set on ABR:
area [area-number] default-cost [cost]
Sunday, 28 October 2012
OSPF Forwarding Address and How to Suppress It
If the forwarding address in an external LSA is specified, and this address is not reachable, the address contained in the LSA is not inserted into the route table. When NSSA ABR translates the type 7 NSSA LSA into they 5 LSA, by default the forwarding address is transferred from type 7 to type 5. The ABR can be configured to suppress the forwarding address during the translation, replacing the specified address with the address 0.0.0.0. When another router receives the type 5 external LSA with the forwarding address suppressed, instead of trying to direct traffic for the external address to the forwarding address the receiving router will attempt to direct the traffic to the toe 7 to type 5 translating ABR router.
area 10 nssa translate type 7 suppress-fa
Routing TCP/IP Volume 2, Second Edition
area range Command
area range command specifies the area to which the summary adress belongs, the summary address, and the address mask.
It also installs a route to the null interface automatically. The router can be configured to not install it in the route table using the command no discard-route.
no-advertise switch is used for filtering summary addresses to be advertise to backbone network.
Routing TCP/IP Volume 2, Second Edition
It also installs a route to the null interface automatically. The router can be configured to not install it in the route table using the command no discard-route.
no-advertise switch is used for filtering summary addresses to be advertise to backbone network.
Routing TCP/IP Volume 2, Second Edition
Which ABR Translates Type 7 to Type 5
In scenarios which there are more than one ABR connected to the NSSA area, only the ABR with the highest router-id may translate Type 7 LSA(s) to Type 5 LSA(s).
OSPF External Type 1 and Type 2 Comparison
E1 Routes: Both the external cost and internal OSPF cost matters.
E2 Routes: Only the external cost matters (unless there is a tie).
Use E2 if the goal is to always send traffic through one ASBR.
Use E1 if the goal is to balance the traffic, and make each router pick the closes ASBR.
CCNP-TSHOOT 642-902 Official Certification Guide
E2 Routes: Only the external cost matters (unless there is a tie).
Use E2 if the goal is to always send traffic through one ASBR.
Use E1 if the goal is to balance the traffic, and make each router pick the closes ASBR.
CCNP-TSHOOT 642-902 Official Certification Guide
Calculating the Cost of Type 2 External Routes-Inter-Area
- Calculate the cost to rech the ABR, based on the local area's topology.
- Add the cost from the ABR to the ASBR, as listed in a Type 4 LSA.
CCNP-ROUTE 642-902 Official Certification Guide
Calculating the Cost of Type 2 External Routes-Intra-Area
- Find the advertising ASBR(s) as listed in the Type 5 LSA(s).
- Calculate the lowest cost route to reach any of the ASBR(s) based on the area topology.
CCNP-ROUTE 642-902 Official Certification Guide
Subscribe to:
Posts (Atom)