From: Horace Chan (hcie@xxxxxxx)
Date: Wed Apr 11 2001 - 12:29:08 GMT-3
Hi
In refering to Routing TCP/IP Vol 1 by Jeff,
I am testing the lab scenario in page 223,
which consist of two routers.
I originally expect Router B will advertise 2 rip entry:
192.168.20.40
192.168.20.48
to Router A. Then, RouterA will imposing 27 bit subnet mask
as its local interface is configured as 27 bit sbunet mask.
So, the two route will be truncated to: 192.168.20.32/27
and will be ignored.
However, the actual lab testing is out of my expectation,
I find that router A have two rip learned route:
192.168.20.0/24 is variably subnetted, 5 subnets, 2 masks
C 192.168.20.64/27 is directly connected, Loopback30
R 192.168.20.48/32 [120/1] via 192.168.20.34, 00:00:21, Serial1
R 192.168.20.40/32 [120/1] via 192.168.20.34, 00:00:21, Serial1
C 192.168.20.32/27 is directly connected, Serial1
C 192.168.20.128/27 is directly connected, Loopback20
I really don't understand why RouterA will have the 2 32bit route. Can
anyone help?
I've tried to open the debug of:
ip rip
ip rip database
and get the following intesting message are as follow.
My friend also follow the lab config and get the same result. Is there
anything that we are missing?
=======================================================================
00:30:24: RIP: received v1 request from 192.168.20.34 on Serial1
0
00:30:24: RIP: sending v1 update to 192.168.20.34 via Serial1
(192.168.20.33) 0
00:30:24: RIP: build update entries
0
00:30:24: subnet 192.168.20.64 metric 1
0
00:30:24: subnet 192.168.20.128 metric 1
0
00:30:24: RIP: received v1 update from 192.168.20.34 on Serial1
0
00:30:24: 192.168.20.40 in 1 hops
0
00:30:24: RIP-DB: network_update with 192.168.20.40/24 succeeds
0
00:30:24: RIP-DB: adding 192.168.20.40/0 (metric 1) via 192.168.20.34 on
Serial1
to RIP database
0
00:30:24: RIP-DB: add 192.168.20.40/32 (metric 1) via 192.168.20.34 on
Serial1 0
00:30:24: 192.168.20.48 in 1 hops
0
00:30:24: RIP-DB: network_update with 192.168.20.48/24 succeeds
0
00:30:24: RIP-DB: adding 192.168.20.48/0 (metric 1) via 192.168.20.34 on
Serial1
to RIP database
0
00:30:24: RIP-DB: add 192.168.20.48/32 (metric 1) via 192.168.20.34 on
Serial1 0
00:30:25: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1, changed
stat
============================================================================
=
Router A config:
===========================
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname ra
!
boot system flash
logging buffered 65535 debugging
!
!
!
!
!
memory-size iomem 25
ip subnet-zero
no ip domain-lookup
!
!
!
!
process-max-time 200
!
interface Loopback20
ip address 192.168.20.129 255.255.255.224
no ip directed-broadcast
!
interface Loopback30
ip address 192.168.20.65 255.255.255.224
no ip directed-broadcast
!
interface Serial0
no ip address
no ip directed-broadcast
shutdown
!
!
interface Serial1
ip address 192.168.20.33 255.255.255.224
no ip directed-broadcast
!
interface Serial2
no ip address
no ip directed-broadcast
shutdown
!
interface Serial3
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet0
no ip address
no ip directed-broadcast
shutdown
!
router rip
passive-interface Loopback20
passive-interface Loopback30
network 192.168.20.0
!
ip classless
no ip http server
!
!
line con 0
transport input none
line aux 0
line vty 0 4
!
!
no scheduler allocate
end
===================
Router B Cofnig
=========================
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname rb
!
!
!
!
!
!
memory-size iomem 15
ip subnet-zero
no ip domain-lookup
!
!
!
!
interface Loopback20
ip address 192.168.20.49 255.255.255.248
no ip directed-broadcast
!
interface Loopback30
ip address 192.168.20.41 255.255.255.248
no ip directed-broadcast
!
interface Serial0
description S0 to RouterB
ip address 192.168.20.34 255.255.255.248
no ip directed-broadcast
no ip mroute-cache
clockrate 64000
!
interface Serial1
no ip address
no ip directed-broadcast
shutdown
!
interface Serial2
no ip address
no ip directed-broadcast
shutdown
!
interface Serial3
no ip address
no ip directed-broadcast
shutdown
!
interface FastEthernet0
no ip address
no ip directed-broadcast
shutdown
half-duplex
!
router rip
passive-interface Loopback20
passive-interface Loopback30
network 192.168.20.0
!
ip classless
no ip http server
!
!
line con 0
transport input none
line aux 0
line vty 0 4
login
!
end
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