Reasons for OSPF on edge switches. Have anybody know one? (Easy Points!)

[Sergej Gurenko]

Today all vendors are pushing intellectual switches to the edge. A lot qos, access control and routing can be done as close to the user PC as possible. Have anybody know reasons to push/configure OSPF on the edge switches.
My opinion is it much ease to configure all access lists and routing on two core (or in big network distribution switches).
Can you please point me to the new millennium switched network design guides. I wont to find more reasons to enabling (and promoting) ospf on customer edge switches (Procurve series)
Thanks!
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Network Engineer, CCNP2.0/CCNP3.0

[Gonzo Granello · Accepted solution]

Sergej,

that is indeed a tough one.... :-) Let me start with OSPF or routing on the "edge" in general. My opinion is that most scenarios of edge routing are something I would avoid because of the administration issues that arise. Unless you utilize a lot of automation - and give up control for that matter!! - it is not desireable to route in every switch except for the instances where routing is not the main competency of a manufacturer - hence cannot be concentrated in one spot and the performance loss is easier to take distributed. (hint) As far as QOS concerns, there you want to have everything DONE on the edge (like a phone sets all bits correct) before it hits the switch or router. If it is done correct, the switch / router will not be bothered with classifing or remarking packets and therefore your network will actually do what it is supposed to do. Forward traffic vs. being a network data storage...... Now you just need to seperate the nice all wonderful marketing world from real life and you know what i'm talking about. Not to forget that all Admins are lazy of course.

Hope that helps, I will gladly answer your questions.

GG

[Les Ligetfalvy]

Not all organizations have their networks or their support staff with a single strong central core. I am DivIT in my organization and CorpIT has no involvement at all in how my network is laid out. The demarcation is at the WAN router.

Divisions decide whether or not to subnet based on local requirements. Some divisions do and some don't. What you might consider an edge switch may be considered a core switch by others. What you may consider as a difficulty to manage at the edge could be normal delegation by others.

This is not a "one size fits all" market.

[Regnar Bang Lyngsø_2]

I don't do OSPF to the edge, but probably I could come up with a few cases.

Case one:
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Assume that I have on access switch connected to two different distribution switches. I *could* use OSPF to obtain load sharing on the two links (probably I would make some stupid mistake with spanning trees along the way - or use Cisco equipment with PVST).

Case two:
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I have a critical application running on *nix, that for some bizarre reason can't be run of a server in my server room. Using OSPF with zebra/quagga/gated I connect my host to two different switches. [Bad case - you might as well have the distribution/core L3 device communicate with the end station]

Case three:
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I hate troubleshooting L2 paths. Gimme ping, gimme traceroute, gimme 'sh ip route'.

Access lists:
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If you are not running Cisco equipment with DHCP snooping you might use access-lists to minimize the risk of having rogue DHCP servers hanging around. This is a nice thing to do at the edge.
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Network bum