning
Kategori : Core Technologies OSPF Routing

Prerequisites: CCNP level skills.

Personal Note!

A horrible tragedy happened in Japan today. Earthquake (8.8 on Richter scale) hit this country and sparked tsunami. It is a terrible event of cataclysmic proportions. 

My great sympathy to all who have suffered due to this unexpected calamity.

Note!
When OSPF summarizes prefixes (area range or summary-address) it installs a discard route in the routing table (pointing to NULL0). This is a loop prevention mechanism that prevents a router from sending the traffic to a network/subnet with a shorter match if no more specific route exists in the routing table.

Topology
 Pic. 1 - OSPF Topology.
Icons designed by: Andrzej Szoblik - http://www.newo.pl

Task 1
Use the configuration from the lab 34 (four loopbacks created).
  • Loopback 1: 10.0.0.1/24
  • Loopback 2: 10.0.1.1/24
  • Loopback 3: 10.0.2.1/24
  • Loopback 4: 10.0.1.1/24
Advertise these subnets in area 13 with their configured network mask.

Task 2
On R3 advertise the four loopbacks (1-4) as LSA5.

Task 3
Configure R3 so that it sends warning when the number of prefixes reaches 3 redistributed LSAs. But first warning should be sent when 60 percent of the threshold is reached. Check the results.

Task 4
Change the redistributed limit to 3 prefixes. If the number of prefixes redistributed into OSPF exceeds this number the excess should be rejected. Check the results.

Task 5
OSPF process on R1 should not exceed 15% to allow other process to operate. The maximum LSAs R1 can accept is 1500.

Lab Solution

Task 1
Use the configuration from the lab 34 (four loopbacks created).
  • Loopback 1: 10.0.0.1/24
  • Loopback 2: 10.0.1.1/24
  • Loopback 3: 10.0.2.1/24
  • Loopback 4: 10.0.1.1/24
Advertise these subnets in area 13 with their configured network mask.

R3 Configuration:
!
interface Loopback1
 ip address 10.0.0.1 255.255.255.0
!
interface Loopback2
 ip address 10.0.1.1 255.255.255.0
!
interface Loopback3
 ip address 10.0.2.1 255.255.255.0
!
interface Loopback4
 ip address 10.0.3.1 255.255.255.0
!

Task 2
On R3 advertise the four loopbacks (1-4) as LSA5.

R3 Configuration:
!
ip prefix-list LOOPBACKS seq 5 permit 10.0.0.0/22 le 24
!
route-map CONNECTED_TO_OSPF permit 10
 match ip address prefix-list LOOPBACKS
!
!

Verification:
All four subnets are showing in LDSB on R3 (show ip ospf database external).

Pic. 2 - R3's LSDB Content.
Task 3
Configure R3 so that it sends warning when the number of prefixes reaches 3 redistributed LSAs. But first warning should be sent when 60% of the threshold is reached. Check the results.

R3 Configuration:
!
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 redistribute maximum-prefix 3 60 warning-only
 redistribute connected subnets route-map CONNECTED_TO_OSPF
 network 10.1.13.3 0.0.0.0 area 13
 network 172.16.103.3 0.0.0.0 area 13
!

Note!
Entered a config and after a few seconds the following system messages were sent to console 0.

Verification:
Pic. 3 - System Logs.

Note!
The 'warning-only' keyword still allows more LSAs than the maximum threshold (here 3 LSA5).

Pic. 4 - R3's LSDB Has 4 LSA5.
Pic. 5 - R1's routing table.
Task 4
Change the redistributed limit to 3 prefixes. If the number of prefixes redistributed into OSPF exceeds this number the excess should be rejected. First warning should be sent when the maximum threshold of 3 reaches 60%. Check the results.

R3 Configuration:
!
router ospf 1
 router-id 3.3.3.3
 log-adjacency-changes
 redistribute maximum-prefix 3 60
 redistribute connected subnets route-map CONNECTED_TO_OSPF
 network 10.1.13.3 0.0.0.0 area 13
 network 172.16.103.3 0.0.0.0 area 13
!

Verification:
Pic. 6 - LSA Threshold Messages.

Note!
Only 3 LSAs Type5 are accepted by OSPF.

Pic. 7 - R3's LSDB Type-5.

Pic. 8 - R3 OSPF Output.
Task 5
OSPF process on R1 should not exceed 15% to allow other process to operate. The maximum LSAs R1 can accept is 1500.

R1 Configuration:
!
router ospf 1
 router-id 1.1.1.1
 log-adjacency-changes
 max-lsa 1500
 network 10.1.12.1 0.0.0.0 area 0
 network 10.1.13.1 0.0.0.0 area 13
 network 172.16.101.1 0.0.0.0 area 0
!

Verification:
Pic. 9 - Max LSA

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