From my perspective... ...a physical mesh requires too many ports to be economical.
...a logical mesh has a couple of things against it. It requires a lot of configuration, and each router will be connected with a trunk interface, (on the antique switches I've worked with) every trunk will carry all the traffic in the switch, your maximum bandwidth across the whole switch is 1gbps, instead of the next option which gives you more bandwidth across the switch. ...two connections (non-trunked!) from each router to seperate switches, with each switch having a separate /29 or /28 for connected devices and a fast-responding IGP running between the 5 routers gives you the most bang-for-the-buck in terms of throughput and failure responsiveness. With non-trunked interfaces, the switches can actually switch, and you can squeeze more than 1gbps of bandwidth through it. Even if you don't have that much traffic, you still have less latency (ok, it's an infestimally tiny amount, but every little bit helps.) If a switch completely fails and the ethernet ports of the connected routers go down/down, your IGP triggers and you have a fast failover. If a switch fails and the ethernets stay up/up, you have a slow failover, based on the timers of your IGP. Ejay Hire
-----Original Message----- From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu] On Behalf Of Scott Weeks Sent: Friday, February 24, 2006 8:03 PM To: nanog@merit.edu Subject: Transit LAN vs. Individual LANs
I have 2 core routers (CR) and 3 access routers (AR) currently connected point-to-point where each AR connects to each CR for a total of 6 ckts. Now someone has decided to connect them with Gig-E. I was wondering about the benefits or disadvantages of keeping the ckts each in their own individual LANs or tying them all into one VLAN for a "Transit LAN" as those folks that decided on going to Gig-E aren't doing any logical network architecting (is that a real word?).
Anyone got any suggestions, comments or helpful hints?
Thanks, scott