new distrubution layer design

[carl_townshend]

Hi all, we are in process of designing a new distrubution layer for the servers etc, however we have 2 computer rooms. we want to use layer 3 between the distribution and core. But we want to keep the same ip subnets in both computer rooms for the servers etc. What would we do here? use the dist switches as a gatway for the servers, using hsrp,vrrp etc? then would we link the 2 dist switches direct together using layer 2 or 3, I would think layer 2 so we can have the same subnets still in both rooms? then would we use l3 ports to the core switch say on a /30 network and advertise the vlans etc from the dist switches?

can anyone tell me the best design for this?

cheers

[carl_townshend]

hi there, i see what your saying but, the only thing is, if the return traffic is load balanced back to the dist routers, will some of the packets go to the other dist router and never reach the client? hope you know what i mean ? i.e both dist routers will be advertising the same vlans and ip networks, not different.

cheers

[ronbuchalski]

Carl, what is the other dist router?

-rb

[ronbuchalski]

Carl,

If a packet is routed to a router, and the router has an interface directly connected to the destination network, it will not route the packet to another router. Instead, it will arp for the destination host and then deliver the packet to the connected network.

You still seem to be confused by this fact.

-rb

[carl_townshend]

Hi , I understand that, but what im saying is that we have 2 distribution routers, 1 active one standby, these connect to the core routers via ospf, I want to know how come the traffic manages to get back to the client as it is load balanced back from the core to the non active distribution router also.

cheers

[ronbuchalski]

Carl, your comments indicate that you still do not understand what I have been trying to explain to you.

I will try one more time to explain this, using a more 'personal' example...

You have a letter to mail. There are two mail carriers, named 'Act' (for Active) and 'Stan' (for Standby), standing side by side, waiting to accept your mail. As you approach, you hear them repeatedly telling each other, "I'm alive". When you hand off the letter, Mail Carrier 'Act' tells you, "I'll take that" and accepts the letter from you. THIS IS HSRP.

Meanwhile, two bags of letters are delivered to the mail carrier's area, and one bag is given to each mail carrier. As they each look through their individual mail bags, they find letters addressed to you. BOTH of the mail carriers independently deliver these letters to you as they find them. They work totally independent from each other, and do not tell each other that they are delivering letters to you. THIS IS LOAD BALANCED ROUTING.

I hope this helps you to understand what I have been posting.

-rb

[carl_townshend]

hi there, I know what load balanced routing is, the question was more of what the other distribution router does with the packet, i think as it arrives to the other dist router, the interface is on the same subnet as the client and would just use arp to resolve the client, it would use the link in between the dist routers to get there as the other direct link would be blocked by spanning tree in my config, i think i know what happens now

thanks for your help

[ronbuchalski]

Carl, that is correct. From a spanning tree perspective, the frames sent from the distribution routers will be sent to the spanning tree root first and then down the appropriate branch. So the non-root dist. switch will send the frames across the interconnecting link to the root dist. switch.

-rb