From: Carlos G Mendioroz (tron@xxxxxxxxxxx)
Date: Mon May 27 2002 - 09:33:06 GMT-3
It used to be the case that you didn't even need the unnumbered thing
(or the tunnel) to make this work.
OSPF would make adjacencies with ANY address in the other end of the
link.
It seems that now (12.x) it checks and rejects:
OSPF: Rcv pkt from 3.3.3.3, Serial1/1, area 0.0.0.0 : src not on the
same network
but I guess 11.3 still "works".
We had once a router with two links in an OSPF "ring" and somehow the
cables
to the DTUs got crossed. Everything kept running! We discover the issue
when trying to find the reason for a very strange traceroute...
Jason Sinclair wrote:
>
> All,
>
> As per RFC 2328:
>
> "9.5. Sending Hello packets Hello packets are sent out each functioning
> router interface. They are used to discover and maintain neighbor
> relationships.[6] On broadcast and NBMA networks, Hello Packets are also
> used to elect the Designated Router and Backup Designated Router. The format
> of an Hello packet is detailed in Section A.3.2. The Hello Packet contains
> the router's Router Priority (used in choosing the Designated Router), and
> the interval between Hello Packets sent out the interface (HelloInterval).
> The Hello Packet also indicates how often a neighbor must be heard from to
> remain active (RouterDeadInterval). Both HelloInterval and
> RouterDeadInterval must be the same for all routers attached to a common
> network. The Hello packet also contains the IP address mask of the attached
> network (Network Mask). On unnumbered point-to-point networks and on virtual
> links this field should be set to 0.0.0.0. "
>
> I think you may find this is why this works.
>
> Regards,
>
> Jason Sinclair CCIE #9100
> Manager, Network Control Centre
> POWERTEL
> Ground Level, 55 Clarence Street,
> SYDNEY NSW 2000
> AUSTRALIA
> office: + 61 2 8264 3820
> mobile: + 61 416 105 858
> * sinclairj@powertel.com.au
>
> -----Original Message-----
> From: Michael Snyder [mailto:msnyder@ldd.net]
> Sent: Monday, 27 May 2002 16:05
> To: 'mize'
> Cc: ccielab@groupstudy.com
> Subject: RE: This one will make your head hurt.
>
> And the Tunnel Interface has what subnet in common? They are on
> different Class A networks. I mean ospf has problems with
> discontinuous
> sub networks, never mind two different Class A networks. How would
> that
> hello packet work?
>
>
>
> -----Original Message-----
> From: mize [mailto:mize@netbuddy.org]
> Sent: Monday, May 27, 2002 12:46 AM
> To: Michael Snyder
> Cc: ccielab@groupstudy.com
> Subject: Re: This one will make your head hurt.
>
> Wonderful scenario but the reason is simple - OSPF in running on
> Tunnel
> 0 interface.
>
> ??
> >I'll let you figure it out. First take note that I can ping
> networks
> >1.1.1.1 and 3.3.3.3. Second notice that ospf has no subnets or
> >neighbors in common. None! Yet a full ospf database.
> >
> >
> >A#show run
> >Building configuration...
> >!
> >hostname A
> >!
> >interface Loopback0
> > ip address 1.1.1.1 255.255.255.0
> > ip ospf network point-to-point
> >!
> >interface Loopback1
> > ip address 2.2.2.2 255.255.255.0
> > ip ospf network point-to-point
> >!
> >interface Tunnel0
> > ip unnumbered Loopback1
> > tunnel source Loopback1
> > tunnel destination 4.4.4.4
> >!
> >interface Serial1
> > ip address 10.0.0.1 255.255.255.252
> > clockrate 56000
> >!
> >router ospf 80
> > log-adjacency-changes
> > network 1.1.1.0 0.0.0.255 area 1
> > network 2.2.2.0 0.0.0.255 area 0
> >!
> >ip route 4.4.4.0 255.255.255.0 Serial1
> >
> >A#si
> >
> >Gateway of last resort is not set
> >
> > 1.0.0.0/24 is subnetted, 1 subnets
> >C 1.1.1.0 is directly connected, Loopback0
> > 2.0.0.0/24 is subnetted, 1 subnets
> >C 2.2.2.0 is directly connected, Loopback1
> > 3.0.0.0/24 is subnetted, 1 subnets
> >O IA 3.3.3.0 [110/11112] via 4.4.4.4, 00:07:13, Tunnel0
> > 4.0.0.0/24 is subnetted, 1 subnets
> >S 4.4.4.0 is directly connected, Serial1
> > 10.0.0.0/30 is subnetted, 1 subnets
> >C 10.0.0.0 is directly connected, Serial1
> >A#p 3.3.3.3
> >
> >Type escape sequence to abort.
> >Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
> >!!!!!
