A sample config with secondary ip addresses might look like: int e0 ip address 10.1.2.1 255.255.255.0 secondary ip address 10.1.1.1 255.255.255.0
If you were to connect a hub to that interface you could assign connected PCs to either subnet. Those PCs could communicate with each other. If you have the equipment, create a small lab to verify this. If the same scenario as above were repeated, but this time a switch was substituted for the hub - it would still work. All switch ports would be in the same VLAN. The switch is clueless about the ip addressing of the PCs. While this is possible - it is not best design practice. Larry's prior post also mentioned using trunking between the router and switch. In that case, the switch would be divided into "virtual switches" by assigning groups of switch ports to seperate VLANs. PCs associated with different VLANs cannot communicate without benefit of a routing function. Usual practice is to associate an ip subnet with a VLAN. If there were two VLANs and the local router had two or more Ethernet interfaces then a switch port from each VLAN could be connected to its own router interface. Nothing fancy here. Not much different from two hubs. As the number of VLANs grew it would chew up switch and router ports. Read 'gets expensive fast.' Again, if you have the equipment - try it. A better solution is to use trunking. One switch port is connected to one router port. aka "Router on a stick." The switch port is configured to do trunking. Encapsulation is determined. The router interface would be configured with subinterfaces corresponding to the various subnets and their associated VLANs. The encapsulation would match that configured on the switch. My guess is this is the solution desired by Ricky's boss. > -----Original Message----- > From: mlh [mailto:[EMAIL PROTECTED]] > Sent: Friday, March 29, 2002 10:17 PM > To: [EMAIL PROTECTED] > Subject: Re: Router question.. [7:39788] > > > how to use secondary ip address or sub-interface routing 3 > different and > separate LANs? how the 3 LANs connect to one interface of a router ? > > Thank you. > > mlh > > > ----- Original Message ----- > From: "Roberts, Larry" > To: > Sent: Friday, March 29, 2002 12:46 AM > Subject: RE: Router question.. [7:39788] > > > > Several ways. > > > > Sub-interfaces and inter-vlan routing ( 802.1q or isl ) or > the less secure > > but easier way of just using secondary IP's on the Ethernet > interfaces. > > > > Thanks > > > > Larry > > > > -----Original Message----- > > From: Ricky Chan [mailto:[EMAIL PROTECTED]] > > Sent: Thursday, March 28, 2002 12:43 PM > > To: [EMAIL PROTECTED] > > Subject: Router question.. [7:39788] > > > > > > Hi all, > > > > My boss just come up and give me a senario question like > this. He told me > > that I owned a company which uses 3 different LANs, for example, > > 172.27.10.x, 172.27.11.x, 172.27.12.x. But I only have one > cisco 2600 > series > > router and 2900 series switch. I can't use the serial ports from the > router. > > Just the two ethernet ports (by default). My question is, > is it possible? > > Please advice. > > > > Thanks > > > > Ricky Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=39936&t=39788 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
