nanog mailing list archives
Re: Router with 2 (or more) interfaces in same network
From: "Stewart, William C (Bill), RTSLS" <billstewart () att com>
Date: Tue, 11 Nov 2003 17:03:26 -0600
While it's a more common thing to do with hosts, there are a number of reasons you might want a router with multiple interfaces on the same network. - Sometimes ugly things happen during reconfigurations, e.g. replacing two routers with one bigger one. Load balancing is more likely to want two interfaces with the same IP address, but sometimes different addresses on the same subnet makes more sense. - Security monitoring / eavesdropping applications, where one interface is listen-only or listen-mostly. Usually promiscuous interfaces are enough to do this, but there are remote monitoring applications where it might help. - You may want different policies on the two interfaces, and sometimes it's easier to do that with separate IP addresses than differentiate by TCP ports or whatever (e.g. VOIP on one interface, regular traffic on another, with a LAN switch keeping them separate.) That's especially believable if you're using an ISP that doesn't do Type of Service bits, or multiple ISPs that don't peer with ToS. - Ugly loopback thingies working around other limitations. I've mostly seen this at Layer 2, with Cisco Virtual Trunking, or building things in test labs.
Current thread:
- Re: Router with 2 (or more) interfaces in same network, (continued)
- Re: Router with 2 (or more) interfaces in same network Neil J. McRae (Nov 12)
- Re: Router with 2 (or more) interfaces in same network Stephen J. Wilcox (Nov 12)
- RE: Router with 2 (or more) interfaces in same network Shawn Solomon (Nov 11)
- Re: Router with 2 (or more) interfaces in same network Paul S. Brown (Nov 11)
- RE: Router with 2 (or more) interfaces in same network Lucas Iglesias (Nov 11)
- Re: Router with 2 (or more) interfaces in same network Frank Louwers (Nov 11)
- RE: Router with 2 (or more) interfaces in same network Peter John Hill (Nov 11)
- RE: Router with 2 (or more) interfaces in same network Lucas Iglesias (Nov 11)
- RE: Router with 2 (or more) interfaces in same network Truman, Michelle, RTSLS (Nov 11)
- RE: Router with 2 (or more) interfaces in same network Michel Py (Nov 11)
- Re: Router with 2 (or more) interfaces in same network Stewart, William C (Bill), RTSLS (Nov 11)