01-23-2003 12:39 PM - edited 03-02-2019 04:28 AM
I have a network running RIP v2. When the network was originally built, it used IP unnumbered on serial links. The router at each end of the serial link has the serial interface (that uses IP unnumbered) and an ethernet interface that's in class C network in the 10.X.X.X network space. For example, Router A's ethernet interface might be 10.1.0.1/24 and Router B's ethernet interface might be 10.2.0.1/24. The ip unnumbered works perfectly.
Now I need to subnet the address space the the ethernet interface on Router A connects to. For example, I need to take the 10.1.0.0/24 space and subnet it into 10.1.0.0/25 and 10.1.0.128/25. I still want to run ip unnumbered across the serial links (there's a reason for this, honest. It's an unusual network.) Only problem is, now the subnet masks don't match on the ethernet interfaces at both ends of the link.
Can anyone tell me if this setup will still result in the ip unnumbered working across the serial links between Router A and Router B?
01-23-2003 01:00 PM
Take a look at this link: http://www.cisco.com/en/US/tech/tk648/tk365/technologies_tech_note09186a0080094e8d.shtml
Shouldn't be an issue.
Hope it helps.
Steve
01-23-2003 01:16 PM
yeah, I read this thing and it gave me heartburn. I think that my case is same major net, different subnets but even that is problematic. I figure the major net is the 10.0.0.0 network in my example. The subnets are the 10.1.0.0/24 and 10.2.0.0/24 subnets. In the example that Cisco gives for this, they show the same subnet mask on both networks. I have an old Cisco Press book (circa 1998) that makes a blanket statement that the subnet mask must be the same on both sides for ip unnumbered to work properly. It says this before it even discusses the cases given in the article you cited. After I further subnet one of my networks I no longer have masks of the same length so I'm wondering about this. Have you ever done what I'm asking about and had it work?
01-24-2003 01:33 AM
This post is interesting. The suggested link mentioned that:
"This document explains the concept of IP unnumbered, and provides several configuration examples for reference. "
So there could be several possible setup.
I haven't tried your setup but I think it will work since you are using RIP2 and I guess you have automatic summarization disabled.
Goodluck.
01-24-2003 12:22 PM
I put this together quickly in the lab and it worked (one side 10.1.0.0/16 and the other 10.2.0.0/24):
Router#sh run
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Router
!
boot system flash
!
ip subnet-zero
frame-relay switching
!
!
!
interface Loopback10
ip address 172.16.1.1 255.255.255.0
no ip directed-broadcast
!
interface Ethernet0
ip address 10.1.0.1 255.255.0.0
no ip directed-broadcast
!
interface Serial0
ip unnumbered Ethernet0
no ip directed-broadcast
clockrate 64000
!
interface Serial1
no ip address
no ip directed-broadcast
shutdown
!
router rip
version 2
network 10.0.0.0
network 172.16.0.0
!
ip classless
!
banner login ^C^C
banner motd ^Cefault
'^C
!
line con 0
transport input none
line aux 0
line vty 0 4
!
end
Router#
Router#sh ip rout
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, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.1.0 is directly connected, Loopback10
10.0.0.0/8 is variably subnetted, 4 subnets, 4 masks
R 10.2.0.0/24 [120/1] via 10.2.0.1, 00:00:26, Serial0
R 10.3.0.0/29 [120/1] via 10.2.0.1, 00:00:26, Serial0
R 10.0.0.0/8 [120/1] via 10.2.0.1, 00:00:26, Serial0
C 10.1.0.0/16 is directly connected, Ethernet0
R 192.168.1.0/24 [120/1] via 10.2.0.1, 00:00:26, Serial0
Router#
router2#sh run
Building configuration...
Current configuration:
!
version 12.0
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname router2
!
enable password cisco
!
ip subnet-zero
frame-relay switching
!
!
!
interface Loopback1
ip address 192.168.1.1 255.255.255.224
no ip directed-broadcast
!
interface Loopback2
ip address 10.3.0.1 255.255.255.248
no ip directed-broadcast
!
interface Ethernet0
ip address 10.2.0.1 255.255.255.0
no ip directed-broadcast
!
interface Serial0
ip unnumbered Ethernet0
no ip directed-broadcast
!
interface Serial1
no ip address
no ip directed-broadcast
shutdown
!
router rip
version 2
network 10.0.0.0
network 192.168.1.0
!
ip classless
!
!
line con 0
transport input none
line aux 0
line vty 0 4
login
!
end
router2#
router2#sh ip rout
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, * - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
R 172.16.0.0/16 [120/1] via 10.1.0.1, 00:00:09, Serial0
10.0.0.0/8 is variably subnetted, 4 subnets, 4 masks
C 10.2.0.0/24 is directly connected, Ethernet0
C 10.3.0.0/29 is directly connected, Loopback2
R 10.0.0.0/8 [120/1] via 10.1.0.1, 00:00:10, Serial0
R 10.1.0.0/16 [120/1] via 10.1.0.1, 00:00:10, Serial0
192.168.1.0/27 is subnetted, 1 subnets
C 192.168.1.0 is directly connected, Loopback1
router2#
Steve
01-28-2003 07:08 AM
Thanks Steve. Unfortunately I don't have a lab in which to try this kind of stuff out. (I'm hoping that will change). I appreciate the time you put into this.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide