Mark, It sounds like you want to create a huge subnet that spans across 3 links? If you are trying to have both the ethernet interface and the serial interface be unnumbered to the loopback interface you would inherintly introduce a problem to the router. The problem would be with the internal logic of a router running IP (if in fact it is routing). Let's take this scenario as an example. You are the router and you receive a packet destined for 192.168.10.5 which interface do you shoot it out of if the serial interface is addressed 192.168.10.1 255.255.255.0 and the ethernet interface is addressed 192.168.10.1 255.255.255.0, and you don't have any more specific static routes? You are now telling the router the 192.168.10.0/24 subnet is over here, and also saying the 192.168.10.0/24 subnet is over here. I don't see the reasoning in why you would want to try something like this, especially when you are using private addresses. Why not address the ethernet interface seperately and then possibly use the unnumbered loopback 0 on the serial interface? If you want everything to be on the same subnet you could just bridge everything. I am quite familiar with IP, but not such an old head to know all of the inner workings of DECnet. The DECnet concept of basically using a node address instead of addressing each interface kindof goes along with this type of setup you are trying by kindof establishing the loopback interface as the node address. IP was designed to have each interface addressed. In IP as I'm sure you know the mask portion of an IP address defines which hosts reside on this link. By default in your setup there will be 2 connected routes pointing packets destined for the 192.168.10.0/24 subnet to the serial and the ethernet interfaces. If you add more specific routes to it would fix that issue of not knowing which interface to push packets out of since those routes would be more preferred, but I believe these more specific routes would have to be manually entered, because a routing protocol will simply advertise the addressed networks (RIP, IGRP) or subnets (EIGRP, IS-IS, OSPF, BGP), not specific host routes.
Crazy idea, Good luck with it and please let us know how it works out for you. >>>Brian ""Mark Odette II"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > OK, I'll make the question simpler. > > > Can you use a loopback interface in the same respect that you would use an > ethernet interface? > > Create the loopback: Interface Loopback0 > Assign it an IP with a /24 mask : ip address 192.168.10.1 > Configure the subnet assigned to the loopback interface to a routing > process, such as EIGRP or RIP. > Assign many other hosts on a LAN or a WAN an IP address that is in the same > subnet as the loopback interface. > Replicate the above configuration on Router at other end of FR network. > add subnet assigned to far-end routers' loopback interface to local EIGRP > AS, or RIP; do the same on the far-end routers' config for the same EIGRP AS > or RIP configuration. > > And then, configure FR Subinterface with IP Unnumbered Loopback0, and route > traffic across the FR network, with the traffic orininating from either the > Router, or another host (if configuration above is legal) on the subnet that > is assigned to the Loopback interface. > > What I want to do, is configure a VoIP enabled router with a loopback > interface assigned to 192.168.10.1, and several LAN hosts with the same > subnet assignment, i.e., 192.168.10.2, .3, .4, etc., and a /24 subnet mask > for all hosts including loopback interface. > I then want to create and assign IP Unnumbered loopbackX to a FR P-to-P > subinterface. > > Create EIGRP AS to route Subnets assigned to loopback interfaces on each > respective router. > > Mirror image this configuration on the other end of the "wire" (FR Network). > > Configure Dial-Peers with VOIP destinations pointing to the loopback > interface of the peer router (other end of the FR Network). > > Is this Possible?? > > > The reason why I want to use Loopback interfaces, is because I plan to > assign a separate subnet to the FastEthernet Interface, and don't believe > that the use of the Secondary command will work, i.e., you can't specify IP > Unnumbered FastEthernet0 and have the Secondary IP address used.... ip > unnumbered fastethernet0 will use the FastEthernets' Primary address, which > is not desired. > > The Primary Subnet assigned to the FastEthernet Interface will be NAT > Translating with a PIX FW (PIX will be doing the NAT) to hit the Internet. > > > For Topology description: > Router HQ connects to internet on one subinterface, while connecting to 3 > remote offices on a private FR network on a second subinterface. > Router Remote1 Will be connecting to the internet on one subinterface, while > connecting back to HQ on separate FR subinterface for VoIP over FR traffic > only (no Data traffic) > Router Remote2 will be doing the same as Remote1 > Router Remote3 will also be doing the same as Remote1 > > ... So much for a simpler reply. :) > > Thanks in advance for everyones' comments. > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of > Tshon > Sent: Tuesday, March 12, 2002 11:44 PM > To: [EMAIL PROTECTED] > Subject: Re: Loopback Interfaces... [7:37933] > > > What in the world is the question about, what are you trying to do. > Ping the remote routers, they have a serial > interface that you can ping, or the ethernet. Why do you need a > loopback, what routing protocol are you > running, where is a config? We can't figure out what you are talking > about, we need your help to help you. > > Brian Lodwick wrote: > > >This has got to be the most confusing message I have ever read. > >A loopback interface is just a virtual interface. It's not a real interface > >it's just a virtual interface you can create within the router, and you can > >create as many as you want. > >The biggest reason someone would want to use a loopback interface would be > >for resiliency. If you build a certain session to the loopback interface > >(BGP, DLSW...) and you have more than one path to reach this router the > >session will not die if a certain interface dies. > > ___________ ( ) > >------- r1 >>Brian > > > > > >""Mark Odette II"" wrote in message > >[EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > >>Just when I thought I understood Loopback interfaces, I decided while > >>redesigning a network, that I would use them.... but now I'm questioning > >> > >my > > > >>comprehension. > >> > >>Somebody clear the confusion for me- Please. > >> > >> > >>This is what I'm wanting to do, but not sure if this is proper > >> > >utilization, > > > >>much less whether or not it will work: > >> > >> > >> > >>RouterHQ connecting to 3 Remote Routers (branch offices) via FR Pvt > >> > >Network > > > >>RouterHQ has 2 Ethernet Interfaces, but the Remotes Do NOT....They only > >> > >have > > > >>one. > >>(I think without pause: "No Problem, I can just create a Loopback > >> > >interface > > > >>to take care of the other subnet.") > >> > >>The FR Pvt Network is only for Voice Traffic, while all data traffice will > >>be going out another interface that is using IP UnNumbered Interface > >>FastEthernet0. > >> > >>Here is where my quandry lays. I can't create a Secondary address, as I > >>believe the IP UnNumbered command will use the primary address on the > >>Ethernet Interface. > >> > >>So, can I create a Loopback interface, and treate it like a Ethernet > >>interface, as such that I can assign an IP to the Loopback interface, but > >> > >it > > > >>have a /24 mask, and other devices on the local network can also be keyed > >>for the same subnet as the Loopback, making it where I can give the > >> > >command > > > >>IP UnNumbered Lo0 to a Serial SubInterface?? > >> > >>I thought I could, but then got concerned when I hopped on CCO, and did a > >>lookup on Loopback interfaces, and read a blurb about traffic NOT destined > >>for the LoopBack Interface itself will be routed to 'ye old trashcan' > >> > >i.e., > > > >>Null Interface. > >> > >>Somebody please tell me that I can send traffic from one end of the > >> > >circuit > > > >>to the other and have it destined for a node OTHER than the Loopback > >>Interface with that node being on the same subnet as the Loopback > >> > >interface. > > > >>Thanks. > >> > >>Mark Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=38250&t=37933 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
