Lab 28 – OSPF Stub Router Advertisement

Prerequisites: CCNP level skills.
Note!
Use the configuration from Lab6.
Topology
Pic. 1 – OSPF Topology.
Task 1
On R4 check the OSPF routing table. Also, check what cost R2 advertises towards 172.16.103.0/24 and 172.16.133.0/24.
Task 2
Configure routers so R2 advertises maximum metric for all prefixes except the ones that area originated by R2. Use one command to accomplish that.
Lab Solution

Task 1
On R4 check the OSPF routing table. Also, check what cost R2 advertises towards 172.16.103.0/24 and 172.16.133.0/24.
Pic. 2 – R4’s Routing Table.
Pic. 3 – 172.16.103.0/24 LSA Advertised by R2.

Task 2

Configure routers so R2 advertises maximum metric for all prefixes except the ones that area originated by R2. Use one command to accomplish that.

R2 OSPF Configuration:

!
router ospf 1
router-id 2.2.2.2
max-metric router-lsa
log-adjacency-changes
network 10.1.23.2 0.0.0.0 area 0
network 10.1.124.2 0.0.0.0 area 1
network 172.16.102.2 0.0.0.0 area 0
!

Verification:

Pic. 4 – R4’s Routing Table.
Notice!
R2‘s Loopback0 (originated by R2) is advertised with its original metric (1; Metric=2 because of the cost of R4 to reach R2).
Pic. 5 – R2’s LSA (172.16.102.0/24) with Original Cost.
Pic. 6 – 172.16.103.0/24 LSA Advertised by R2.
Note!
All LSAs (except for the originated one) R2 advertises with the maximu metric value 65536.

Note!
The ‘max-metric router-lsa’ command takes a few options. Without options (like in this post), R2 advertises max metric infinitely. If this cost should be advertised in a given time only (maintenance or other) the following options are available:
Pic. 7 – Options on-start.
Pic. 8 – Other Options.

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