From: Fred Ingham (fningham@xxxxxxxxxxxxxxxx)
Date: Mon Dec 18 2000 - 12:14:45 GMT-3
The reply by B. Arthayuth is right on the money. Physical and
multipoint frame relay interfaces are OSPF NBMA networks by default.
NBMA networks have a DR/BDR and in a hub and spoke
configuration the hub must be the DR. Neighbor statements are required
for NBMA.
You might ask yourself why the hub must be the DR?
Cheers, Fred.
Bill Young wrote:
>
> Fred (and others),
>
> Can someone refresh my memory as to why we need the neighbor statements in
> the FR OSPF config below?
>
> Thanks,
> Bill
>
> ----- Original Message -----
> From: "Fred Ingham" <fningham@worldnet.att.net>
> To: "Roy Grego" <ccsi100@yahoo.com>; <ccielab@groupstudy.com>
> Sent: Sunday, December 17, 2000 11:23 PM
> Subject: Re: Losing routes when OSPF red into IGRP
>
> > Long Answer.
> >
> > There are some general principles for redistributing VLSM-FLSM:
> > RIP will redistribute the 0.0.0.0 default network
> > use the default-information originate command
> > IGRP does not distribute the 0.0.0.0 network
> > use the ip default-network command
> > network must be classful, in routing table,
> > and not on FLSM router
> > Split horizon will effect routes
> > ip classless must be configured on the FLSM router.
> >
> > Sample config OSPF/RIP:
> > R1 - router running RIP and OSPF:
> >
> > int s0/0
> > encap frame
> > bandwidth 1000
> > !
> > int s 0/0.1 point-to-multipoint
> > description serial to r2 and r3
> > ip add 172.16.65.1 255.255.255.128 /25 will not be distributed
> > frame map ip 172.16.65.2 102 br to RIP or to IGRP
> > frame map ip 172.16.65 3 103 br
> > !
> > int s 0/0.2 point-to-point
> > description serial to r4
> > ip add 172.16.33.1 255.255.255.0 /24 in RIP or IGRP domain
> > frame-relay interface-dlci 102
> > !
> > router ospf 1
> > redistribute rip subnets
> > summary-address 172.16.44.0 255.255.252.0 r4 loopbacks
> > netw 172.16.65.0 0.0.0.255 area 0
> > neighbor 172.16.65.2 r1 is DR, this is
> > neighbor 172.16.65.3 another topic
> >
> > router rip
> > redistribute ospf 1 metric 3 Mutual redistribution
> > default-information originate distribute a default route
> > passive-interface s0/0.1
> > netw 172.16.0.0
> >
> > Note that route maps or distribute lists are not needed to
> > prevent loops. Why?
> >
> > R4 - router running RIP:
> >
> > int s 0
> > encap frame
> > ip add 172.16.33.4 255.255.255.0
> > frame map ip 172.16.33.1 401 br
> > ip split-horizon off by default, needs to be enabled
> > !
> > int loop 0
> > ip add 172.16.44.4 255.255.255.0
> > int loop 1
> > ip add 172.16.45.4 255.255.255.0
> > int loop 2
> > ip add 172.16.46.4 255.255.255.0
> > int loop 3
> > ip add 172.16.47.4 255.255.255.0
> > !
> > router rip
> > netw 172.16.0.0
> >
> > ip classless
> >
> > Discussion: r4 will announce and accept /24 routes. r4 will also
> > accept host, /32, routes, and classful routes. r1 will not advertise
> > /25 routes to r4. Without split horizon enabled r4 would announce
> > routes back to r1. With the default-information-originate there
> > will be a default route in r4's route table pointing to r1 s0/0.2.
> > The /25 routes will not be in r4's routing table but all interfaces
> > will be able to be pinged using the default route.
