Mark, You can _advertise_ the whole subnet, but the problem is that once you assign a subnet to the loopback, you cannot assign another interface an IP address in the same address space. I'm still not sure I understand what your trying to accomplish here. If you have hosts that will have IP addresses, they'll have to be able to talk to the router using their IP addresses, which means the router will have to have an interface in the devices subnets. I don't see what the loopback buys you that simply assigning a secondary IP address to the ethernet interface does not.
-Kent -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Mark Odette II Sent: Thursday, March 14, 2002 12:23 PM To: [EMAIL PROTECTED] Subject: RE: Loopback Interfaces..long reply, read carefully please to [7:38285] OK, For some reason, my first time of sending this reply got chopped, so here it is again. Brian, et al., Please Note the following: ***All I wanted to know was: Can the Loopback Interface be used to host a complete subnet (and the Router make routing decisions with this inteface), or is its functionality such that it will always respond like an interface configured with a 255.255.255.255 mask, and 86 traffic not destined for IT on the same subnet?? I'm not looking for someone to help me make a completely working config for all routers in this implementation. The idea is to do such: !Interface FastEthernet0 ! description Connected to PIX Outside Interface, and PIX Inside Interface is subnet for Data traffic. ! Ip adress x.x.x.x 255.255.255.x !Interface Loopback0 ! description VoIP subnet with VoIP originating/terminating on this Router... other hosts also placed on the same subnet at a later date, and connecting via the Ethernet Port which connects to a switch that the other hosts are also plugging into. ! Ip address 192.168.101.1 255.255.255.0 !Interface Serial0 ! NO IP ADDRESS ! Encap Frame-Relay !Interface Serial0.1 ! description Connected to the Internet ! Ip address x.x.x.x x.x.x.252 ! interface-dlci 16 !Interface Serial0.100 ! description Connected to HQ over PVT FR for Voice traffic ! ip unnumbered loopback0 ! interface-dlci 100 ! {insert Map-Class Tag here} !{Insert Route-Maps Here} !{Insert Voice configuration here... a.k.a. Dial Peers} !{Insert QoS config here... a.k.a. Map Classes} !Router EIGRP 1750 !Network 192.168.100.0 >>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=38335&t=38335 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
