We are currently creating all our VLANS on our core (6513 sup2 720). One of our VLANS has over 19 class c subnets on it. Last week after a power outage, the core's processor went up to 92% until I looked on the wire and saw that DHCP was going mad! We restarted the DHCP service and all was well again.
The DHCP server is in the VLAN that has all those subnets. I'm trying to convince my boss that it is wise to move all the vlans out to the edge onto the distribution switches and have a set of VLANS per building.
I'm sure my preferred scenario would have stopped this problem, which I think was a massive broadcast storm.
Would you all agree?
Yeah that makes sense to me. That is the scenario I would like to put in place, it's just convincing my colleague now!!
So, 1 /24 VLAN per floor, then you split that VLAN into 2 /25. I missing something again here, if you create the vlan on the 6500 "ip address 192.168.1.1 255.255.255.0. How are you then splitting this up into 2 /25?
Sorry to be a pain.
Sorry, posted before you edited this post.
You don't create the vlan ip address of 192.168.1.1 255.255.255.0. Instead you would have for example 2 vlans per floor - vlan 10 & 11. On the 6500 switch
int vlan 10
ip address 192.168.1.1 255.255.255.128
int vlan 11
ip address 192.168.1.129 255.255.255.128
Don't get too sidetracked with /24 vs /25. There is nothing wrong with a /24 and a lot of networks use this as standard.