From: Nick Shah (nshah@xxxxxxxxxxxxxx)
Date: Mon May 27 2002 - 03:47:00 GMT-3
basically, the same subnet/same mask rule is *over ruled* when using point
to point links & unnumbered interfaces... Check this out...
http://www.cisco.com/warp/public/104/ospfdb1.html
It is similar to the scenario you mentioned (using actual interfaces instead
of tunnel)
Nick
----- Original Message -----
From: "Michael Snyder" <msnyder@ldd.net>
To: "'mize'" <mize@netbuddy.org>
Cc: <ccielab@groupstudy.com>
Sent: Monday, May 27, 2002 4:04 PM
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.
>
> $B!!!!(B
> >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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