> >
> > r4 route table before default-information originate command:
> >
> > Gateway of last resort is not set
> >
> > 172.16.0.0/24 is subnetted, 5 subnets
> > C 172.16.44.0 is directly connected, Loopback44
> > C 172.16.45.0 is directly connected, Loopback45
> > C 172.16.46.0 is directly connected, Loopback46
> > C 172.16.47.0 is directly connected, Loopback47
> > C 172.16.33.0 is directly connected, Serial0
> >
> > r4 route table after adding default-information originate:
> >
> > Gateway of last resort is 172.16.33.1 to network 0.0.0.0
> >
> > 172.16.0.0/24 is subnetted, 5 subnets
> > C 172.16.44.0 is directly connected, Loopback44
> > C 172.16.45.0 is directly connected, Loopback45
> > C 172.16.46.0 is directly connected, Loopback46
> > C 172.16.47.0 is directly connected, Loopback47
> > C 172.16.33.0 is directly connected, Serial0
> > R* 0.0.0.0/0 [120/1] via 172.16.33.1, 00:01:18, Serial0
> >
> > ***********************************************************
> >
> > R1 - router running IGRP and OSPF (changes from above only):
> >
> > int e 0 another network which can be
> > ip address 192.168.1.1 255.255.255.0 from ospf or a connected interface
> > no keep on r1
> >
> > router ospf 1
> > no redistribute rip subnets
> > redistribute igrp 1 subnets
> >
> > no router rip
> >
> > router igrp 1
> > redistribute ospf 1
> > default-metric 1000 2000 255 1 1500
> > network 172.16.0.0
> > network 192.168.1.0 required since network is not in
> > passive-interface s0/0.1 ospf, could also redis connected
> >
> > ip default-network 192.168.1.0 classful, in r1's routing table,
> > not advertised by r4
> >
> > R4 - router running IGRP (changes only):
> >
> > no router rip
> >
> > router igrp 1
> > netw 172.16.0.0
> >
> > Discussion: Same comments as for RIP except now there
> > is no default 0.0.0.0 route. r4's routing table will have
> > a default gateway pointing to r1's s0/0.2. The /25 networks
> > will not be in the routing table but can be pinged using the
> > gateway of last resort. ip classless must be configured on r4.
> >
> > r4's routing table before ip default-network command:
> >
> > Gateway of last resort is not set
> >
> > 172.16.0.0/24 is subnetted, 5 subnets
> > C 172.16.44.0 is directly connected, Loopback44
> > C 172.16.45.0 is directly connected, Loopback45
> > C 172.16.46.0 is directly connected, Loopback46
> > C 172.16.47.0 is directly connected, Loopback47
> > C 172.16.33.0 is directly connected, Serial0
> >
> > r4's routing table after default network command:
> >
> > Gateway of last resort is 172.16.33.1 to network 192.168.1.0
> >
> > 172.16.0.0/24 is subnetted, 5 subnets
> > C 172.16.44.0 is directly connected, Loopback44
> > C 172.16.45.0 is directly connected, Loopback45
> > C 172.16.46.0 is directly connected, Loopback46
> > C 172.16.47.0 is directly connected, Loopback47
> > C 172.16.33.0 is directly connected, Serial0
> > I* 192.168.1.0/24 [100/8576] via 172.16.33.1, 00:00:05, Serial0
> >
> > HTH to clearify issues. Fred.
> >
> > Roy Grego wrote:
> > >
> > > Hello,
> > >
> > > When I red OSPF routes into IGRP I am losing some
> > > routes.
> > >
> > > Example:
> > >
> > > OSPF clouds -- R1 --- IGRP ----- R2
> > >
> > > R1 has these routes in its OSPF database & Routing
> > > table. R1 can ping all these addresses.
> > > C 1.1.1.1 /24
> > > E2 2.2.2.2 /30
> > > E2 3.3.3.3 /24
> > > C 4.4.4.4 /24
> > > O 5.5.5.5 /24
> > > O 6.6.6.6 /30
> > >
> > > BUT R2 will not see 3.3.3.3 or 6.6.6.6. Where do
> > > these go? The routes being lost are not all subnetted,
> > > nor are they External OSPF routes.
> > >
> > > Sample configs:
> > > router ospf 1
> > > network 1.1.1.1 0.0.0.0 area 0
> > > red igrp 4 subnets metric 500 route-map IGRP2OSPF
> > >
> > > router igrp 4
> > > network 4.0.0.0
> > > red ospf 1 match e i metric 1500 100 255 1 1500
> > >
> > > Is there a debug to see the routes being redistributed
> > > and/or routes rejected for redistribution?
> > >
> > > FYI, R1 has a Frame connection with Multipoint subint.
> > > and networks 3, 5, & 6 can be routed 2 different ways.
> > > Does OSPF have a problem with this?
> > >
> > > Thanks,
> > > ROY
> > >
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