> >Success rate is 100 percent (5/5), round-trip min/avg/max =
> 40/40/40 ms
> >A#show ip ospf n
> >
> >Neighbor ID Pri State Dead Time Address
> >Interface
> >4.4.4.4 1 FULL/ - 00:00:38 4.4.4.4
> >Tunnel0
> >A#show ip ospf d
> >
> > OSPF Router with ID (2.2.2.2) (Process ID 80)
> >
> >
> > Router Link States (Area 0)
> >
> >Link ID ADV Router Age Seq# Checksum
> Link
> >count
> >2.2.2.2 2.2.2.2 459 0x80000015 0xC28B 2
> >4.4.4.4 4.4.4.4 460 0x80000002 0x2A26 2
> >
> > Summary Net Link States (Area 0)
> >
> >Link ID ADV Router Age Seq# Checksum
> >1.1.1.0 2.2.2.2 496 0x80000001 0x33FD
> >3.3.3.0 4.4.4.4 455 0x80000002 0xAC75
> >
> > Router Link States (Area 1)
> >
> >Link ID ADV Router Age Seq# Checksum
> Link
> >count
> >2.2.2.2 2.2.2.2 233 0x80000004 0x77A3 1
> >
> > Summary Net Link States (Area 1)
> >
> >Link ID ADV Router Age Seq# Checksum
> >2.2.2.0 2.2.2.2 791 0x80000001 0xF1F
> >3.3.3.0 2.2.2.2 455 0x80000001 0x791F
> >4.4.4.0 2.2.2.2 455 0x80000001 0x5540
> >A#
> >
> >
> >
> >
> >
> >C#show run
> >Building configuration...
> >!
> >hostname C
> >!
> >!
> >!
> >interface Loopback0
> > ip address 3.3.3.3 255.255.255.0
> > ip ospf network point-to-point
> >!
> >interface Loopback1
> > ip address 4.4.4.4 255.255.255.0
> > ip ospf network point-to-point
> >!
> >interface Tunnel0
> > ip unnumbered Loopback1
> > tunnel source Loopback1
> > tunnel destination 2.2.2.2
> >!
> >interface Ethernet0
> > no ip address
> >!
> >interface Serial1
> > ip address 10.0.0.2 255.255.255.252
> >!
> >router ospf 80
> > log-adjacency-changes
> > network 3.3.3.0 0.0.0.255 area 2
> > network 4.4.4.0 0.0.0.255 area 0
> >!
> >ip classless
> >ip route 2.2.2.0 255.255.255.0 Serial1
> >!
> >end
> >
> >C#show ip route
> >Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B
> -
> BGP
> > D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter
> area
> > N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type
> 2
> > E1 - OSPF external type 1, E2 - OSPF external type 2, E -
> EGP
> > i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia -
> IS-IS
> >inter area
> > * - candidate default, U - per-user static route, o - ODR
> > P - periodic downloaded static route
> >
> >Gateway of last resort is not set
> >
> > 1.0.0.0 0xFFFFFF00 is subnetted, 1 subnets
> >O IA 1.1.1.0 [110/11112] via 2.2.2.2, 00:05:27, Tunnel0
> > 2.0.0.0 0xFFFFFF00 is subnetted, 1 subnets
> >S 2.2.2.0 is directly connected, Serial1
> > 3.0.0.0 0xFFFFFF00 is subnetted, 1 subnets
> >C 3.3.3.0 is directly connected, Loopback0
> > 4.0.0.0 0xFFFFFF00 is subnetted, 1 subnets
> >C 4.4.4.0 is directly connected, Loopback1
> > 10.0.0.0 0xFFFFFFFC is subnetted, 1 subnets
> >C 10.0.0.0 is directly connected, Serial1
> >C#p 1.1.1.1
> >
> >Type escape sequence to abort.
> >Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
> >!!!!!
> >Success rate is 100 percent (5/5), round-trip min/avg/max =
> 44/50/64 ms
> >C#show ip ospf nei
> >
> >Neighbor ID Pri State Dead Time Address
> >Interface
> >2.2.2.2 1 FULL/ - 00:00:37 2.2.2.2
> >Tunnel0
> >C#show ip ospf data
> >
> > OSPF Router with ID (4.4.4.4) (Process ID 80)
> >
> >
> > Router Link States (Area 0)
> >
> >Link ID ADV Router Age Seq# Checksum
> Link
> >count
> >2.2.2.2 2.2.2.2 367 0x80000015 0xC28B 2
> >4.4.4.4 4.4.4.4 367 0x80000002 0x2A26 2
> >
> > Summary Net Link States (Area 0)
> >
> >Link ID ADV Router Age Seq# Checksum
> >1.1.1.0 2.2.2.2 404 0x80000001 0x33FD
> >3.3.3.0 4.4.4.4 362 0x80000002 0xAC75
> >
> > Router Link States (Area 2)
> >
> >Link ID ADV Router Age Seq# Checksum
> Link
> >count
> >4.4.4.4 4.4.4.4 376 0x80000001 0x15F2 1
> >
> > Summary Net Link States (Area 2)
> >
> >Link ID ADV Router Age Seq# Checksum
> >1.1.1.0 4.4.4.4 356 0x80000001 0x8511
> >2.2.2.0 4.4.4.4 358 0x80000001 0x6132
> >4.4.4.0 4.4.4.4 368 0x80000001 0x8A95
> >C#
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