Date: Sat, 8 Apr 2000 20:28:07 -0500 (CDT) From: Joe Greco <jgreco@ns.sol.net> To: javier@nyi.net (Javier Frias) Cc: dev@inetu.net, isp@freebsd.org Subject: Re: flat network Message-ID: <200004090128.UAA92724@aurora.sol.net> In-Reply-To: <38ECE636.CE86D01C@nyi.net> from Javier Frias at "Apr 6, 2000 3:32: 6 pm"
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> I've had quite a bid different experience with vlans. > At least on catalyst switches. Don't talk to me about Catalyst switches. Not today. Cisco sucks. > with vlans, arp is reduced. ARP works by broadcasting a packet to all > hosts attached > to an Ethernet segment. Since a vlans virtually reduces the number of > hosts > on each "Ethernet Segment" or "vlan", the number of host an arp request > reaches > is smaller. You're not talking to an idiot. With routing protocols, ARP is reduced further, to the point where the only ARP traffic on the network is for the physical interfaces present on the network. If you have one router and one machine on a network, with ARP you still have the potential to have as many ARP entries as you do virtual servers. If you would like a practical demonstration of why this is bad, go generate about 65,000 virtual servers on such a machine, and then ask for stuff from all of them. Note the behaviour of the ARP cache on your routers and switches. The behaviour is O(N), and you are screwed when N exceeds the capacity of the ARP table on the device. God forbid you've more than one server on the net! If you have one router and one machine on a network, with OSPF you have exactly two ARP entries - and no need for the router to ARP for each virtual server. If you would like a practical demonstration of why this is good, do the same test as above. The behaviour is O(1). > To move servers between facilities you need a flat network? you can move > vlans accross > switches. Plus, there are quite a large nmber of ways you can do this, > without > the need of a huge flat network. I wasn't proposing the creation of a huge flat network. My largest production network has a netmask of 0xfffffff0. I move servers between facilities with no problems, thanks to OSPF. Do a traceroute to both dns1.sol.net and dns2.sol.net, numbered right next to each other, for a trivial example. > vlans also offer quite a big more security than a flat network. > crosstalk is almost eliminated. > > In the isp market, how some companies provide colocation > without giving a customer a separate vlan is beyond my comprehesion. Use a separate routed network. Broaden your horizons. -- ... Joe ------------------------------------------------------------------------------- Joe Greco - Systems Administrator jgreco@ns.sol.net Solaria Public Access UNIX - Milwaukee, WI 414/342-4847 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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