Vlan + DHCP Scopes + 4506

[jdl508]

Hello,
I have a few questions. I am redesigning our outdated network to reflect our current growth etc. We will be going from a flat network of 100 users to a vlan seperated network of 30-45 users per vlan with 6-7 vlans. This will be spread out over 2 buildings less than 100 ' apart connected with fiber.
Question 1 is if I have a flat lan now with 100 users on dhcp how can i redistribute dhcp to the seperate vlans? I'm assuming I will setup a scope for each vlan but how will the server know which subnet gets what scope? I am also assuming i will just add the ip helper-address cmd to each vlan.
Q. 2 is My plan is to have a 4506 in the server room as a core switch and then have 2950T 48 on each floor. Having each floor connected to a GB backbone going to the 4506 (with a 48 port 1000baseT blade). Any ideas or comments on how this will work going through the fiber buildg to building. All the L3 switching will be at th 4506 so If a user needs something on a floor under them they will need to traverse the fiber and come back. Of course 99% of the time they will need to go to the fiber anyway to get to the servers. Any comments or questions are greatly appreciated.

 

[baddos]

Your design is good....

To solve your DHCP problem, put your DHCP server in your server VLAN with as many scopes are your VLANs. Then on the user VLANs, put the "ip helper xxx.xxx.xxx.xxx" in your 4506's configuration for the vlan. Replace xxx.xxx.xxx.xxx with the IP address of your DHCP server.

Basically taking a layer3 approach for each floor is good.

 

[bythespy]

Your layer 3 approach per floor is a solid idea and should work fine. Unless your users are move multigigabit files you should not have any problems.

On the vlan issue:
I am not familiar with the 4000 series but I am assuming it has a layer two capability much like the MSFCs in my 6509s. You will build your VLAN interfaces here. To simplify the explanation; you will build 6 or 7 vlan interfaces, these will serve as the router for the vlan and the default gateway. When a PC in vlan 4 requests a dhcp address it will pass through the VLAN interface for VLAN in route to the DHCP server. The server will assing an ip address based on the ip address of the VLAN interface.

On the 2950 you will assign each interface to a vlan, if you are doing voice you should also assign an alternate or voice vlan.

You mentioned 6 or 7 vlans in two buildings, but you did not indicate how many 2950s you will be using, but I am assuming one per vlan. It really does not matter, but multiple vlans per switch complicates the config and you have to make sure users do not move their workstations around.

so here goes:

pc x plugged in to a port on one of the 2950s the port is assigned to vlan 4. Therefore the DHCP request from the PC will pass through the VLAN interface 4 on the 4506.

Interface vlan 4 has an ip address of 10.0.4.1
Interface vlan 5 has 10.0.5.1

You have scopes setup for 10.0.4.0 and 10.0.5.0

When the DHCP requests passes through the interface vlan 4 it will receive an address from the vlan 4 scope based on the address assigned to the vlan interface.

This is very simplified, i know but maybe it will get the idea accross.

Goodluck!


Mspivey
CCNP

Have you been to

http://www.ciptug.org

?
The OFFICIAL Cisco IP Telephony User Group!

"convergence isn't coming...... it is here." mspivey 2003

 

[jdl508]

Appreciate the responses. It sounds like everything is going to line up properly, just needed that warm & fuzzy before I ordered the equipment. The big thing for me is not the vlan L3 switching but how it will play through the fiber to the other building. I'm assuming / hoping that the fiber will literally be transparent to the cisco boxes. Also to give a little more info yes we are using 1 2950T 48 per floor, with no ip phones. Thats a whole other story
Thanks
jdl

 

[bythespy]

You will have a fiber gbic blade in the 4506 correct?

You will have a fiber gbic in each 2950 correct?

You will set these ports up as trunk ports on each end and it will be just like a normal ethernet port.

Don't get hung up on fiber vs copper, to the switch it is just faster ethernet.

Mspivey
CCNP

Have you been to

http://www.ciptug.org

?
The OFFICIAL Cisco IP Telephony User Group!

"convergence isn't coming...... it is here." mspivey 2003

 

[baddos]

Also... If you haven't order the chassis yet, you might want to look at the 4507 instead of the 4506. The 4507 will allow you to put an additional supervisor module in for redundancy.

