manual neighbor configuration

gojericho0

Could someone give me a scenario where you would want to manually configure a neighbor when they are normally discovered through multicast?

I see that it changes the hellos to unicast when neighbors are manually, is the only reason to cut down on multicast traffic?

marlon23

You can be forced to do it on CCIE lab

gojericho0

This may be a little out of the scope of BSCI, but I was curious.

What about in non-broadcast networks such as frame-relay and for some reason its a full mesh or point-to-multipoint network? Pseudobroadcasts are performed, but they are processed swithed and have to do X amount of duplicate packets for X amount of links in the multipoint connection. This doesn't seem to scalable if there are numerous links.

I know the best choice is possible is to break the multipoint links into p2p links. If for whatever reason this is not viable solution would it be best to make the ospf network a nonbroadcast network and then configure the neighbors manually (Thinking this could be very tedious without a scripting mechanisim)?

Router(config-if)# ip ospf network broadcast

OR

Use Protocol Independent Multicast (PIM) to allow the traffic to be fast-switched and take less resources on the router?

Router(config-if)#  ip pim nbma-mode

marlon23

Hi again,

I have a scenario for you, when it is good to use it

Sometimes you can have neighbors on switched network (over VLAN f.e.), for example 1 with 10Mb ethernet, one with 100Mb FastEthernet and another one with 1Gb Ethernet. If your router has 100Mb interface he will assing the cost for OSPF based on this interface, however this is not correct cost to reach another neighbors (10Mb & 1Gb). Solution to this is to specify nonbroadcast OSPF network type there and use neighbor commands with cost option to fix traffic load balancing.

Another similar scenario could be frame-relay point-to-multipoint subinterface at hub and different CIRs at spokes, then you would also prefer to set up a point-to-multipoint nonbroadcast network type and set cost values based on CIR per neighbor.

So as you can see, if you care, you'll find a scenarios when specific ospf network type can solve some "issues".

networker050184

I'd just put the cost on the interface which would be much easier, but I guess if you are looking for a place to use the neighbor command it would do the trick...

gojericho0

Thanks guys, I appreciate it. Just trying to see the big picture with some of this stuff.

CiscoCerts

marlon23 wrote:

he will assing the cost

lol, sorry I couldn't help myself