CCNP - ospf->point-to-multipoint->cost

Author

ospf->point-to-multipoint->cost

2000-12-21, 8:00 am

http://www.cisco.com/univercd/cc/td...m#xtocid1794723

"On point-to-multipoint, broadcast networks, you can use the neighbor command and you MUST specify a COST to that neighbor.

(...)

interface Serial0
ip address 10.0.1.1 255.255.255.0
encapsulation frame-relay
IP OSPF COST 100
ip ospf network POINT-TO-MULTIPOINT
frame-relay map ip 10.0.1.3 202 broadcast
frame-relay map ip 10.0.1.4 203 broadcast
frame-relay map ip 10.0.1.5 204 broadcast
frame-relay local-dlci 200
!
router ospf 1
network 10.0.1.0 0.0.0.255 area 0
neighbor 10.0.1.5 COST 5
neighbor 10.0.1.4 COST 10

COMMENTS
- "IP OSPF COST" is declared
- a COST is not assigned to neighbor "10.0.1.3"

QUESTION
- is it necessary to declare the cost of the interface ("ip ospf cost")?
- why is it necessary to define the cost on point-to-multipoint broadcast? and why NOT on non-broadcast?
- can you confirm that a cost to neighbor 10.0.1.3 should be assigned as well.

thanks for your comments
frans

2000-12-21, 3:43 pm

quote:
Originally posted by emo francois:
QUESTION
1. is it necessary to declare the cost of the interface ("ip ospf cost")?
2. why is it necessary to define the cost on point-to-multipoint broadcast? and why NOT on non-broadcast?
3. can you confirm that a cost to neighbor 10.0.1.3 should be assigned as well.

Here's my take on this:

1. No. If you don't declare it explicitly, it will be computed from the bandwidth (default or explicit) for that interface.

2. I don't know.

3. No, I cannot. I think the cost to 10.0.1.3 will be the cost of using the interface (100).

Cheers!

2000-12-22, 6:44 am

you are right as i discovered later at the same url:

"Otherwise, neighbors will assume the cost of the interface, based on the ip ospf cost command."

thanks to you
frans

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