RE: Hub & Spoke, Multipoint, Nonbroadcast, Prefering one

From: Brian Dennis (bdennis@internetworkexpert.com)
Date: Sat Oct 04 2003 - 19:33:53 GMT-3


Have you tried OSPF point-to-multipoint non-broadcast? This is the exact
situation it was designed for. OSPF point-to-multipoint non-broadcast will
allow you to assign the cost based on the neighbor. Here is an example:

Rack1R4#sho run int s0/0
interface Serial0/0
 ip address 154.1.0.4 255.255.255.0
 encapsulation frame-relay
 ip ospf network point-to-multipoint non-broadcast
 frame-relay map ip 154.1.0.3 403 broadcast
 frame-relay map ip 154.1.0.5 405 broadcast
 no frame-relay inverse-arp
end

Rack1R4#sho ip os da ro 150.1.3.3

            OSPF Router with ID (150.1.4.4) (Process ID 1)

                Router Link States (Area 0)
  LS age: 386
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 150.1.3.3
  Advertising Router: 150.1.3.3
  LS Seq Number: 80000003
  Checksum: 0xD47D
  Length: 60
  Number of Links: 3

    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 150.1.0.0
     (Link Data) Network Mask: 255.255.255.0
      Number of TOS metrics: 0
       TOS 0 Metrics: 1
         
Rack1R4#sho ip os da ro 150.1.5.5

            OSPF Router with ID (150.1.4.4) (Process ID 1)

                Router Link States (Area 0)

  LS age: 406
  Options: (No TOS-capability, DC)
  LS Type: Router Links
  Link State ID: 150.1.5.5
  Advertising Router: 150.1.5.5
  LS Seq Number: 80000005
  Checksum: 0x1724
  Length: 72
  Number of Links: 4

    Link connected to: a Stub Network
     (Link ID) Network/subnet number: 150.1.0.0
     (Link Data) Network Mask: 255.255.255.0
      Number of TOS metrics: 0
       TOS 0 Metrics: 1

Rack1R4#

As you can see both 150.1.3.3 (154.1.0.3) and 150.1.5.5 (154.1.0.5) are
advertising the 150.1.0.0/24 network with an OSPF cost of 1. R4 is adding a
cost of 25 to the route from 154.1.0.5 and 50 to the route from 154.1.0.3.

Rack1R4#sho run | be router ospf
router ospf 1
 network 154.1.0.0 0.0.255.255 area 0
 neighbor 154.1.0.5 cost 25
 neighbor 154.1.0.3 cost 50

Rack1R4#sho ip route 150.1.0.0 255.255.255.0
Routing entry for 150.1.0.0/24
  Known via "ospf 1", distance 110, metric 26, type intra area
  Last update from 154.1.0.5 on Serial0/0, 00:06:13 ago
  Routing Descriptor Blocks:
  * 154.1.0.5, from 150.1.5.5, 00:06:13 ago, via Serial0/0
      Route metric is 26, traffic share count is 1
      ^^^^^^^^^^^^^^^^^^^

Brian Dennis, CCIE #2210 (R&S/ISP-Dial/Security)
bdennis@internetworkexpert.com
Toll Free: 877-224-8987
Direct: 775-745-6404 (Outside the US and Canada)
Internetwork Expert, Inc.
http://www.InternetworkExpert.com

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Michael Snyder
Sent: Saturday, October 04, 2003 1:55 PM
To: ccielab@groupstudy.com
Subject: Hub & Spoke, Multipoint, Nonbroadcast, Prefering one neighbor over
an other?

I got a simple hub and spoke lab I'm doing.

The requirement is that one downstream neighbor be preferred over
another that has equal cost routes to the same destination.

I know I could do this with a route-map, but it's not allowed.

It's using ospf, but I think the same problem apply with be with eigrp
too.

Can't change the cost or bandwidth or delay of one neighbor without
changing the other at the same time, because it's the same outgoing
interface.

Did I miss anything?

I've already tried changing the admin distance of just that one
neighbor. No luck, in fact the command seems broken.

The network type is non-broadcast, which means the ospf neighbor cost
command won't work either.

Assuming I did use a route-map. Would the set ip default next-hop get
it, or would I be better going all out with the set ip net-hop command?

Thanks in Advance,

Michael

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