 

[jdl508]

Actually the building will ahve fiber connecting it but the GB uplink ports will all be copper based. Basically the elec engineer will have a patch panel in each building were the fiber will terminate to copper. I will have a couple GB 48 port blades in the 4506 that i will do ethercahnnel to each switch GB port = 2gb backbone to every floor. That is the plan at least. Baddos I was thinking about the redundant supervisor since if that goes there is NO communication between floors. It may be worth the money instead of having a single point of failure. Have to see what the big boys upstairs say about that one.
Thanks

 

[baddos]

You could also just buy the 4507 chassis w/ only one supervisor this year, and get the second supervisor next year.

I'm a little concerned about your telco guy using media converters, to change the fiber to 1gb copper. Why not just through a fiber patch panel in front of your 4500 switch and buy a gbic blade? Definately less to go wrong than dealing with media converters.

 

[bythespy]

I agree, stay away from media conversion.

how many 2950 switches will you have in production?

Mspivey
CCNP

Have you been to

http://www.ciptug.org

?
The OFFICIAL Cisco IP Telephony User Group!

"convergence isn't coming...... it is here." mspivey 2003

 

[jdl508]

I will be looking at around 3 2950 48 port in the far building and another 3 in the main building. The prob is that the new building is being built and this has all been spec'd out already. I asked the other day and it looks like its to late to change the media converters. What is the problem with them? Just another link to break or are the problematic by nature?
Thanks

 

[baddos]

I've had reliability problems with them before in the past, but that was with 100mb versions. Generally speaking though, if you can go direct to the switch without any conversions your better off.

 

[bythespy]

I assume you will be terminating the fiber to the media converters in close proximity to the switch? I am also hopeful that you do not already have the copper GBICs.

The fiber link between the switchs will give you more bandwidth and will be a more reliable solution.

If the three switches will be close to each other you can use the 100mb copper gbic with the 50mm yellow cable for linking them together.

Did you consult cisco on this design?



Mspivey
CCNP

Have you been to

http://www.ciptug.org

?
The OFFICIAL Cisco IP Telephony User Group!

"convergence isn't coming...... it is here." mspivey 2003

 

[jdl508]

Thanks for the responses! Picture this; 2 buildings approx 100 ft apart. Undergound fiber terminated 10 ft into each building so I will have at least another 100 ft of GB copper to the core switch from the media converters. The only reason I dont have GBIC's is because I am using 2950 that have fixed 1000baseT copper uplink ports. The model is 2950T 48. I did consult a cisco engineer working for a var and he was ok with this design as a matter of fact he recommended the fixed port 2950 switches. I'm going to setup another call to cisco and see what they say about the media converters. As far as connecting all the switches to the fiber or core switch I was planning on using cat6 for all the GB over copper backbone. Just do an etherchannel on the GB uplink ports and hopefully get 2GB to each floor. It is a star pattern to the core.
Thanks again

 

[baddos]

Wow... Only 10' in the building? I guess your stuck with media converters either way.

It should work fine, it's just not preferred.

 

[lui3]

The real question here is what is your plan for voice over ip and multimedia in the future. if there is any chance get the 4507r with the SUPIV/V blade. you could save money on the chassis and get the 4503 with a SupIV/V and a couple gbic blades.

don't forget the 48 10/100/1000 blades in the 4500 all share a 6 port gbic controller 8 ports to each gbic. they are all oversubscribed. thats why cisco only offers the 6 port gbic fiber module non blocking

stay away from fiber media converters. get gbics in the switches. better yet get 3550 smi in the closets or 2970s.

 

[Lequang]

What we did is:

Instead of 1x 2950/48 port, we stack 2x2950/24ports per floor. The stack has 2 GB/FO uplinks to Core Switch. So we have half floor still working if one 2950 fail.

Your config will work (because we did the same).

 

[jdl508]

Thanks for the replies, As for VoIP we will be doing it but with ip phones only at remote sites so this shouldnt be an issue with this switching infrastructure. I'm glad to hear that this similar config worked for you Lequang. We still havent ordered the switches but will be in the next couple weeks.
Thanks

 

[lui3]

another solution is to put a 2970 10/100 switch in each closet with an sfp gbic back to the core. then buy 2950T w/1000baseT ports to plug into the 2970. this way you have nice scalability and power in the switch architecure.